RE: concat vs format

[Drew Adams]

> Is there a difference between:
> (concat firstPartofURL secondPartofURL) and
> (format "%s%s" firstPartofURL secondPartofURL)?

If both args are strings then no; the result
is the same.  But the functions are very
different - they take different args and,
aside from some cases like this one where
the result is the same for some args, their
uses/purposes are different.