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mapcar

mapcar

type: function (subr) 
location: built-in
source file: xllist.c
Common LISP compatible: yes
supported on: all machines

SYNTAX

(mapcar <function> <list1> [ <list2> ... ] )
        <function>      -       a function definition (like a LAMBDA) 
                                or a function name
        <listN>         -       a list or list expression

DESCRIPTION

MAPCAR applies the <function> to the succesive CARs of each of the lists <listN>. Each of the lists supplies one of the arguments to <function>. The MAPCAR function returns a list that is constructed from the results of the <function> applications. If the lists are of different lengths, the shortest list will determine the number of applications of <function>.

EXAMPLES

(mapcar '+ '(1 2 3) '(1 2 3))           ; returns (2 4 6)
(mapcar 'princ '(1 2 3))                ; prints 123
                                        ;   returns (1 2 3)
(mapcar '+ '(1 2 3)                     ; different length lists
           '(1 2 3 4 5 6))              ;   returns (2 4 6)

NOTE: The use of the <function> will work properly when it is a quoted symbol (which is the name of the function), an unquoted symbol (whose value is a function) or a closure object (like a LAMBDA).

BUG NOTE: The proper syntax for <function> when <function> is a lambda expression is, for example (mapcar #'(lambda (arg1 arg2) (+ arg1 arg2)) '(1 2)), NOT (mapcar '(lambda (arg1 arg2) (+ arg1 arg2)) '(1 2)). That is, the #' read macro must be present. This error should be caught by the xlisp interpreter, but it is not, with the result that very obscure garbage collection bugs occur.


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