CL Enumerations: Standard Generic Function HAS-PREVIOUS-P
 

Generic function HAS-PREVIOUS-P

Package:

CL.EXTENSIONS.ENUMERATIONS

Syntax:

  has-previous-p enumeration
  => result
  

Arguments and Values:

enumeration---a bi-directional enumeration instance

result---a generalized boolean

Description:

The generic function HAS-PREVIOUS-P checks whether the bi-directional enumeration enumeration has another element that precedes the current one in the traversal order. If so it returns a non-NIL result, otherwise, result is NIL.

Examples:

  cl-prompt> (defvar ve (enumerate (vector 1 2 3)))
  VE

  cl-prompt> (has-previous-p ve)
  NIL

  cl-prompt> (next ve)
  1

  cl-prompt> (has-previous-p ve)
  T
  

Affected By:

None.

Exceptional Situations:

HAS-PREVIOUS-P is not defined for non BI-DIRECTIONAL-ENUMERATIONs.

See Also:

ENUMERATION class, NEXT, HAS-NEXT-P, CURRENT, PREVIOUS, NO-SUCH-ELEMENT.

Notes:

None.