If a regex is required to only match x if p(x), is the regex required to match A...

jakobsen · on Jan 7, 2014

Of course it is required (within the computational limits of your computer, of course)

If p(x) means 'x is an integer', you could use the regex /^1$/ since it matches integers only (in particular, the integer 1). That's not sufficient, you need to match all integers.

edited:format

algorias · on Jan 7, 2014

It's required to match all such x, otherwise the empty regex "" trivially satisfies the requirement.