(lispref.info)Array Functions


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Functions that Operate on Arrays
================================

   In this section, we describe the functions that accept both strings
and vectors.

 - Function: arrayp OBJECT
     This function returns `t' if OBJECT is an array (i.e., either a
     vector or a string).

          (arrayp [a])
          => t
          (arrayp "asdf")
          => t

 - Function: aref ARRAY INDEX
     This function returns the INDEXth element of ARRAY.  The first
     element is at index zero.

          (setq primes [2 3 5 7 11 13])
               => [2 3 5 7 11 13]
          (aref primes 4)
               => 11
          (elt primes 4)
               => 11
          
          (aref "abcdefg" 1)
               => 98           ; `b' is ASCII code 98.

     See also the function `elt', in Note: Sequence Functions.

 - Function: aset ARRAY INDEX OBJECT
     This function sets the INDEXth element of ARRAY to be OBJECT.  It
     returns OBJECT.

          (setq w [foo bar baz])
               => [foo bar baz]
          (aset w 0 'fu)
               => fu
          w
               => [fu bar baz]
          
          (setq x "asdfasfd")
               => "asdfasfd"
          (aset x 3 ?Z)
               => 90
          x
               => "asdZasfd"

     If ARRAY is a string and OBJECT is not a character, a
     `wrong-type-argument' error results.

 - Function: fillarray ARRAY OBJECT
     This function fills the array ARRAY with pointers to OBJECT,
     replacing any previous values.  It returns ARRAY.

          (setq a [a b c d e f g])
               => [a b c d e f g]
          (fillarray a 0)
               => [0 0 0 0 0 0 0]
          a
               => [0 0 0 0 0 0 0]
          (setq s "When in the course")
               => "When in the course"
          (fillarray s ?-)
               => "------------------"

     If ARRAY is a string and OBJECT is not a character, a
     `wrong-type-argument' error results.

   The general sequence functions `copy-sequence' and `length' are
often useful for objects known to be arrays.  Note: Sequence
Functions.


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