XLISP when

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# when

Type: | - | special form (fsubr)
Source: | - | xlcont.c

## Syntax

(when test [expr ... ])
  test - an expression, NIL or non-NIL
  expr - expressions comprising a body of code
  returns - the value of the last expression or NIL

## Description

The 'when' macro executes the 'expr' forms if 'test' evaluates to a non-NIL value. If 'test' is non-NIL , the value of the last 'expr' is returned as the result. If 'test' is NIL , NIL is returned with none of 'expr' evaluated.

## Examples

    (when NIL)                  ; returns NIL
    (when T)                    ; returns T

    (when T (print "hi") 'foo)  ; prints "hi"  returns FOO

    (when (listp '(a))
          (print "a list"))     ; prints  "a list"
                                ; returns "a list"

See the when special form in the XLISP 2.0 manual.

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Nyquist / XLISP 2.0 - Contents | Tutorials | Examples | Reference