Next: Characters, Previous: Introduction to String Processing, Up: stringproc [Contents][Index]
Example: Formatted printing to a file.
(%i1) s: openw("file.txt");
(%o1) #<output stream file.txt>
(%i2) control:
"~2tAn atom: ~20t~a~%~2tand a list: ~20t~{~r ~}~%~2t\
and an integer: ~20t~d~%"$
(%i3) printf( s,control, 'true,[1,2,3],42 )$
(%o3) false
(%i4) close(s);
(%o4) true
(%i5) s: openr("file.txt");
(%o5) #<input stream file.txt>
(%i6) while stringp( tmp:readline(s) ) do print(tmp)$
An atom: true
and a list: one two three
and an integer: 42
(%i7) close(s)$
Closes stream and returns true if stream had been open.
stream has to be an open stream from or to a file.
flength then returns the number of bytes which are currently present in this file.
Example: See writebyte .
Flushes stream where stream has to be an output stream to a file.
Example: See writebyte .
Returns the current position in stream, if pos is not used.
If pos is used, fposition sets the position in stream.
stream has to be a stream from or to a file and
pos has to be a positive number.
Positions in data streams are like in strings or lists 1-indexed, i.e. the first element in stream is in position 1.
Writes a new line to the standard output stream
if the position is not at the beginning of a line and returns true.
Using the optional argument stream the new line is written to that stream.
There are some cases, where freshline() does not work as expected.
See also newline.
Returns a string containing all the characters currently present in stream which must be an open string-output stream. The returned characters are removed from stream.
Example: See make_string_output_stream .
Returns an input stream which contains parts of string and an end of file. Without optional arguments the stream contains the entire string and is positioned in front of the first character. start and end define the substring contained in the stream. The first character is available at position 1.
(%i1) istream : make_string_input_stream("text", 1, 4);
(%o1) #<string-input stream from "text">
(%i2) (while (c : readchar(istream)) # false do sprint(c), newline())$
t e x
(%i3) close(istream)$
Returns an output stream that accepts characters. Characters currently present in this stream can be retrieved by get_output_stream_string.
(%i1) ostream : make_string_output_stream(); (%o1) #<string-output stream 09622ea0> (%i2) printf(ostream, "foo")$ (%i3) printf(ostream, "bar")$ (%i4) string : get_output_stream_string(ostream); (%o4) foobar (%i5) printf(ostream, "baz")$ (%i6) string : get_output_stream_string(ostream); (%o6) baz (%i7) close(ostream)$
Writes a new line to the standard output stream.
Using the optional argument stream the new line is written to that stream.
There are some cases, where newline() does not work as expected.
See sprint for an example of using newline().
Returns a character output stream to file.
If an existing file is opened, opena appends elements at the end of file.
For binary output see opena_binary .
Returns a character input stream to file.
openr assumes that file already exists.
If reading the file results in a lisp error about its encoding
passing the correct string as the argument encoding might help.
The available encodings and their names depend on the lisp being used.
For sbcl a list of suitable strings can be found at
http://www.sbcl.org/manual/#External-Formats.
For binary input see openr_binary .
See also close and openw.
(%i1) istream : openr("data.txt","EUC-JP");
(%o1) #<FD-STREAM for "file /home/gunter/data.txt" {10099A3AE3}>
(%i2) close(istream);
(%o2) true
Returns a character output stream to file.
If file does not exist, it will be created.
If an existing file is opened, openw destructively modifies file.
For binary output see openw_binary .
Produces formatted output by outputting the characters of control-string string and observing that a tilde introduces a directive. The character after the tilde, possibly preceded by prefix parameters and modifiers, specifies what kind of formatting is desired. Most directives use one or more elements of the arguments expr_1, ..., expr_n to create their output.
If dest is a stream or true, then printf returns false.
Otherwise, printf returns a string containing the output.
By default the streams stdin, stdout and stderr are defined.
If Maxima is running as a network client (which is the normal case if Maxima is communicating
with a graphical user interface, which must be the server) setup-client
will define old_stdout and old_stderr, too.
printf provides the Common Lisp function format in Maxima.
The following example illustrates the general relation between these two
functions.
(%i1) printf(true, "R~dD~d~%", 2, 2); R2D2 (%o1) false (%i2) :lisp (format t "R~dD~d~%" 2 2) R2D2 NIL
The following description is limited to a rough sketch of the possibilities of
printf.
The Lisp function format is described in detail in many reference books.
Of good help is e.g. the free available online-manual
"Common Lisp the Language" by Guy L. Steele. See chapter 22.3.3 there.
In addition, printf recognizes two format directives which are not known to Lisp format.
The format directive ~m indicates Maxima pretty printer output.
The format directive ~h indicates a bigfloat number.
~% new line
~& fresh line
~t tab
~$ monetary
~d decimal integer
~b binary integer
~o octal integer
~x hexadecimal integer
~br base-b integer
~r spell an integer
~p plural
~f floating point
~e scientific notation
~g ~f or ~e, depending upon magnitude
~h bigfloat
~a uses Maxima function string
~m Maxima pretty printer output
~s like ~a, but output enclosed in "double quotes"
~~ ~
~< justification, ~> terminates
~( case conversion, ~) terminates
~[ selection, ~] terminates
~{ iteration, ~} terminates
Note that the directive ~* is not supported.
If dest is a stream or true, then printf returns false.
Otherwise, printf returns a string containing the output.
(%i1) printf( false, "~a ~a ~4f ~a ~@r",
"String",sym,bound,sqrt(12),144), bound = 1.234;
(%o1) String sym 1.23 2*sqrt(3) CXLIV
(%i2) printf( false,"~{~a ~}",["one",2,"THREE"] );
(%o2) one 2 THREE
(%i3) printf(true,"~{~{~9,1f ~}~%~}",mat ),
mat = args(matrix([1.1,2,3.33],[4,5,6],[7,8.88,9]))$
1.1 2.0 3.3
4.0 5.0 6.0
7.0 8.9 9.0
(%i4) control: "~:(~r~) bird~p ~[is~;are~] singing."$
(%i5) printf( false,control, n,n,if n=1 then 1 else 2 ), n=2;
(%o5) Two birds are singing.
The directive ~h has been introduced to handle bigfloats.
~w,d,e,x,o,p@H w : width d : decimal digits behind floating point e : minimal exponent digits x : preferred exponent o : overflow character p : padding character @ : display sign for positive numbers
(%i1) fpprec : 1000$ (%i2) printf(true, "|~h|~%", 2.b0^-64)$ |0.0000000000000000000542101086242752217003726400434970855712890625| (%i3) fpprec : 26$ (%i4) printf(true, "|~h|~%", sqrt(2))$ |1.4142135623730950488016887| (%i5) fpprec : 24$ (%i6) printf(true, "|~h|~%", sqrt(2))$ |1.41421356237309504880169| (%i7) printf(true, "|~28h|~%", sqrt(2))$ | 1.41421356237309504880169| (%i8) printf(true, "|~28,,,,,'*h|~%", sqrt(2))$ |***1.41421356237309504880169| (%i9) printf(true, "|~,18h|~%", sqrt(2))$ |1.414213562373095049| (%i10) printf(true, "|~,,,-3h|~%", sqrt(2))$ |1414.21356237309504880169b-3| (%i11) printf(true, "|~,,2,-3h|~%", sqrt(2))$ |1414.21356237309504880169b-03| (%i12) printf(true, "|~20h|~%", sqrt(2))$ |1.41421356237309504880169| (%i13) printf(true, "|~20,,,,'+h|~%", sqrt(2))$ |++++++++++++++++++++|
For conversion of objects to strings also see concat, sconcat,
string and simplode.
Removes and returns the first byte in stream which must be a binary input stream.
If the end of file is encountered readbyte returns false.
Example: Read the first 16 bytes from a file encrypted with AES in OpenSSL.
(%i1) ibase: obase: 16.$
(%i2) in: openr_binary("msg.bin");
(%o2) #<input stream msg.bin>
(%i3) (L:[], thru 16. do push(readbyte(in), L), L:reverse(L));
(%o3) [53, 61, 6C, 74, 65, 64, 5F, 5F, 88, 56, 0DE, 8A, 74, 0FD,
0AD, 0F0]
(%i4) close(in);
(%o4) true
(%i5) map(ascii, rest(L,-8));
(%o5) [S, a, l, t, e, d, _, _]
(%i6) salt: octets_to_number(rest(L,8));
(%o6) 8856de8a74fdadf0
Removes and returns the first character in stream.
If the end of file is encountered readchar returns false.
Example: See make_string_input_stream.
Returns a string containing all characters starting at the current position
in stream up to the end of the line or false
if the end of the file is encountered.
Evaluates and displays its arguments one after the other ‘on a line’ starting at
the leftmost position. The expressions are printed with a space character right next
to the number, and it disregards line length.
newline() might be used for line breaking.
Example: Sequential printing with sprint.
Creating a new line with newline().
(%i1) for n:0 thru 19 do sprint(fib(n))$
0 1 1 2 3 5 8 13 21 34 55 89 144 233 377 610 987 1597 2584 4181
(%i2) for n:0 thru 22 do (
sprint(fib(n)),
if mod(n,10) = 9 then newline() )$
0 1 1 2 3 5 8 13 21 34
55 89 144 233 377 610 987 1597 2584 4181
6765 10946 17711
Writes byte to stream which must be a binary output stream.
writebyte returns byte.
Example: Write some bytes to a binary file output stream.
In this example all bytes correspond to printable characters and are printed
by printfile.
The bytes remain in the stream until flush_output or close have been called.
(%i1) ibase: obase: 16.$
(%i2) bytes: map(cint, charlist("GNU/Linux"));
(%o2) [47, 4E, 55, 2F, 4C, 69, 6E, 75, 78]
(%i3) out: openw_binary("test.bin");
(%o3) #<output stream test.bin>
(%i4) for i thru 3 do writebyte(bytes[i], out);
(%o4) done
(%i5) printfile("test.bin")$
(%i6) flength(out);
(%o6) 0
(%i7) flush_output(out);
(%o7) true
(%i8) flength(out);
(%o8) 3
(%i9) printfile("test.bin")$
GNU
(%i0A) for b in rest(bytes,3) do writebyte(b, out);
(%o0A) done
(%i0B) close(out);
(%o0B) true
(%i0C) printfile("test.bin")$
GNU/Linux
Next: Characters, Previous: Introduction to String Processing, Up: stringproc [Contents][Index]