isinteger - Checks for a digit (0 through 9) that may be preceed by + or -.
isinteger("…");
This function is used to determine if the argument is a digit, that is an arabic number contained between 0 and 9 and maybe start with + or -. The argument can be a single character or a string. In the latter case, each character has to be a digit for the function to be true.
Written by Pierre Laplante and Caroline Laplante, <laplante@sednove.com>
1.0 2014-09-09 21:24:14 laplante@sednove.com