ch2_1_when
WHEN
WHEN is a simple LISP macro built on IF. In LabLISP, WHEN is implemented as a special form. Accepts any number of arguments. The first argument - the condition - is evaluated and if it is true (not NIL), all the remaining forms are evaluated and result of the last one is returned, as in PROGN. If the condition is false, the rest is ignored and when returns NIL.
(when c f1 f2 f3) ; syntax of WHEN (if c (progn f1 f2 f3)) ; equivalent construction with IF
See also IF, PROGN, UNLESS, AND, OR
ch2_1_when.txt · Last modified: 2022/02/24 13:48 by admin