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and
Type: |
- |
special form (fsubr) |
Source: |
- |
xlcont.c |
Syntax
- (and [expr1 ... ])
- exprN - an expression
returns - NIL if any expression evaluates
to NIL , otherwise the value
of the last expression
Note: evaluation of expressions stops after the first
expression that evaluates to NIL
Description
The 'and' special form evaluates a sequence of expressions and returns
the effect of a logical AND on the expressions. If, at any
point, an expression is NIL, then
NIL is returned as the result of the 'and'
function. If all of the expressions have a
non-NIL value, the value of the last
expression is returned as the result. Evaluation of the expressions will
stop when an expression evaluates to NIL,
none of the subsequent expressions will be evaluated. If there
are no expressions, then 'and' returns T
as its result.
Examples
(and t t t) => T
(and nil t) => NIL
(and t nil) => NIL
(and) => T
Some more practical examples:
> (and T "boo" "hiss" T "rah")
"rah" ; return value of AND
> (and (princ "hi") NIL (princ "ho"))
hi ; prints "hi"
NIL ; return value of AND
See princ.
> (setq a 5 b 6) ; set up A and B
6 ; return value of SETQ
> (if (and (numberp a) ; if A is a number
(numberp b) ; and B is a number
(< a b)) ; and A < B
(print "A is less than B") ; then do this
(print "error")) ; else do this
"A is less than B" ; screen output of PRINT
"A is less than B" ; return value of IF
See < ,
if , print,
setq.
See also:
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