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(librep.info)Sequence Functions

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Sequence Functions
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 - Function: sequencep arg
     Returns true if ARG is a sequence, i.e. a list or an array.

 - Function: length sequence
     This function returns the length (an integer) of the sequence
     SEQUENCE.

          (length "abc")
              => 3
          
          (length '(1 2 3 4))
              => 4
          
          (length [x y])
              => 2

 - Function: copy-sequence sequence
     Returns a new copy of the sequence SEQUENCE. Where possible (in
     lists and vectors) only the `structure' of the sequence is newly
     allocated: the same objects are used for the elements in both
     sequences.

          (copy-sequence "xy")
              => "xy"
          
          (setq x '("one" "two"))
              => ("one" "two")
          (setq y (copy-sequence x))
              => ("one" "two")
          (eq x y)
              => ()
          (eq (car x) (car y))
              => t

 - Function: elt sequence position
     This function returns the element of SEQUENCE POSITION elements
     from the beginning of the sequence.

     This function is a combination of the `nth' and `aref' functions.

          (elt [0 1 2 3] 1)
              => 1
          
          (elt '(foo bar) 0)
              => foo