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and `dotimes`

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`dotimes`

MacroThe `dotimes`

macro is similar to `dolist`

, except that it
loops a specific number of times.

The first argument to `dotimes`

is assigned the numbers 0, 1, 2
and so forth each time around the loop. You need to provide the value
of the second argument, which is how many times the macro loops.

For example, the following binds the numbers from 0 up to, but not
including, the number 3 to the first argument, `number`, and then
constructs a list of the three numbers. (The first number is 0, the
second number is 1, and the third number is 2; this makes a total of
three numbers in all, starting with zero as the first number.)

(let (value) ; otherwise a value is a void variable (dotimes (number 3) (setq value (cons number value))) value) ⇒ (2 1 0)

The way to use `dotimes`

is to operate on some expression
`number` number of times and then return the result, either as
a list or an atom.

Here is an example of a `defun`

that uses `dotimes`

to add
up the number of pebbles in a triangle.

(defun triangle-using-dotimes (number-of-rows) "Using `dotimes', add up the number of pebbles in a triangle." (let ((total 0)) ; otherwise a total is a void variable (dotimes (number number-of-rows) (setq total (+ total (1+ number)))) total)) (triangle-using-dotimes 4)