How to check if a field is a number (integer or float)?

[Peng Yu]

Hi,

I am wondering what is the best way to test if a field is a number
(integer of float). I could use regex. But I am wondering if there is
a more awk-native way to do the test. Also if regex is used, what is
the regex that matches integer/float used awk. Thanks.

-- 
Regards,
Peng