Re: [alexandria-devel] [PATCH] lazy-evaluate the default value in ENSURE-GETHASH

On 21 December 2011 20:30, Ryan Davis ryan@acceleration.net wrote:

I'm using a hash-table as a cache, and had a problem with ensure-gethash. Some example code / output:

I must be missing something. Why the CONSTANTP and LAMBDA instead of

(defmacro ensure-gethash (key hash-table &optional default) "Like GETHASH, but if KEY is not found in the HASH-TABLE saves the DEFAULT under key before returning it. Secondary return value is true if key was already in the table." `(multiple-value-bind (value ok) (gethash ,key ,hash-table) (if ok (values value ok) (values (setf (gethash ,key ,hash-table) ,default) nil))))

?

Cheers,

-- nikodemus