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### 6.3 Functions that Operate on Arrays

In this section, we describe the functions that accept all types of arrays.

Function: arrayp object

  This function returns `t` if object is an array (i.e., a vector, a string, a bool-vector or a char-table).

      (arrayp [a])
           ⇒ t
      (arrayp "asdf")
           ⇒ t
      (arrayp (syntax-table))    ;; A char-table.
           ⇒ 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

      (aref "abcdefg" 1)
           ⇒ 98           ; ‘b’ is ASCII code 98.

  See also the function `elt`, in 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. The function converts a unibyte string to multibyte if necessary to insert a character.

Function: fillarray array object

  This function fills the array array with object, so that each element of array is object. 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. See Sequence Functions.

Next: Vectors, Previous: Arrays, Up: Sequences Arrays Vectors [Contents][Index]