How to read an integer from the minibuffer

[Marcin Borkowski]

Hi all,

I'd like to read an integer (or something else e.g. matching a regex)
from a minibuffer.  Basically, I'm after a version of `read-string', but
either allowing only some characters, or accepting only input matching
some regex (possibly both).

How do I do that?  One way would be to use `read-from-minibuffer' with
a suitable keymap, but that seems slightly low-level.  If that is the
way to go, is there a good way to set up a keymap so that nothing except
some specified characters are self-inserting?  IOW, is `suppress-keymap'
the way to go or is there some other way?

TIA,

-- 
Marcin Borkowski
http://mbork.pl