That module has functions that test whether a character is of a certain type.
nimble install asciitype
import asciitype
var
a = 'f'
b = "FOO1"
c = "fhioeFKOhu47893joi983FFd"
doAssert a.isPrint == true
doAssert b.isUpper == false
doAssert b.isUpper(true) == true
doAssert c.isAnyType({upper, lower, num}) == true
doAssert ' '.isAnyType({space}) == true