Macro dotimes

Syntax:

Arguments and Values:

var—a symbol.

count-form—a form.

result-form—a form.

declaration—a declare expression; not evaluated.

tag—a go tag; not evaluated.

statement—a compound form; evaluated as described below.

7.8.3 4results—if a return or return-from form is executed, the values passed from that form; otherwise, the values returned by the result-form or nil if there is no result-form.

Description:

7.8.3 9dotimes iterates over a series of integers.

dotimes evaluates count-form, which should produce an integer. If count-form is zero or negative, the body is not executed. dotimes then executes the body once for each integer from 0 up to but not including the value of count-form, in the order in which the tags and statements occur, with var bound to each integer. Then result-form is evaluated. At the time result-form is processed, var is bound to the number of times the body was executed. Tags label statements.

An implicit block In effect, a \specref{block}named nil surrounds dotimes. 7.8.3 5 7.8.3 10return may be used to terminate the loop immediately without performing any further iterations, returning zero or more values.

The body of the loop is an implicit tagbody; it may contain tags to serve as the targets of go statements. Declarations may appear before the body of the loop.

Per Loosemore #28 For \macref{dotimes}, the \term{scope} of the name binding does not include any initial value form, but the stepper and optional result forms are included.The scope of the binding of var does not include the count-form, but the result-form is included.

Added per Loosemore #27, first public reviewIt is implementation-dependent whether dotimes establishes a new binding of var on each iteration or whether it establishes a binding for var once at the beginning and then assigns it on any subsequent iterations.

Examples:

 (dotimes (temp-one 10 temp-one)) → 10
 (setq temp-two 0) → 0
 (dotimes (temp-one 10 t) (incf temp-two)) → T
 temp-two → 10

7.8.3 11

Here is an example of the use of dotimes in processing strings:

;;; True if the specified subsequence of the string is a
;;; palindrome (reads the same forwards and backwards).
 (defun palindromep (string &optional
                           (start 0)
                           (end (length string)))
   (dotimes (k (floor (- end start) 2) t)
    (unless (char-equal (char string (+ start k))
                        (char string (- end k 1)))
      (return nil))))
 (palindromep "Able was I ere I saw Elba") → T
 (palindromep "A man, a plan, a canal--Panama!") → NIL
 (remove-if-not #'alpha-char-p          ;Remove punctuation.
               "A man, a plan, a canal--Panama!")
→ "AmanaplanacanalPanama"
 (palindromep
  (remove-if-not #'alpha-char-p
                "A man, a plan, a canal--Panama!")) → T
 (palindromep
  (remove-if-not
   #'alpha-char-p
   "Unremarkable was I ere I saw Elba Kramer, nu?")) → T
 (palindromep
  (remove-if-not
   #'alpha-char-p
   "A man, a plan, a cat, a ham, a yak,
                  a yam, a hat, a canal--Panama!")) → T

Side Effects:

None.

Affected By:

None.

Exceptional Situations:

None.

See Also:

do, dolist, tagbody

Notes:

go may be used within the body of dotimes to transfer control to a statement labeled by a tag.