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A complex expression is specified in Maxima by adding the real part of the
expression to %i times the imaginary part. Thus the roots of the
equation x^2 - 4*x + 13 = 0 are 2 + 3*%i and 2 - 3*%i.
Note that simplification of products of complex expressions can be effected by
expanding the product. Simplification of quotients, roots, and other functions
of complex expressions can usually be accomplished by using the realpart,
imagpart, rectform, polarform, abs, carg
functions.
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bfloat replaces integers, rationals, floating point numbers, and some symbolic constants
in expr with bigfloat (variable-precision floating point) numbers.
The constants %e, %gamma, %phi, and %pi
are replaced by a numerical approximation.
However, %e in %e^x is not replaced by a numeric value
unless bfloat(x) is a number.
bfloat also causes numerical evaluation of some built-in functions,
namely trigonometric functions, exponential functions, abs, and log.
The number of significant digits in the resulting bigfloats is specified by the
global variable fpprec.
Bigfloats already present in expr are replaced with values which have
precision specified by the current value of fpprec.
When float2bf is false, a warning message is printed when
a floating point number is replaced by a bigfloat number with less precision.
Examples:
bfloat replaces integers, rationals, floating point numbers, and some symbolic constants
in expr with bigfloat numbers.
(%i1) bfloat([123, 17/29, 1.75]);
(%o1) [1.23b2, 5.862068965517241b-1, 1.75b0]
(%i2) bfloat([%e, %gamma, %phi, %pi]);
(%o2) [2.718281828459045b0, 5.772156649015329b-1,
1.618033988749895b0, 3.141592653589793b0]
(%i3) bfloat((f(123) + g(h(17/29)))/(x + %gamma));
1.0b0 (g(h(5.862068965517241b-1)) + f(1.23b2))
(%o3) ----------------------------------------------
x + 5.772156649015329b-1
bfloat also causes numerical evaluation of some built-in functions.
(%i1) bfloat(sin(17/29)); (%o1) 5.532051841609784b-1 (%i2) bfloat(exp(%pi)); (%o2) 2.314069263277927b1 (%i3) bfloat(abs(-%gamma)); (%o3) 5.772156649015329b-1 (%i4) bfloat(log(%phi)); (%o4) 4.812118250596035b-1
Returns true if expr is a bigfloat number, otherwise false.
Default value: false
bftorat controls the conversion of bfloats to rational numbers. When
bftorat is false, ratepsilon will be used to control the
conversion (this results in relatively small rational numbers). When
bftorat is true, the rational number generated will accurately
represent the bfloat.
Note: bftorat has no effect on the transformation to rational numbers
with the function rationalize.
Example:
(%i1) ratepsilon:1e-4;
(%o1) 1.0e-4
(%i2) rat(bfloat(11111/111111)), bftorat:false;
`rat' replaced 9.99990999991B-2 by 1/10 = 1.0B-1
1
(%o2)/R/ --
10
(%i3) rat(bfloat(11111/111111)), bftorat:true;
`rat' replaced 9.99990999991B-2 by 11111/111111 = 9.99990999991B-2
11111
(%o3)/R/ ------
111111
Default value: true
bftrunc causes trailing zeroes in non-zero bigfloat numbers not to be
displayed. Thus, if bftrunc is false, bfloat (1)
displays as 1.000000000000000B0. Otherwise, this is displayed as
1.0B0.
Returns the number of bits of precision in a bigfloat number. This
value depends, of course, on the value of fpprec.
(%i1) fpprec:16; (%o1) 16 (%i2) bigfloat_bits(); (%o2) 56 (%i3) fpprec:32; (%o3) 32 (%i4) bigfloat_bits(); (%o4) 109
Returns the smallest bigfloat value, eps, such that
1+eps is not equal to 1. The value depends on fpprec,
of course.
(%i1) fpprec:16; (%o1) 16 (%i2) bigfloat_eps(); (%o2) 1.387778780781446b-17 (%i3) fpprec:32; (%o3) 32 (%i4) bigfloat_eps(); (%o4) 1.5407439555097886824447823540679b-33
decode_float takes a float f and returns a list of three
values that characterizes f, which must be either a float
or bfloat. The first value has the same type as f, but
is a number in the range [1, 2). The second value is an
exponent. The third value is a float of the same type as f and
has the value of 1 if f is greater than or equal to 0;
otherwise, -1.
If the returned list is [mantissa, expo, sign], then
scale_float(mantissa, exp)*sign is identical to f.
(%i1) decode_float(4e0); (%o1) [1.0, 2, 1.0] (%i2) decode_float(4b0); (%o2) [1.0b0, 2, 1.0b0] (%i3) decode_float(%pi); decode_float is only defined for floats and bfloats: %pi -- an error. To debug this try: debugmode(true); (%i4) decode_float(float(%pi)); (%o4) [1.570796326794897, 1, 1.0] (%i5) decode_float(1.1e-5); (%o5) [1.441792, - 17, 1.0] (%i6) %[1]*2^%[2]; (%o6) 1.1e-5
This is a relatively simple interface to Common Lisp
decode_float. However we return a signficand in the range
[1,2) instead of [0.5, 1). The former matches
IEEE-754. Of course, this is extended to support bfloats.
Returns true if expr is a literal even integer, otherwise
false.
evenp returns false if expr is a symbol, even if expr
is declared even.
Converts integers, rational numbers and bigfloats in expr to floating
point numbers. It is also an evflag, float causes
non-integral rational numbers and bigfloat numbers to be converted to floating
point.
Default value: true
When float2bf is false, a warning message is printed when
a floating point number is replaced by a bigfloat number with less precision.
Returns the number of bits of precision of a floating-point number.
Returns the smallest floating-point value, eps, such that
1+eps is not equal to 1.
Returns the number of bits of precision of a floating-point number,
which can be either a float or bigfloat. This is basically the number
of bits used to represent the mantissa of a floating-point number.
For floats, this is 53 (for IEEE double-floats), but can be less when
denormal numbers occur. For bigfloats, this is equal to
fpprec, when converted from digits to bits.
Returns the sign of f. It is +1 or -1 of the same type as f. It is an error if f is not a float or bigfloat. Note that some lisps do not support signed zeros for floating-point numbers. Bigfloats do not support signed zeroes. The examples below assume signed zeroes are supported.
(%i1) float_sign(1.0); (%o1) 1.0 (%i2) float_sign(-5.0); (%o2) - 1.0 (%i3) float_sign(-0.0); (%o3) - 1.0 (%i4) float_sign(1b0); (%o4) 1.0b0 (%i5) float_sign(-5b0); (%o5) - 1.0b0 (%o6) float_sign(-0b0); (%o6) 1.0b0 (%i7) float_sign(%pi); float_sign is only defined for floats and bfloats: %pi -- an error. To debug this try: debugmode(true);
Returns true if expr is a floating point number, otherwise
false.
Default value: 16
fpprec is the number of significant digits for arithmetic on bigfloat
numbers. fpprec does not affect computations on ordinary floating point
numbers.
See also bfloat and fpprintprec.
Default value: 0
fpprintprec is the number of digits to print when printing an ordinary
float or bigfloat number.
For ordinary floating point numbers,
when fpprintprec has a value between 2 and 16 (inclusive),
the number of digits printed is equal to fpprintprec.
Otherwise, fpprintprec is 0, or greater than 16,
and the number is printed "readably":
that is, it is printed with sufficient digits to exactly reconstruct the number on input.
For bigfloat numbers,
when fpprintprec has a value between 2 and fpprec (inclusive),
the number of digits printed is equal to fpprintprec.
Otherwise, fpprintprec is 0, or greater than fpprec,
and the number of digits printed is equal to fpprec.
For both ordinary floats and bigfloats,
trailing zero digits are suppressed.
The actual number of digits printed is less than fpprintprec
if there are trailing zero digits.
fpprintprec cannot be 1.
Returns true if expr is a literal numeric integer, otherwise
false.
integerp returns false if expr is a symbol, even if expr
is declared integer.
Examples:
(%i1) integerp (0); (%o1) true (%i2) integerp (1); (%o2) true (%i3) integerp (-17); (%o3) true (%i4) integerp (0.0); (%o4) false (%i5) integerp (1.0); (%o5) false (%i6) integerp (%pi); (%o6) false (%i7) integerp (n); (%o7) false (%i8) declare (n, integer); (%o8) done (%i9) integerp (n); (%o9) false
integer_decode_float takes a float f and returns a list of three
values that characterizes f, which must be either a float
or bfloat. The first value is an integer. The second value is an
exponent. The third value is 1 if f is positive or zero;
otherwise, -1.
If the returned list is [mantissa, expo, sign], then
scale_float(fl(mantissa), expo)*sign is identical to f.
Here, fl is either float or bfloat depending on
whether f is a float or a bfloat.
(%i1) integer_decode_float(4.0); (%o1) [4503599627370496, - 50, 1] (%i2) integer_decode_float(4b0); (%o2) [36028797018963968, - 53, 1] (%i3) scale_float(float(%o1[1]), %o1[2]); (%o3) 4.0 (%i4) scale_float(bfloat(%o2[1]), %o2[2]); (%o4) 4.0b0 (%i5) integer_decode_float(4); decode_float is only defined for floats and bfloats: 4 -- an error. To debug this try: debugmode(true); (%i6) integer_decode_float(1e-7); (%o6) [7555786372591432, - 76, 1] (%i7) integer_decode_float(1b-7); (%o7) [60446290980731459, - 79, 1] (%i8) scale_float(float(%o6[1]), %o6[2]); (%o8) 1.0e-7
For lisps that support denormal numbers, we have the following results.
(%i1) integer_decode_float(least_positive_float); (%o1) [1, - 1074, 1] (%i2) integer_decode_float(100*least_positive_float); (%o2) [100, - 1074, 1] (%i3) integer_decode_float(least_positive_normalized_float); (%o3) [4503599627370496, - 1074, 1]
The number of bits in the integer part decreases as the denormal number decreases. Bfloat numbers do not have denormals because the exponent is not bounded.
This is a relatively simple interface to Common Lisp integer_decode_float. However, the integer part can vary depending on the Lisp implementation; we return the same value, independent of the Lisp implementation. Of course, this is extended to support bfloats.
is_power_to_two returns true if n is a power of
two and false otherwise. n may be an integer, a
rational, a float, or a big float.
Some examples:
(%i1) is_power_of_two(0); (%o1) false (%i2) is_power_of_two(4); (%o2) true (%i3) is_power_of_two(355/113); (%o3) false (%i4) is_power_of_two(1/32); (%o4) true (%i5) is_power_of_two(1048576); (%o5) true (%i6) is_power_of_two(1048575); (%o6) false (%i7) is_power_of_two(0.0); (%o7) false (%i8) is_power_of_two(1048576.0); (%o8) true (%i9) is_power_of_two(1048575.0); (%o9) false (%i10) is_power_of_two(1/256.0); (%o10) true (%i11) is_power_of_two(0b0); (%o11) false (%i12) is_power_of_two(1048576b0); (%o12) true (%i13) is_power_of_two(1048575b0); (%o13) false (%i14) is_power_of_two(1/256b0); (%o14) true
Default value: false
m1pbranch is the principal branch for -1 to a power.
Quantities such as (-1)^(1/3) (that is, an "odd" rational exponent) and
(-1)^(1/4) (that is, an "even" rational exponent) are handled as follows:
domain:real
(-1)^(1/3): -1
(-1)^(1/4): (-1)^(1/4)
domain:complex
m1pbranch:false m1pbranch:true
(-1)^(1/3) 1/2+%i*sqrt(3)/2
(-1)^(1/4) sqrt(2)/2+%i*sqrt(2)/2
Return true if and only if n >= 0 and n is an integer.
Returns true if expr is a literal integer, rational number,
floating point number, or bigfloat, otherwise false.
numberp returns false if expr is a symbol, even if expr
is a symbolic number such as %pi or %i, or declared to be
even, odd, integer, rational, irrational,
real, imaginary, or complex.
Examples:
(%i1) numberp (42);
(%o1) true
(%i2) numberp (-13/19);
(%o2) true
(%i3) numberp (3.14159);
(%o3) true
(%i4) numberp (-1729b-4);
(%o4) true
(%i5) map (numberp, [%e, %pi, %i, %phi, inf, minf]);
(%o5) [false, false, false, false, false, false]
(%i6) declare (a, even, b, odd, c, integer, d, rational,
e, irrational, f, real, g, imaginary, h, complex);
(%o6) done
(%i7) map (numberp, [a, b, c, d, e, f, g, h]);
(%o7) [false, false, false, false, false, false, false, false]
numer causes some mathematical functions (including exponentiation)
with numerical arguments to be evaluated in floating point. It causes
variables in expr which have been given numerals to be replaced by
their values. It also sets the float switch on.
See also %enumer.
Examples:
(%i1) [sqrt(2), sin(1), 1/(1+sqrt(3))];
1
(%o1) [sqrt(2), sin(1), -----------]
sqrt(3) + 1
(%i2) [sqrt(2), sin(1), 1/(1+sqrt(3))],numer; (%o2) [1.414213562373095, 0.8414709848078965, 0.3660254037844387]
Default value: false
The option variable numer_pbranch controls the numerical evaluation of
the power of a negative integer, rational, or floating point number. When
numer_pbranch is true and the exponent is a floating point number
or the option variable numer is true too, Maxima evaluates
the numerical result using the principal branch. Otherwise a simplified, but
not an evaluated result is returned.
Examples:
(%i1) (-2)^0.75;
0.75
(%o1) (- 2)
(%i2) (-2)^0.75,numer_pbranch:true; (%o2) 1.189207115002721 %i - 1.189207115002721
(%i3) (-2)^(3/4);
3/4 3/4
(%o3) (- 1) 2
(%i4) (-2)^(3/4),numer;
0.75
(%o4) 1.681792830507429 (- 1)
(%i5) (-2)^(3/4),numer,numer_pbranch:true; (%o5) 1.189207115002721 %i - 1.189207115002721
Declares the variables x_1, …, x_n to have
numeric values equal to expr_1, …, expr_n.
The numeric value is evaluated and substituted for the variable
in any expressions in which the variable occurs if the numer flag is
true. See also ev.
The expressions expr_1, …, expr_n can be any expressions,
not necessarily numeric.
Returns true if expr is a literal odd integer, otherwise
false.
oddp returns false if expr is a symbol, even if expr
is declared odd.
Default value: 2.0e-15
ratepsilon is the tolerance used in the conversion
of floating point numbers to rational numbers, when the option variable
bftorat has the value false. See bftorat for an example.
Convert all double floats and big floats in the Maxima expression expr to
their exact rational equivalents. If you are not familiar with the binary
representation of floating point numbers, you might be surprised that
rationalize (0.1) does not equal 1/10. This behavior isn’t special to
Maxima – the number 1/10 has a repeating, not a terminating, binary
representation.
(%i1) rationalize (0.5);
1
(%o1) -
2
(%i2) rationalize (0.1);
3602879701896397
(%o2) -----------------
36028797018963968
(%i3) fpprec : 5$
(%i4) rationalize (0.1b0);
209715
(%o4) -------
2097152
(%i5) fpprec : 20$
(%i6) rationalize (0.1b0);
236118324143482260685
(%o6) ----------------------
2361183241434822606848
(%i7) rationalize (sin (0.1*x + 5.6));
3602879701896397 x 3152519739159347
(%o7) sin(------------------ + ----------------)
36028797018963968 562949953421312
Returns true if expr is a literal integer or ratio of literal
integers, otherwise false.
scale_float scales the float f by the value
2^n. This is done carefully so that no round-off every
occurs. If f is a float, then it is possible to underflow to 0
or overflow, depending on the value of f and n. Bigfloats
cannot underflow or overflow.
(%i1) scale_float(2d0, 2); (%o1) 8.0 (%i2) scale_float(2d0, -2); (%o2) 0.5 (%i3) scale_float(-2d0, -10); (%o3) - 0.001953125 (%i4) scale_float(1d0, -2000); (%o4) 0.0 (%i5) scale_float(2b0, 2); (%o5) 8.0b0 (%i6) scale_float(1b0, -2000); (%o6) 8.709809816217217b-603 (%i7) scale_float(1, 5); scale_float: first arg must be a float or bfloat: 1 -- an error. To debug this try: debugmode(true); (%i8) scale_float(1.0, n); scale_float: second arg must be an integer: n -- an error. To debug this try: debugmode(true);
This is a relatively simple interface to Common Lisp scale_float. Of course, this is extended to support bfloats.
unit_in_last_place returns a value that is the gap between
n and the nearest other number. See, for example,
Kahan, FOOTNOTE 1. unit_in_last_place supports rational numbers,
floating-point numbers and bigfloat numbers. For integer, the result
is always 1, and for rational numbers the result is always 0.
The examples below assume IEEE-754 arithmetic that supports denormal numbers. Some lisps like Clisp do not have denormal numbers.
(%i1) unit_in_last_place(0); (%o1) 1 (%i2) unit_in_last_place(-123); (%o2) 1 (%i3) unit_in_last_place(2/3); (%o3) 0 (%i4) unit_in_last_place(355/113); (%o4) 0 (%i5) unit_in_last_place(0b0); (%o5) 0.0b0 (%i6) unit_in_last_place(0.0); (%o6) 4.940656458412465e-324 (%i7) unit_in_last_place(1.0); (%o7) 1.110223024625157e-16 (%i8) unit_in_last_place(1b0); (%o8) 1.387778780781446b-17 (%i9) unit_in_last_place(100.0); (%o9) 1.4210854715202e-14 (%i10) unit_in_last_place(100b0); (%o10) 1.77635683940025b-15 (%i11) fpprec:32; (%o11) 32 (%i12) unit_in_last_place(1b0); (%o12) 1.5407439555097886824447823540679b-33 (%i13) unit_in_last_place(100b0); (%o13) 1.972152263052529513529321413207b-31
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Next: Functions and Variables for Strings, Previous: Strings, Up: Strings [Contents][Index]
Strings (quoted character sequences) are enclosed in double quote marks "
for input, and displayed with or without the quote marks, depending on the
global variable stringdisp.
Strings may contain any characters, including embedded tab, newline, and
carriage return characters. The sequence \" is recognized as a literal
double quote, and \\ as a literal backslash. When backslash appears at
the end of a line, the backslash and the line termination (either newline or
carriage return and newline) are ignored, so that the string continues with the
next line. No other special combinations of backslash with another character
are recognized; when backslash appears before any character other than ",
\, or a line termination, the backslash is ignored. There is no way to
represent a special character (such as tab, newline, or carriage return)
except by embedding the literal character in the string.
There is no character type in Maxima; a single character is represented as a one-character string.
The stringproc add-on package contains many functions for working with
strings.
Examples:
(%i1) s_1 : "This is a string."; (%o1) This is a string.
(%i2) s_2 : "Embedded \"double quotes\" and backslash \\ characters."; (%o2) Embedded "double quotes" and backslash \ characters.
(%i3) s_3 : "Embedded line termination in this string."; (%o3) Embedded line termination in this string.
(%i4) s_4 : "Ignore the \ line termination \ characters in \ this string."; (%o4) Ignore the line termination characters in this string.
(%i5) stringdisp : false; (%o5) false
(%i6) s_1; (%o6) This is a string.
(%i7) stringdisp : true; (%o7) true
(%i8) s_1; (%o8) "This is a string."
Previous: Introduction to Strings, Up: Strings [Contents][Index]
Concatenates its arguments. The arguments must evaluate to atoms. The return value is a symbol if the first argument is a symbol and a string otherwise.
concat evaluates its arguments. The single quote ' prevents
evaluation.
See also sconcat, that works on non-atoms, too, simplode,
string and eval_string.
For complex string conversions see also printf.
(%i1) y: 7$
(%i2) z: 88$
(%i3) concat (y, z/2);
(%o3) 744
(%i4) concat ('y, z/2);
(%o4) y44
A symbol constructed by concat may be assigned a value and appear in
expressions. The :: (double colon) assignment operator evaluates its
left-hand side.
(%i5) a: concat ('y, z/2);
(%o5) y44
(%i6) a:: 123;
(%o6) 123
(%i7) y44;
(%o7) 123
(%i8) b^a;
y44
(%o8) b
(%i9) %, numer;
123
(%o9) b
Note that although concat (1, 2) looks like a number, it is a string.
(%i10) concat (1, 2) + 3; (%o10) 12 + 3
Concatenates its arguments into a string. Unlike concat, the
arguments do not need to be atoms.
See also concat, simplode, string and eval_string.
For complex string conversions see also printf.
(%i1) sconcat ("xx[", 3, "]:", expand ((x+y)^3));
(%o1) xx[3]:y^3+3*x*y^2+3*x^2*y+x^3
Another purpose for sconcat is to convert arbitrary objects to strings.
(%i1) sconcat (x); (%o1) x
(%i2) stringp(%); (%o2) true
Converts expr to Maxima’s linear notation just as if it had been typed
in.
The return value of string is a string, and thus it cannot be used in a
computation.
See also concat, sconcat, simplode and
eval_string.
Default value: false
When stringdisp is true, strings are displayed enclosed in double
quote marks. Otherwise, quote marks are not displayed.
stringdisp is always true when displaying a function definition.
Examples:
(%i1) stringdisp: false$
(%i2) "This is an example string."; (%o2) This is an example string.
(%i3) foo () :=
print ("This is a string in a function definition.");
(%o3) foo() :=
print("This is a string in a function definition.")
(%i4) stringdisp: true$
(%i5) "This is an example string."; (%o5) "This is an example string."
Next: Lists, Previous: Strings, Up: Data Types and Structures [Contents][Index]
%e represents the base of the natural logarithm, also known as Euler’s
number. The numeric value of %e is the double-precision floating-point
value 2.718281828459045d0. (See A&S eqn 4.1.16, A&S 4.1.17.)
false represents the Boolean constant of the same name.
Maxima implements false by the value NIL in Lisp.
The Euler-Mascheroni constant, 0.5772156649015329.... It is defined by (A&S eqn 6.1.3 and DLMF 5.2.ii) $$ \gamma = \lim_{n \rightarrow \infty} \left(\sum_{k=1}^n {1\over k} - \log n\right) $$
ind represents a bounded, indefinite result.
See also limit.
Example:
(%i1) limit (sin(1/x), x, 0); (%o1) ind
The least negative floating-point number in Maxima. That is, the
negative floating-point number closest to 0. It is approximately
-4.94065e-324, when
denormal numbers
are supported. Otherwise it is the same as
least_negative_normalized_float.
The least negative normalized floating-point number in Maxima. That is, the negative normalized floating-point number closest to 0. It is approximately -2.22507e-308.
The least positive floating-point number in Maxima. That is, the
positive floating-point number closest to 0. It is approximately
4.94065e-324, when
denormal numbers
are supported. Otherwise it is the same as
least_positive_normalized_float.
The least positive normalized floating-point number in Maxima. That is, the positive normalized floating-point number closest to 0. It is approximately 2.22507e-308.
The most negative floating-point number in Maxima. It is approximately -1.79769e+308.
The most positive floating-point number in Maxima. It is approximately 1.797693e+308.
%phi represents the so-called golden mean,
\((1+\sqrt{5})/2.\)
The numeric value of %phi is the double-precision floating-point value
1.618033988749895d0.
fibtophi expresses Fibonacci numbers fib(n) in terms of
%phi.
By default, Maxima does not know the algebraic properties of %phi.
After evaluating tellrat(%phi^2 - %phi - 1) and algebraic: true,
ratsimp can simplify some expressions containing %phi.
Examples:
fibtophi expresses Fibonacci numbers fib(n) in terms of %phi.
(%i1) fibtophi (fib (n));
n n
%phi - (1 - %phi)
(%o1) -------------------
2 %phi - 1
(%i2) fib (n-1) + fib (n) - fib (n+1);
(%o2) - fib(n + 1) + fib(n) + fib(n - 1)
(%i3) fibtophi (%);
n + 1 n + 1 n n
%phi - (1 - %phi) %phi - (1 - %phi)
(%o3) - --------------------------- + -------------------
2 %phi - 1 2 %phi - 1
n - 1 n - 1
%phi - (1 - %phi)
+ ---------------------------
2 %phi - 1
(%i4) ratsimp (%);
(%o4) 0
By default, Maxima does not know the algebraic properties of %phi.
After evaluating tellrat (%phi^2 - %phi - 1) and algebraic: true,
ratsimp can simplify some expressions containing %phi.
(%i1) e : expand ((%phi^2 - %phi - 1) * (A + 1));
2 2
(%o1) %phi A - %phi A - A + %phi - %phi - 1
(%i2) ratsimp (e);
2 2
(%o2) (%phi - %phi - 1) A + %phi - %phi - 1
(%i3) tellrat (%phi^2 - %phi - 1);
2
(%o3) [%phi - %phi - 1]
(%i4) algebraic : true;
(%o4) true
(%i5) ratsimp (e);
(%o5) 0
%pi represents the ratio of the perimeter of a circle to its diameter.
The numeric value of %pi is the double-precision floating-point value
3.141592653589793d0.
true represents the Boolean constant of the same name.
Maxima implements true by the value T in Lisp.
und represents an undefined result.
See also limit.
Example:
(%i1) limit (x*sin(x), x, inf); (%o1) und
zeroa represents an infinitesimal above zero. zeroa can be used
in expressions. limit simplifies expressions which contain
infinitesimals.
Example:
limit simplifies expressions which contain infinitesimals:
(%i1) limit(zeroa); (%o1) 0 (%i2) limit(x+zeroa); (%o2) x
zerob represents an infinitesimal below zero. zerob can be used
in expressions. limit simplifies expressions which contain
infinitesimals.
Next: Arrays, Previous: Constants, Up: Data Types and Structures [Contents][Index]
Next: Functions and Variables for Lists, Previous: Lists, Up: Lists [Contents][Index]
Lists are the basic building block for Maxima and Lisp. All data types
other than arrays, hashed arrays and numbers are represented as Lisp lists,
These Lisp lists have the form
((MPLUS) $A 2)
to indicate an expression a+2. At Maxima level one would see
the infix notation a+2. Maxima also has lists which are printed
as
[1, 2, 7, x+y]
for a list with 4 elements. Internally this corresponds to a Lisp list of the form
((MLIST) 1 2 7 ((MPLUS) $X $Y))
The flag which denotes the type field of the Maxima expression is a list itself, since after it has been through the simplifier the list would become
((MLIST SIMP) 1 2 7 ((MPLUS SIMP) $X $Y))
Next: Performance considerations for Lists, Previous: Introduction to Lists, Up: Lists [Contents][Index]
[ and ] mark the beginning and end, respectively, of a list.
[ and ] also enclose the subscripts of
a list, array, hashed array, or memoizing function. Note that
other than for arrays accessing the nth element of a list
may need an amount of time that is roughly proportional to n,
See Performance considerations for Lists.
Note that if an element of a subscripted variable is written to before
a list or an array of this name is declared a hashed array
(see Arrays) is created, not a list.
Examples:
(%i1) x: [a, b, c]; (%o1) [a, b, c]
(%i2) x[3]; (%o2) c
(%i3) array (y, fixnum, 3); (%o3) y
(%i4) y[2]: %pi; (%o4) %pi
(%i5) y[2]; (%o5) %pi
(%i6) z['foo]: 'bar; (%o6) bar
(%i7) z['foo]; (%o7) bar
(%i8) g[k] := 1/(k^2+1);
1
(%o8) g := ------
k 2
k + 1
(%i9) g[10];
1
(%o9) ---
101
Returns a single list of the elements of list_1 followed
by the elements of list_2, … append also works on
general expressions, e.g. append (f(a,b), f(c,d,e)); yields
f(a,b,c,d,e).
See also addrow, addcol and join.
Do example(append); for an example.
assoc searches for key as the first part of an argument of e
and returns the second part of the first match, if any.
key may be any expression.
e must be a nonatomic expression,
and every argument of e must have exactly two parts.
assoc returns the second part of the first matching argument of e.
Matches are determined by is(key = first(a))
where a is an argument of e.
If there are two or more matches, only the first is returned.
If there are no matches, default is returned, if specified.
Otherwise, false is returned.
Examples:
key may be any expression.
e must be a nonatomic expression,
and every argument of e must have exactly two parts.
assoc returns the second part of the first matching argument of e.
(%i1) assoc (f(x), foo(g(x) = y, f(x) = z + 1, h(x) = 2*u)); (%o1) z + 1
If there are two or more matches, only the first is returned.
(%i1) assoc (yy, [xx = 111, yy = 222, yy = 333, yy = 444]); (%o1) 222
If there are no matches, default is returned, if specified.
Otherwise, false is returned.
(%i1) assoc (abc, [[x, 111], [y, 222], [z, 333]], none); (%o1) none (%i2) assoc (abc, [[x, 111], [y, 222], [z, 333]]); (%o2) false
cons (expr, list) returns a new list constructed of the element
expr as its first element, followed by the elements of list. This is
analogous to the Lisp language construction operation "cons".
The Maxima function cons can also be used where the second argument is other
than a list and this might be useful. In this case, cons (expr_1, expr_2)
returns an expression with same operator as expr_2 but with argument cons(expr_1, args(expr_2)).
Examples:
(%i1) cons(a,[b,c,d]); (%o1) [a, b, c, d]
(%i2) cons(a,f(b,c,d)); (%o2) f(a, b, c, d)
In general, cons applied to a nonlist doesn’t make sense. For instance, cons(a,b^c)
results in an illegal expression, since ’^’ cannot take three arguments.
When inflag is true, cons operates on the internal structure of an expression, otherwise
cons operates on the displayed form. Especially when inflag is true, cons applied
to a nonlist sometimes gives a surprising result; for example
(%i1) cons(a,-a), inflag : true;
2
(%o1) - a
(%i2) cons(a,-a), inflag : false; (%o2) 0
Create a list by evaluating form with x_1 bound to each element of list_1, and for each such binding bind x_2 to each element of list_2, … The number of elements in the result will be the product of the number of elements in each list. Each variable x_i must actually be a symbol – it will not be evaluated. The list arguments will be evaluated once at the beginning of the iteration.
(%i1) create_list (x^i, i, [1, 3, 7]);
3 7
(%o1) [x, x , x ]
With a double iteration:
(%i1) create_list ([i, j], i, [a, b], j, [e, f, h]); (%o1) [[a, e], [a, f], [a, h], [b, e], [b, f], [b, h]]
Instead of list_i two args may be supplied each of which should evaluate to a number. These will be the inclusive lower and upper bounds for the iteration.
(%i1) create_list ([i, j], i, [1, 2, 3], j, 1, i); (%o1) [[1, 1], [2, 1], [2, 2], [3, 1], [3, 2], [3, 3]]
Note that the limits or list for the j variable can
depend on the current value of i.
delete(expr_1, expr_2)
removes from expr_2 any arguments of its top-level operator
which are the same (as determined by "=") as expr_1.
Note that "=" tests for formal equality, not equivalence.
Note also that arguments of subexpressions are not affected.
expr_1 may be an atom or a non-atomic expression.
expr_2 may be any non-atomic expression.
delete returns a new expression;
it does not modify expr_2.
delete(expr_1, expr_2, n)
removes from expr_2 the first n arguments of the top-level operator
which are the same as expr_1.
If there are fewer than n such arguments,
then all such arguments are removed.
Examples:
Removing elements from a list.
(%i1) delete (y, [w, x, y, z, z, y, x, w]); (%o1) [w, x, z, z, x, w]
Removing terms from a sum.
(%i1) delete (sin(x), x + sin(x) + y); (%o1) y + x
Removing factors from a product.
(%i1) delete (u - x, (u - w)*(u - x)*(u - y)*(u - z)); (%o1) (u - w) (u - y) (u - z)
Removing arguments from an arbitrary expression.
(%i1) delete (a, foo (a, b, c, d, a)); (%o1) foo(b, c, d)
Limit the number of removed arguments.
(%i1) delete (a, foo (a, b, a, c, d, a), 2); (%o1) foo(b, c, d, a)
Whether arguments are the same as expr_1 is determined by "=".
Arguments which are equal but not "=" are not removed.
(%i1) [is (equal (0, 0)), is (equal (0, 0.0)), is (equal (0, 0b0))]; (%o1) [true, true, true]
(%i2) [is (0 = 0), is (0 = 0.0), is (0 = 0b0)]; (%o2) [true, false, false]
(%i3) delete (0, [0, 0.0, 0b0]); (%o3) [0.0, 0.0b0]
(%i4) is (equal ((x + y)*(x - y), x^2 - y^2)); (%o4) true
(%i5) is ((x + y)*(x - y) = x^2 - y^2); (%o5) false
(%i6) delete ((x + y)*(x - y), [(x + y)*(x - y), x^2 - y^2]);
2 2
(%o6) [x - y ]
Returns the 8th item of expression or list expr.
See first for more details.
endcons (expr, list) returns a new list constructed of the elements of
list followed by expr. The Maxima function endcons can also be used where
the second argument is other than a list and this might be useful. In this case,
endcons (expr_1, expr_2) returns an expression with same operator as
expr_2 but with argument endcons(expr_1, args(expr_2)). Examples:
(%i1) endcons(a,[b,c,d]); (%o1) [b, c, d, a]
(%i2) endcons(a,f(b,c,d)); (%o2) f(b, c, d, a)
In general, endcons applied to a nonlist doesn’t make sense. For instance, endcons(a,b^c)
results in an illegal expression, since ’^’ cannot take three arguments.
When inflag is true, endcons operates on the internal structure of an expression, otherwise
endcons operates on the displayed form. Especially when inflag is true, endcons applied
to a nonlist sometimes gives a surprising result; for example
(%i1) endcons(a,-a), inflag : true;
2
(%o1) - a
(%i2) endcons(a,-a), inflag : false; (%o2) 0
Returns the 5th item of expression or list expr.
See first for more details.
Returns the first part of expr which may result in the first element of a list, the first row of a matrix, the first term of a sum, etc.:
(%i1) matrix([1,2],[3,4]);
[ 1 2 ]
(%o1) [ ]
[ 3 4 ]
(%i2) first(%);
(%o2) [1,2]
(%i3) first(%);
(%o3) 1
(%i4) first(a*b/c+d+e/x);
a b
(%o4) ---
c
(%i5) first(a=b/c+d+e/x);
(%o5) a
Note that
first and its related functions, rest and last, work
on the form of expr which is displayed not the form which is typed on
input. If the variable inflag is set to true however, these
functions will look at the internal form of expr. One reason why this may
make a difference is that the simplifier re-orders expressions:
(%i1) x+y; (%o1) y+1 (%i2) first(x+y),inflag : true; (%o2) x (%i3) first(x+y),inflag : false; (%o3) y
The functions second …
tenth yield the second through the tenth part of their input argument.
Returns the first count arguments of expr, if expr has at least count arguments. Returns expr if expr has less than count arguments.
expr may be any nonatomic expression.
When expr is something other than a list,
firstn returns an expression which has the same operator as expr.
count must be a nonnegative integer.
firstn honors the global flag inflag,
which governs whether the internal form of an expression is processed (when inflag is true)
or the displayed form (when inflag is false).
Note that firstn(expr, 1),
which returns a nonatomic expression containing the first argument,
is not the same as first(expr),
which returns the first argument by itself.
Examples:
firstn returns the first count elements of expr, if expr has at least count elements.
(%i1) mylist : [1, a, 2, b, 3, x, 4 - y, 2*z + sin(u)]; (%o1) [1, a, 2, b, 3, x, 4 - y, 2 z + sin(u)]
(%i2) firstn (mylist, 0); (%o2) []
(%i3) firstn (mylist, 1); (%o3) [1]
(%i4) firstn (mylist, 2); (%o4) [1, a]
(%i5) firstn (mylist, 7); (%o5) [1, a, 2, b, 3, x, 4 - y]
firstn returns expr if expr has less than count elements.
(%i1) mylist : [1, a, 2, b, 3, x, 4 - y, 2*z + sin(u)]; (%o1) [1, a, 2, b, 3, x, 4 - y, 2 z + sin(u)]
(%i2) firstn (mylist, 100); (%o2) [1, a, 2, b, 3, x, 4 - y, 2 z + sin(u)]
expr may be any nonatomic expression.
(%i1) myfoo : foo(1, a, 2, b, 3, x, 4 - y, 2*z + sin(u)); (%o1) foo(1, a, 2, b, 3, x, 4 - y, 2 z + sin(u))
(%i2) firstn (myfoo, 4); (%o2) foo(1, a, 2, b)
(%i3) mybar : bar[m, n](1, a, 2, b, 3, x, 4 - y, 2*z + sin(u));
(%o3) bar (1, a, 2, b, 3, x, 4 - y, 2 z + sin(u))
m, n
(%i4) firstn (mybar, 4);
(%o4) bar (1, a, 2, b)
m, n
(%i5) mymatrix : genmatrix (lambda ([i, j], 10*i + j), 10, 4) $
(%i6) firstn (mymatrix, 3);
[ 11 12 13 14 ]
[ ]
(%o6) [ 21 22 23 24 ]
[ ]
[ 31 32 33 34 ]
firstn honors the global flag inflag.
(%i1) myexpr : a + b + c + d + e; (%o1) e + d + c + b + a
(%i2) firstn (myexpr, 3), inflag=true; (%o2) c + b + a
(%i3) firstn (myexpr, 3), inflag=false; (%o3) e + d + c
Note that firstn(expr, 1) is not the same as first(expr).
(%i1) firstn ([w, x, y, z], 1); (%o1) [w]
(%i2) first ([w, x, y, z]); (%o2) w
Returns the 4th item of expression or list expr.
See first for more details.
Creates a new list containing the elements of lists l and m,
interspersed. The result has elements [l[1], m[1],
l[2], m[2], ...]. The lists l and m may contain any
type of elements.
If the lists are different lengths, join ignores elements of the longer
list.
Maxima complains if l or m is not a list.
See also append.
Examples:
(%i1) L1: [a, sin(b), c!, d - 1]; (%o1) [a, sin(b), c!, d - 1]
(%i2) join (L1, [1, 2, 3, 4]); (%o2) [a, 1, sin(b), 2, c!, 3, d - 1, 4]
(%i3) join (L1, [aa, bb, cc, dd, ee, ff]); (%o3) [a, aa, sin(b), bb, c!, cc, d - 1, dd]
Returns the last part (term, row, element, etc.) of the expr.
See also lastn.
Returns the last count arguments of expr, if expr has at least count arguments. Returns expr if expr has less than count arguments.
expr may be any nonatomic expression.
When expr is something other than a list,
lastn returns an expression which has the same operator as expr.
count must be a nonnegative integer.
lastn honors the global flag inflag,
which governs whether the internal form of an expression is processed (when inflag is true)
or the displayed form (when inflag is false).
Note that lastn(expr, 1),
which returns a nonatomic expression containing the last argument,
is not the same as last(expr),
which returns the last argument by itself.
Examples:
lastn returns the last count elements of expr, if expr has at least count elements.
(%i1) mylist : [1, a, 2, b, 3, x, 4 - y, 2*z + sin(u)]; (%o1) [1, a, 2, b, 3, x, 4 - y, 2 z + sin(u)]
(%i2) lastn (mylist, 0); (%o2) []
(%i3) lastn (mylist, 1); (%o3) [2 z + sin(u)]
(%i4) lastn (mylist, 2); (%o4) [4 - y, 2 z + sin(u)]
(%i5) lastn (mylist, 7); (%o5) [a, 2, b, 3, x, 4 - y, 2 z + sin(u)]
lastn returns expr if expr has less than count elements.
(%i1) mylist : [1, a, 2, b, 3, x, 4 - y, 2*z + sin(u)]; (%o1) [1, a, 2, b, 3, x, 4 - y, 2 z + sin(u)]
(%i2) lastn (mylist, 100); (%o2) [1, a, 2, b, 3, x, 4 - y, 2 z + sin(u)]
expr may be any nonatomic expression.
(%i1) myfoo : foo(1, a, 2, b, 3, x, 4 - y, 2*z + sin(u)); (%o1) foo(1, a, 2, b, 3, x, 4 - y, 2 z + sin(u))
(%i2) lastn (myfoo, 4); (%o2) foo(3, x, 4 - y, 2 z + sin(u))
(%i3) mybar : bar[m, n](1, a, 2, b, 3, x, 4 - y, 2*z + sin(u));
(%o3) bar (1, a, 2, b, 3, x, 4 - y, 2 z + sin(u))
m, n
(%i4) lastn (mybar, 4);
(%o4) bar (3, x, 4 - y, 2 z + sin(u))
m, n
(%i5) mymatrix : genmatrix (lambda ([i, j], 10*i + j), 10, 4) $
(%i6) lastn (mymatrix, 3);
[ 81 82 83 84 ]
[ ]
(%o6) [ 91 92 93 94 ]
[ ]
[ 101 102 103 104 ]
lastn honors the global flag inflag.
(%i1) myexpr : a + b + c + d + e; (%o1) e + d + c + b + a
(%i2) lastn (myexpr, 3), inflag=true; (%o2) e + d + c
(%i3) lastn (myexpr, 3), inflag=false; (%o3) c + b + a
Note that lastn(expr, 1) is not the same as last(expr).
(%i1) lastn ([w, x, y, z], 1); (%o1) [z]
(%i2) last ([w, x, y, z]); (%o2) z
Returns (by default) the number of parts in the external
(displayed) form of expr. For lists this is the number of elements,
for matrices it is the number of rows, and for sums it is the number
of terms (see dispform).
The length command is affected by the inflag switch. So, e.g.
length(a/(b*c)); gives 2 if inflag is false (Assuming
exptdispflag is true), but 3 if inflag is true (the
internal representation is essentially a*b^-1*c^-1).
Determining a list’s length typically needs an amount of time proportional to the number of elements in the list. If the length of a list is used inside a loop it therefore might drastically increase the performance if the length is calculated outside the loop instead.
Default value: true
If false causes any arithmetic operations with lists to be suppressed;
when true, list-matrix operations are contagious causing lists to be
converted to matrices yielding a result which is always a matrix. However,
list-list operations should return lists.
Returns true if expr is a list else false.
Extends the binary function F to an n-ary function by composition, where s is a list.
lreduce(F, s) returns F(... F(F(s_1, s_2), s_3), ... s_n).
When the optional argument s_0 is present,
the result is equivalent to lreduce(F, cons(s_0, s)).
The function F is first applied to the leftmost list elements, thus the name "lreduce".
See also rreduce, xreduce, and tree_reduce.
Examples:
lreduce without the optional argument.
(%i1) lreduce (f, [1, 2, 3]); (%o1) f(f(1, 2), 3)
(%i2) lreduce (f, [1, 2, 3, 4]); (%o2) f(f(f(1, 2), 3), 4)
lreduce with the optional argument.
(%i1) lreduce (f, [1, 2, 3], 4); (%o1) f(f(f(4, 1), 2), 3)
lreduce applied to built-in binary operators.
/ is the division operator.
(%i1) lreduce ("^", args ({a, b, c, d}));
b c d
(%o1) ((a ) )
(%i2) lreduce ("/", args ({a, b, c, d}));
a
(%o2) -----
b c d
The first form, makelist (), creates an empty list. The second form,
makelist (expr), creates a list with expr as its single
element. makelist (expr, n) creates a list of n
elements generated from expr.
The most general form, makelist (expr, i, i_0,
i_max, step), returns the list of elements obtained when
ev (expr, i=j) is applied to the elements
j of the sequence: i_0, i_0 + step, i_0 +
2*step, ..., with |j| less than or equal to |i_max|.
The increment step can be a number (positive or negative) or an expression. If it is omitted, the default value 1 will be used. If both i_0 and step are omitted, they will both have a default value of 1.
makelist (expr, x, list) returns a list, the
jth element of which is equal to
ev (expr, x=list[j]) for j equal to 1 through
length (list).
Examples:
(%i1) makelist (concat (x,i), i, 6); (%o1) [x1, x2, x3, x4, x5, x6]
(%i2) makelist (x=y, y, [a, b, c]); (%o2) [x = a, x = b, x = c]
(%i3) makelist (x^2, x, 3, 2*%pi, 2); (%o3) [9, 25]
(%i4) makelist (random(6), 4); (%o4) [2, 0, 2, 5]
(%i5) flatten (makelist (makelist (i^2, 3), i, 4)); (%o5) [1, 1, 1, 4, 4, 4, 9, 9, 9, 16, 16, 16]
(%i6) flatten (makelist (makelist (i^2, i, 3), 4)); (%o6) [1, 4, 9, 1, 4, 9, 1, 4, 9, 1, 4, 9]
Returns true if is(expr_1 = a)
for some element a in args(expr_2),
otherwise returns false.
expr_2 is typically a list, in which case
args(expr_2) = expr_2 and is(expr_1 = a)
for some element a in expr_2 is the test.
member does not inspect parts of the arguments of expr_2, so it
may return false even if expr_1 is a part of some argument of
expr_2.
See also elementp.
Examples:
(%i1) member (8, [8, 8.0, 8b0]); (%o1) true
(%i2) member (8, [8.0, 8b0]); (%o2) false
(%i3) member (b, [a, b, c]); (%o3) true
(%i4) member (b, [[a, b], [b, c]]); (%o4) false
(%i5) member ([b, c], [[a, b], [b, c]]); (%o5) true
(%i6) F (1, 1/2, 1/4, 1/8);
1 1 1
(%o6) F(1, -, -, -)
2 4 8
(%i7) member (1/8, %); (%o7) true
(%i8) member ("ab", ["aa", "ab", sin(1), a + b]);
(%o8) true
Returns the 9th item of expression or list expr.
See first for more details.
pop removes and returns the first element from the list list. The argument
list must be a mapatom that is bound to a nonempty list. If the argument list is
not bound to a nonempty list, Maxima signals an error. For examples, see push.
push prepends the item item to the list list and returns a copy of the new list.
The second argument list must be a mapatom that is bound to a list. The first argument item
can be any Maxima symbol or expression. If the argument list is not bound to a list, Maxima
signals an error.
To remove the first item from a list, see pop.
Examples:
(%i1) ll: []; (%o1) []
(%i2) push (x, ll); (%o2) [x]
(%i3) push (x^2+y, ll);
2
(%o3) [y + x , x]
(%i4) a: push ("string", ll);
2
(%o4) [string, y + x , x]
(%i5) pop (ll); (%o5) string
(%i6) pop (ll);
2
(%o6) y + x
(%i7) pop (ll); (%o7) x
(%i8) ll; (%o8) []
(%i9) a;
2
(%o9) [string, y + x , x]
Returns expr with its first n elements removed if n
is positive and its last - n elements removed if n
is negative. If n is 1 it may be omitted. The first argument
expr may be a list, matrix, or other expression. When expr
is an atom, rest signals an error; when expr is an empty
list and partswitch is false, rest signals an error. When
expr is an empty list and partswitch is true, rest
returns end.
Applying rest to expression such as f(a,b,c) returns
f(b,c). In general, applying rest to a nonlist doesn’t
make sense. For example, because ’^’ requires two arguments,
rest(a^b) results in an error message. The functions
args and op may be useful as well, since args(a^b)
returns [a,b] and op(a^b) returns ^.
(%i1) rest(a+b+c); (%o1) b+a (%i2) rest(a+b+c,2); (%o2) a (%i3) rest(a+b+c,-2); (%o3) c
Reverses the order of the members of the list (not
the members themselves). reverse also works on general expressions,
e.g. reverse(a=b); gives b=a.
See also sreverse.
Extends the binary function F to an n-ary function by composition, where s is a list.
rreduce(F, s) returns F(s_1, ... F(s_{n - 2}, F(s_{n - 1}, s_n))).
When the optional argument s_{n + 1} is present,
the result is equivalent to rreduce(F, endcons(s_{n + 1}, s)).
The function F is first applied to the rightmost list elements, thus the name "rreduce".
See also lreduce, tree_reduce, and xreduce.
Examples:
rreduce without the optional argument.
(%i1) rreduce (f, [1, 2, 3]); (%o1) f(1, f(2, 3))
(%i2) rreduce (f, [1, 2, 3, 4]); (%o2) f(1, f(2, f(3, 4)))
rreduce with the optional argument.
(%i1) rreduce (f, [1, 2, 3], 4); (%o1) f(1, f(2, f(3, 4)))
rreduce applied to built-in binary operators.
/ is the division operator.
(%i1) rreduce ("^", args ({a, b, c, d}));
d
c
b
(%o1) a
(%i2) rreduce ("/", args ({a, b, c, d}));
a c
(%o2) ---
b d
Returns the 2nd item of expression or list expr.
See first for more details.
Returns the 7th item of expression or list expr.
See first for more details.
Returns the 6th item of expression or list expr.
See first for more details.
sort(L, P) sorts a list L according to a predicate P of two arguments
which defines a strict weak order on the elements of L.
If P(a, b) is true, then a appears before b in the result.
If neither P(a, b) nor P(b, a) are true,
then a and b are equivalent, and appear in the result in the same order as in the input.
That is, sort is a stable sort.
If P(a, b) and P(b, a) are both true for some elements of L,
then P is not a valid sort predicate, and the result is undefined.
If P(a, b) is something other than true or false, sort signals an error.
The predicate may be specified as the name of a function
or binary infix operator, or as a lambda expression. If specified as
the name of an operator, the name must be enclosed in double quotes.
The sorted list is returned as a new object; the argument L is not modified.
sort(L) is equivalent to sort(L, orderlessp).
The default sorting order is ascending, as determined by orderlessp. The predicate ordergreatp sorts a list in descending order.
All Maxima atoms and expressions are comparable under orderlessp and ordergreatp.
Operators < and > order numbers, constants, and constant expressions by magnitude.
Note that orderlessp and ordergreatp do not order numbers, constants, and constant expressions by magnitude.
ordermagnitudep orders numbers, constants, and constant expressions the same as <,
and all other elements the same as orderlessp.
Examples:
sort sorts a list according to a predicate of two arguments
which defines a strict weak order on the elements of the list.
(%i1) sort ([1, a, b, 2, 3, c], 'orderlessp); (%o1) [1, 2, 3, a, b, c]
(%i2) sort ([1, a, b, 2, 3, c], 'ordergreatp); (%o2) [c, b, a, 3, 2, 1]
The predicate may be specified as the name of a function
or binary infix operator, or as a lambda expression. If specified as
the name of an operator, the name must be enclosed in double quotes.
(%i1) L : [[1, x], [3, y], [4, w], [2, z]]; (%o1) [[1, x], [3, y], [4, w], [2, z]]
(%i2) foo (a, b) := a[1] > b[1];
(%o2) foo(a, b) := a > b
1 1
(%i3) sort (L, 'foo); (%o3) [[4, w], [3, y], [2, z], [1, x]]
(%i4) infix (">>");
(%o4) >>
(%i5) a >> b := a[1] > b[1];
(%o5) (a >> b) := a > b
1 1
(%i6) sort (L, ">>"); (%o6) [[4, w], [3, y], [2, z], [1, x]]
(%i7) sort (L, lambda ([a, b], a[1] > b[1])); (%o7) [[4, w], [3, y], [2, z], [1, x]]
sort(L) is equivalent to sort(L, orderlessp).
(%i1) L : [a, 2*b, -5, 7, 1 + %e, %pi]; (%o1) [a, 2 b, - 5, 7, %e + 1, %pi]
(%i2) sort (L); (%o2) [- 5, 7, %e + 1, %pi, a, 2 b]
(%i3) sort (L, 'orderlessp); (%o3) [- 5, 7, %e + 1, %pi, a, 2 b]
The default sorting order is ascending, as determined by orderlessp. The predicate ordergreatp sorts a list in descending order.
(%i1) L : [a, 2*b, -5, 7, 1 + %e, %pi]; (%o1) [a, 2 b, - 5, 7, %e + 1, %pi]
(%i2) sort (L); (%o2) [- 5, 7, %e + 1, %pi, a, 2 b]
(%i3) sort (L, 'ordergreatp); (%o3) [2 b, a, %pi, %e + 1, 7, - 5]
All Maxima atoms and expressions are comparable under orderlessp and ordergreatp.
(%i1) L : [11, -17, 29b0, 9*c, 7.55, foo(x, y), -5/2, b + a];
5
(%o1) [11, - 17, 2.9b1, 9 c, 7.55, foo(x, y), - -, b + a]
2
(%i2) sort (L, orderlessp);
5
(%o2) [- 17, - -, 7.55, 11, 2.9b1, b + a, 9 c, foo(x, y)]
2
(%i3) sort (L, ordergreatp);
5
(%o3) [foo(x, y), 9 c, b + a, 2.9b1, 11, 7.55, - -, - 17]
2
Operators < and > order numbers, constants, and constant expressions by magnitude.
Note that orderlessp and ordergreatp do not order numbers, constants, and constant expressions by magnitude.
(%i1) L : [%pi, 3, 4, %e, %gamma]; (%o1) [%pi, 3, 4, %e, %gamma]
(%i2) sort (L, ">"); (%o2) [4, %pi, 3, %e, %gamma]
(%i3) sort (L, ordergreatp); (%o3) [%pi, %gamma, %e, 4, 3]
ordermagnitudep orders numbers, constants, and constant expressions the same as <,
and all other elements the same as orderlessp.
(%i1) L: [%i, 1+%i, 2*x, minf, inf, %e, sin(1), 0,1,2,3, 1.0, 1.0b0];
(%o1) [%i, %i + 1, 2 x, minf, inf, %e, sin(1), 0, 1, 2, 3, 1.0,
1.0b0]
(%i2) sort (L, ordermagnitudep);
(%o2) [minf, 0, sin(1), 1, 1.0, 1.0b0, 2, %e, 3, inf, %i,
%i + 1, 2 x]
(%i3) sort (L, orderlessp);
(%o3) [0, 1, 1.0, 2, 3, sin(1), 1.0b0, %e, %i, %i + 1, inf,
minf, 2 x]
Returns the list of elements of list for which the predicate p
returns true.
Example:
(%i1) L: [1, 2, 3, 4, 5, 6]; (%o1) [1, 2, 3, 4, 5, 6]
(%i2) sublist (L, evenp); (%o2) [2, 4, 6]
Returns the indices of the elements x of the list L for which
the predicate maybe(P(x)) returns true;
this excludes unknown as well as false.
P may be the name of a function or a lambda expression.
L must be a literal list.
Examples:
(%i1) sublist_indices ('[a, b, b, c, 1, 2, b, 3, b],
lambda ([x], x='b));
(%o1) [2, 3, 7, 9]
(%i2) sublist_indices ('[a, b, b, c, 1, 2, b, 3, b], symbolp);
(%o2) [1, 2, 3, 4, 7, 9]
(%i3) sublist_indices ([1 > 0, 1 < 0, 2 < 1, 2 > 1, 2 > 0],
identity);
(%o3) [1, 4, 5]
(%i4) assume (x < -1); (%o4) [x < - 1]
(%i5) map (maybe, [x > 0, x < 0, x < -2]); (%o5) [false, true, unknown]
(%i6) sublist_indices ([x > 0, x < 0, x < -2], identity); (%o6) [2]
Returns the 10th item of expression or list expr.
See first for more details.
Returns the 3rd item of expression or list expr.
See first for more details.
Extends the binary function F to an n-ary function by composition, where s is a set or list.
tree_reduce is equivalent to the following:
Apply F to successive pairs of elements
to form a new list [F(s_1, s_2), F(s_3, s_4), ...],
carrying the final element unchanged if there are an odd number of elements.
Then repeat until the list is reduced to a single element, which is the return value.
When the optional argument s_0 is present,
the result is equivalent tree_reduce(F, cons(s_0, s)).
For addition of floating point numbers,
tree_reduce may return a sum that has a smaller rounding error
than either rreduce or lreduce.
The elements of s and the partial results may be arranged in a minimum-depth binary tree, thus the name "tree_reduce".
Examples:
tree_reduce applied to a list with an even number of elements.
(%i1) tree_reduce (f, [a, b, c, d]); (%o1) f(f(a, b), f(c, d))
tree_reduce applied to a list with an odd number of elements.
(%i1) tree_reduce (f, [a, b, c, d, e]); (%o1) f(f(f(a, b), f(c, d)), e)
Returns the unique elements of the list L.
When all the elements of L are unique,
unique returns a shallow copy of L,
not L itself.
If L is not a list, unique returns L.
Example:
(%i1) unique ([1, %pi, a + b, 2, 1, %e, %pi, a + b, [1]]); (%o1) [1, 2, %e, %pi, [1], b + a]
Extends the function F to an n-ary function by composition,
or, if F is already n-ary, applies F to s.
When F is not n-ary, xreduce is the same as lreduce.
The argument s is a list.
Functions known to be n-ary include
addition +, multiplication *, and, or, max,
min, and append.
Functions may also be declared n-ary by declare(F, nary).
For these functions,
xreduce is expected to be faster than either rreduce or lreduce.
When the optional argument s_0 is present,
the result is equivalent to xreduce(s, cons(s_0, s)).
Floating point addition is not exactly associative; be that as it may,
xreduce applies Maxima’s n-ary addition when s contains floating point numbers.
Examples:
xreduce applied to a function known to be n-ary.
F is called once, with all arguments.
(%i1) declare (F, nary); (%o1) done
(%i2) F ([L]) := L; (%o2) F([L]) := L
(%i3) xreduce (F, [a, b, c, d, e]); (%o3) [a, b, c, d, e]
xreduce applied to a function not known to be n-ary.
G is called several times, with two arguments each time.
(%i1) G ([L]) := L; (%o1) G([L]) := L
(%i2) xreduce (G, [a, b, c, d, e]); (%o2) [[[[a, b], c], d], e]
(%i3) lreduce (G, [a, b, c, d, e]); (%o3) [[[[a, b], c], d], e]
Previous: Functions and Variables for Lists, Up: Lists [Contents][Index]
Lists provide efficient ways of appending and removing elements. They can be created without knowing their final dimensions. Lisp provides efficient means of copying and handling lists. Also nested lists do not need to be strictly rectangular. These advantages over declared arrays come with the drawback that the amount of time needed for accessing a random element within a list may be roughly proportional to the element’s distance from its beginning. Efficient traversal of lists is still possible, though, by using the list as a stack or a fifo:
(%i1) l:[Test,1,2,3,4]; (%o1) [Test, 1, 2, 3, 4]
(%i2) while l # [] do
disp(pop(l));
Test
1
2
3
4
(%o2) done
Another even faster example would be:
(%i1) l:[Test,1,2,3,4]; (%o1) [Test, 1, 2, 3, 4]
(%i2) for i in l do
disp(pop(l));
Test
1
2
3
4
(%o2) done
Beginning traversal with the last element of a list is possible after
reversing the list using reverse ().
If the elements of a long list need to be processed in a different
order performance might be increased by converting the list into a
declared array first.
Note also that the ending condition of for loops
is tested for every iteration which means that the result of a
length should be cached if it is used in the ending
condition:
(%i1) l:makelist(i,i,1,100000)$
(%i2) lngth:length(l); (%o2) 100000
(%i3) x:1; (%o3) 1
(%i4) for i:1 thru lngth do
x:x+1$
(%i5) x; (%o5) 100001
Next: Structures, Previous: Lists, Up: Data Types and Structures [Contents][Index]
Maxima supports 3 array-like constructs:
(%i1) a["feww"]:1; (%o1) 1
(%i2) a[qqwdqwd]:3; (%o2) 3
(%i3) a[5]:99; (%o3) 99
(%i4) a[qqwdqwd]; (%o4) 3
(%i5) a[5]; (%o5) 99
(%i6) a["feww"]; (%o6) 1
Since lisp handles hashed arrays and memoizing functions similar to arrays
many of the functions that can be applied to arrays can be applied to them, as well.
makelist allow for fast addition and removal
of elements, can be created without knowing their final size.
Creates an n-dimensional array. n may be less than or equal to 5. The subscripts for the i’th dimension are the integers running from 0 to dim_i.
array (name, dim_1, ..., dim_n) creates a general
array.
array (name, type, dim_1, ..., dim_n) creates
an array, with elements of a specified type. type can be fixnum
for integers of limited size or flonum for floating-point numbers.
array ([name_1, ..., name_m], dim_1, ..., dim_n)
creates m arrays, all of the same dimensions.
See also arraymake, arrayinfo and make_array.
Evaluates A [i_1, ..., i_n],
where A is an array and i_1, …, i_n are integers.
This is reminiscent of apply, except the first argument is an array
instead of a function.
Returns information about the array A.
The argument A may be a declared array, a hashed array,
a memoizing function, or a subscripted function.
For declared arrays, arrayinfo returns a list comprising the atom
declared, the number of dimensions, and the size of each dimension.
The elements of the array, both bound and unbound, are returned by
listarray.
For undeclared arrays (hashed arrays), arrayinfo returns a list
comprising the atom hashed, the number of subscripts,
and the subscripts of every element which has a value.
The values are returned by listarray.
For memoizing functions, arrayinfo returns a list comprising the atom
hashed, the number of subscripts,
and any subscript values for which there are stored function values.
The stored function values are returned by listarray.
For subscripted functions, arrayinfo returns a list comprising the atom
hashed, the number of subscripts,
and any subscript values for which there are lambda expressions.
The lambda expressions are returned by listarray.
See also listarray.
Examples:
arrayinfo and listarray applied to a declared array.
(%i1) array (aa, 2, 3); (%o1) aa
(%i2) aa [2, 3] : %pi; (%o2) %pi
(%i3) aa [1, 2] : %e; (%o3) %e
(%i4) arrayinfo (aa); (%o4) [declared, 2, [2, 3]]
(%i5) listarray (aa);
(%o5) [#####, #####, #####, #####, #####, #####, %e, #####,
#####, #####, #####, %pi]
arrayinfo and listarray applied to an undeclared array (hashed array.).
(%i1) bb [FOO] : (a + b)^2;
2
(%o1) (b + a)
(%i2) bb [BAR] : (c - d)^3;
3
(%o2) (c - d)
(%i3) arrayinfo (bb); (%o3) [hashed, 1, [BAR], [FOO]]
(%i4) listarray (bb);
3 2
(%o4) [(c - d) , (b + a) ]
arrayinfo and listarray applied to a memoizing function.
(%i1) cc [x, y] := y / x;
y
(%o1) cc := -
x, y x
(%i2) cc [u, v];
v
(%o2) -
u
(%i3) cc [4, z];
z
(%o3) -
4
(%i4) arrayinfo (cc); (%o4) [hashed, 2, [4, z], [u, v]]
(%i5) listarray (cc);
z v
(%o5) [-, -]
4 u
Using arrayinfo in order to convert an undeclared array to a declared array:
(%i1) for i:0 thru 10 do a[i]:i^2$
(%i2) indices:map(first,rest(rest(arrayinfo(a)))); (%o2) [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
(%i3) array(A,fixnum,length(indices)-1)$ (%i4) fillarray(A,map(lambda([x],a[x]),indices))$
(%i5) listarray(A); (%o5) [0, 1, 4, 9, 16, 25, 36, 49, 64, 81, 100]
arrayinfo and listarray applied to a subscripted function.
(%i1) dd [x] (y) := y ^ x;
x
(%o1) dd (y) := y
x
(%i2) dd [a + b];
b + a
(%o2) lambda([y], y )
(%i3) dd [v - u];
v - u
(%o3) lambda([y], y )
(%i4) arrayinfo (dd); (%o4) [hashed, 1, [b + a], [v - u]]
(%i5) listarray (dd);
b + a v - u
(%o5) [lambda([y], y ), lambda([y], y )]
Returns the expression A[i_1, ..., i_n].
The result is an unevaluated array reference.
arraymake is reminiscent of funmake, except the return value
is an unevaluated array reference instead of an unevaluated function call.
Examples:
(%i1) arraymake (A, [1]);
(%o1) A
1
(%i2) arraymake (A, [k]);
(%o2) A
k
(%i3) arraymake (A, [i, j, 3]);
(%o3) A
i, j, 3
(%i4) array (A, fixnum, 10); (%o4) A
(%i5) fillarray (A, makelist (i^2, i, 1, 11)); (%o5) A
(%i6) arraymake (A, [5]);
(%o6) A
5
(%i7) ''%; (%o7) 36
(%i8) L : [a, b, c, d, e]; (%o8) [a, b, c, d, e]
(%i9) arraymake ('L, [n]);
(%o9) L
n
(%i10) ''%, n = 3; (%o10) c
(%i11) A2 : make_array (fixnum, 10);
(%o11) {Lisp Array: #(0 0 0 0 0 0 0 0 0 0)}
(%i12) fillarray (A2, [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]);
(%o12) {Lisp Array: #(1 2 3 4 5 6 7 8 9 10)}
(%i13) arraymake ('A2, [8]);
(%o13) A2
8
(%i14) ''%; (%o14) 9
Default value: []
arrays is a list of arrays that have been allocated.
These comprise arrays declared by array, hashed arrays that can be
constructed by implicit definition (assigning something to an element that isn’t yet
declared as a list or an array),
and memoizing functions defined by := and define.
Arrays defined by make_array are not included.
See also
array, arrayapply, arrayinfo,
arraymake, fillarray, listarray, and
rearray.
Examples:
(%i1) array (aa, 5, 7); (%o1) aa
(%i2) bb [FOO] : (a + b)^2;
2
(%o2) (b + a)
(%i3) cc [x] := x/100;
x
(%o3) cc := ---
x 100
(%i4) dd : make_array ('any, 7);
(%o4) {Lisp Array: #(NIL NIL NIL NIL NIL NIL NIL)}
(%i5) arrays; (%o5) [aa, bb, cc]
Assigns x to A[i_1, ..., i_n],
where A is an array and i_1, …, i_n are integers.
arraysetapply evaluates its arguments.
Fills array A from B, which is a list or an array.
If a specific type was declared for A when it was created, it can only be filled with elements of that same type; it is an error if an attempt is made to copy an element of a different type.
If the dimensions of the arrays A and B are different, A is filled in row-major order. If there are not enough elements in B the last element is used to fill out the rest of A. If there are too many, the remaining ones are ignored.
fillarray returns its first argument.
Examples:
Create an array of 9 elements and fill it from a list.
(%i1) array (a1, fixnum, 8); (%o1) a1
(%i2) listarray (a1); (%o2) [0, 0, 0, 0, 0, 0, 0, 0, 0]
(%i3) fillarray (a1, [1, 2, 3, 4, 5, 6, 7, 8, 9]); (%o3) a1
(%i4) listarray (a1); (%o4) [1, 2, 3, 4, 5, 6, 7, 8, 9]
When there are too few elements to fill the array, the last element is repeated. When there are too many elements, the extra elements are ignored.
(%i1) a2 : make_array (fixnum, 8);
(%o1) {Lisp Array: #(0 0 0 0 0 0 0 0)}
(%i2) fillarray (a2, [1, 2, 3, 4, 5]);
(%o2) {Lisp Array: #(1 2 3 4 5 5 5 5)}
(%i3) fillarray (a2, [4]);
(%o3) {Lisp Array: #(4 4 4 4 4 4 4 4)}
(%i4) fillarray (a2, makelist (i, i, 1, 100));
(%o4) {Lisp Array: #(1 2 3 4 5 6 7 8)}
Multiple-dimension arrays are filled in row-major order.
(%i1) a3 : make_array (fixnum, 2, 5);
(%o1) {Lisp Array: #2A((0 0 0 0 0) (0 0 0 0 0))}
(%i2) fillarray (a3, [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]);
(%o2) {Lisp Array: #2A((1 2 3 4 5) (6 7 8 9 10))}
(%i3) a4 : make_array (fixnum, 5, 2);
(%o3) {Lisp Array: #2A((0 0) (0 0) (0 0) (0 0) (0 0))}
(%i4) fillarray (a4, a3);
(%o4) {Lisp Array: #2A((1 2) (3 4) (5 6) (7 8) (9 10))}
Returns a list of the elements of the array A.
The argument A may be an array, an undeclared array (hashed array),
a memoizing function, or a subscripted function.
Elements are listed in row-major order.
That is, elements are sorted according to the first index, then according to
the second index, and so on. The sorting order of index values is the same as
the order established by orderless.
For undeclared arrays (hashed arrays), memoizing functions, and subscripted functions,
the elements correspond to the index values returned by arrayinfo.
Unbound elements of general arrays (that is, not fixnum and not
flonum) are returned as #####.
Unbound elements of fixnum or flonum arrays
are returned as 0 or 0.0, respectively.
Unbound elements of hashed arrays, memoizing functions,
and subscripted functions are not returned.
Examples:
listarray and arrayinfo applied to a declared array.
(%i1) array (aa, 2, 3); (%o1) aa
(%i2) aa [2, 3] : %pi; (%o2) %pi
(%i3) aa [1, 2] : %e; (%o3) %e
(%i4) listarray (aa);
(%o4) [#####, #####, #####, #####, #####, #####, %e, #####,
#####, #####, #####, %pi]
(%i5) arrayinfo (aa); (%o5) [declared, 2, [2, 3]]
listarray and arrayinfo applied to an undeclared array (hashed array).
(%i1) bb [FOO] : (a + b)^2;
2
(%o1) (b + a)
(%i2) bb [BAR] : (c - d)^3;
3
(%o2) (c - d)
(%i3) listarray (bb);
3 2
(%o3) [(c - d) , (b + a) ]
(%i4) arrayinfo (bb); (%o4) [hashed, 1, [BAR], [FOO]]
listarray and arrayinfo applied to a memoizing function.
(%i1) cc [x, y] := y / x;
y
(%o1) cc := -
x, y x
(%i2) cc [u, v];
v
(%o2) -
u
(%i3) cc [4, z];
z
(%o3) -
4
(%i4) listarray (cc);
z v
(%o4) [-, -]
4 u
(%i5) arrayinfo (cc); (%o5) [hashed, 2, [4, z], [u, v]]
listarray and arrayinfo applied to a subscripted function.
(%i1) dd [x] (y) := y ^ x;
x
(%o1) dd (y) := y
x
(%i2) dd [a + b];
b + a
(%o2) lambda([y], y )
(%i3) dd [v - u];
v - u
(%o3) lambda([y], y )
(%i4) listarray (dd);
b + a v - u
(%o4) [lambda([y], y ), lambda([y], y )]
(%i5) arrayinfo (dd); (%o5) [hashed, 1, [b + a], [v - u]]
Creates and returns a Lisp array. type may
be any, flonum, fixnum, hashed or
functional.
There are n indices,
and the i’th index runs from 0 to dim_i - 1.
The advantage of make_array over array is that the return value
doesn’t have a name, and once a pointer to it goes away, it will also go away.
For example, if y: make_array (...) then y points to an object
which takes up space, but after y: false, y no longer
points to that object, so the object can be garbage collected.
Examples:
(%i1) A1 : make_array (fixnum, 10);
(%o1) {Lisp Array: #(0 0 0 0 0 0 0 0 0 0)}
(%i2) A1 [8] : 1729; (%o2) 1729
(%i3) A1;
(%o3) {Lisp Array: #(0 0 0 0 0 0 0 0 1729 0)}
(%i4) A2 : make_array (flonum, 10);
(%o4) {Lisp Array: #(0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0)}
(%i5) A2 [2] : 2.718281828; (%o5) 2.718281828
(%i6) A2;
(%o6)
{Lisp Array: #(0.0 0.0 2.718281828 0.0 0.0 0.0 0.0 0.0 0.0 0.0)}
(%i7) A3 : make_array (any, 10);
(%o7) {Lisp Array: #(NIL NIL NIL NIL NIL NIL NIL NIL NIL NIL)}
(%i8) A3 [4] : x - y - z; (%o8) (- z) - y + x
(%i9) A3;
(%o9) {Lisp Array: #(NIL NIL NIL NIL
((MPLUS SIMP) $X ((MTIMES SIMP) -1 $Y) ((MTIMES S\
IMP) -1 $Z))
NIL NIL NIL NIL NIL)}
(%i10) A4 : make_array (fixnum, 2, 3, 5);
(%o10) {Lisp Array: #3A(((0 0 0 0 0) (0 0 0 0 0) (0 0 0 0 0))
((0 0 0 0 0) (0 0 0 0 0) (0 0 0 0 0)))}
(%i11) fillarray (A4, makelist (i, i, 1, 2*3*5));
(%o11) {Lisp Array: #3A(((1 2 3 4 5) (6 7 8 9 10) (11 12 13 14 1\
5))
((16 17 18 19 20) (21 22 23 24 25) (26 27 28 29\
30)))}
(%i12) A4 [0, 2, 1]; (%o12) 12
Changes the dimensions of an array.
The new array will be filled with the elements of the old one in
row-major order. If the old array was too small,
the remaining elements are filled with
false, 0.0 or 0,
depending on the type of the array. The type of the array cannot be
changed.
Removes arrays and array associated functions and frees the storage occupied.
The arguments may be declared arrays, hashed arrays, array
functions, and subscripted functions.
remarray (all) removes all items in the global list arrays.
It may be necessary to use this function if it is
desired to clear the cache of a memoizing function.
remarray returns the list of arrays removed.
remarray quotes its arguments.
Evaluates the subscripted expression x[i].
subvar evaluates its arguments.
arraymake (x, [i]) constructs the expression
x[i], but does not evaluate it.
Examples:
(%i1) x : foo $ (%i2) i : 3 $
(%i3) subvar (x, i);
(%o3) foo
3
(%i4) foo : [aa, bb, cc, dd, ee]$
(%i5) subvar (x, i); (%o5) cc
(%i6) arraymake (x, [i]);
(%o6) foo
3
(%i7) ''%; (%o7) cc
Returns true if expr is a subscripted variable, for example
a[i].
Default value: false
When use_fast_arrays is true,
arrays declared by array are values instead of properties,
and undeclared arrays (hashed arrays) are implemented as Lisp hashed arrays.
When use_fast_arrays is false,
arrays declared by array are properties,
and undeclared arrays are implemented with Maxima’s own hashed array implementation.
Note that the code use_fast_arrays switches to is not necessarily faster
than the default one; Arrays created by make_array are not affected by
use_fast_arrays.
See also translate_fast_arrays.
Default value: false
When translate_fast_arrays is true,
the Maxima-to-Lisp translator generates code that assumes arrays are values instead of properties,
as if use_fast_arrays were true.
When translate_fast_arrays is false,
the Maxima-to-Lisp translator generates code that assumes arrays are properties,
as if use_fast_arrays were false.
Previous: Arrays, Up: Data Types and Structures [Contents][Index]
Next: Functions and Variables for Structures, Previous: Structures, Up: Structures [Contents][Index]
Maxima provides a simple data aggregate called a structure. A structure is an expression in which arguments are identified by name (the field name) and the expression as a whole is identified by its operator (the structure name). A field value can be any expression.
A structure is defined by the defstruct function;
the global variable structures is the list of user-defined structures.
The function new creates instances of structures.
The @ operator refers to fields.
kill(S) removes the structure definition S,
and kill(x@ a) unbinds the field a of the structure instance x.
In the pretty-printing console display (with display2d equal to true),
structure instances are displayed with the value of each field
represented as an equation, with the field name on the left-hand side
and the value on the right-hand side.
(The equation is only a display construct; only the value is actually stored.)
In 1-dimensional display (via grind or with display2d equal to false),
structure instances are displayed without the field names.
There is no way to use a field name as a function name, although a field value can be a lambda expression. Nor can the values of fields be restricted to certain types; any field can be assigned any kind of expression. There is no way to make some fields accessible or inaccessible in different contexts; all fields are always visible.
Previous: Introduction to Structures, Up: Structures [Contents][Index]
structures is the list of user-defined structures defined by defstruct.
Define a structure, which is a list of named fields a_1, …,
a_n associated with a symbol S.
An instance of a structure is just an expression which has operator S
and exactly n arguments.
new(S) creates a new instance of structure S.
An argument which is just a symbol a specifies the name of a field.
An argument which is an equation a = v specifies the field name a
and its default value v.
The default value can be any expression.
defstruct puts S on the list of user-defined structures, structures.
kill(S) removes S from the list of user-defined structures,
and removes the structure definition.
Examples:
(%i1) defstruct (foo (a, b, c)); (%o1) [foo(a, b, c)] (%i2) structures; (%o2) [foo(a, b, c)] (%i3) new (foo); (%o3) foo(a, b, c) (%i4) defstruct (bar (v, w, x = 123, y = %pi)); (%o4) [bar(v, w, x = 123, y = %pi)] (%i5) structures; (%o5) [foo(a, b, c), bar(v, w, x = 123, y = %pi)] (%i6) new (bar); (%o6) bar(v, w, x = 123, y = %pi) (%i7) kill (foo); (%o7) done (%i8) structures; (%o8) [bar(v, w, x = 123, y = %pi)]
new creates new instances of structures.
new(S) creates a new instance of structure S
in which each field is assigned its default value, if any,
or no value at all if no default was specified in the structure definition.
new(S(v_1, ..., v_n)) creates a new instance of S
in which fields are assigned the values v_1, …, v_n.
Examples:
(%i1) defstruct (foo (w, x = %e, y = 42, z)); (%o1) [foo(w, x = %e, y = 42, z)] (%i2) new (foo); (%o2) foo(w, x = %e, y = 42, z) (%i3) new (foo (1, 2, 4, 8)); (%o3) foo(w = 1, x = 2, y = 4, z = 8)
@ is the structure field access operator.
The expression x@ a refers to the value of field a of the structure instance x.
The field name is not evaluated.
If the field a in x has not been assigned a value,
x@ a evaluates to itself.
kill(x@ a) removes the value of field a in x.
Examples:
(%i1) defstruct (foo (x, y, z)); (%o1) [foo(x, y, z)] (%i2) u : new (foo (123, a - b, %pi)); (%o2) foo(x = 123, y = a - b, z = %pi) (%i3) u@z; (%o3) %pi (%i4) u@z : %e; (%o4) %e (%i5) u; (%o5) foo(x = 123, y = a - b, z = %e) (%i6) kill (u@z); (%o6) done (%i7) u; (%o7) foo(x = 123, y = a - b, z) (%i8) u@z; (%o8) u@z
The field name is not evaluated.
(%i1) defstruct (bar (g, h)); (%o1) [bar(g, h)] (%i2) x : new (bar); (%o2) bar(g, h) (%i3) x@h : 42; (%o3) 42 (%i4) h : 123; (%o4) 123 (%i5) x@h; (%o5) 42 (%i6) x@h : 19; (%o6) 19 (%i7) x; (%o7) bar(g, h = 19) (%i8) h; (%o8) 123
Next: Expressions, Previous: Command Line [Contents][Index]