## 21. Lambda

If you just want to create a temporary function and don't want to bother giving it a name, `lambda` is what you need.

> `

>     > #'(lambda (x) (+ x 3))
>     (LAMBDA (X) (+ X 3))
>     > (funcall * 5)               ;* is the last result,remember?
>     8
>     <tscreen><verb>

>     The combination of <tt/lambda/ and <tt/mapcar/ can replace many loops. For
>     example, the following two forms are equivalent:

>     <tscreen><verb>
>     > (do ((x '(1 2 3 4 5) (cdr x))
>            (y nil))
>           ((null x) (reverse y))
>         (push (+ (car x) 2) y))
>     (3 4 5 6 7)
>     > (mapcar #'(lambda (x) (+ x 2)) '(1 2 3 4 5))
>     (3 4 5 6 7)

> `

However the first version will run significantly faster when compiled by CMUCL. But speed isn't everything and the second version is a lot clearer and easier to debug.