Validation commands

isint value

returns 1 if value is an integer, 0 if it is not
eg.:

	% isint 1
	1
	% isint a
	0
	% isint 1.2
	0

isdouble value

returns 1 if value is a real number, 0 if it is not
eg.:

	% isdouble 1.2
	1
	% isdouble 1
	1
	% isdouble a
	0