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(emacs-lisp-intro.info)Decrementing Loop

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Loop with a Decrementing Counter
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   Another common way to write a `while' loop is to write the test so
that it determines whether a counter is greater than zero.  So long as
the counter is greater than zero, the loop is repeated.  But when the
counter is equal to or less than zero, the loop is stopped.  For this
to work, the counter has to start out greater than zero and then be
made smaller and smaller by a form that is evaluated repeatedly.

   The test will be an expression such as `(> counter 0)' which returns
`t' for true if the value of `counter' is greater than zero, and `nil'
for false if the value of `counter' is equal to or less than zero.  The
expression that makes the number smaller and smaller can be a simple
`setq' such as `(setq counter (1- counter))', where `1-' is a built-in
function in Emacs Lisp that subtracts 1 from its argument.

   The template for a decrementing `while' loop looks like this:

     (while (> counter 0)                    ; true-or-false-test
       BODY...
       (setq counter (1- counter)))          ; decrementer

Decrementing Example

More pebbles on the beach.

Dec Example parts

The parts of the function definition.

Dec Example altogether

Putting the function definition together.