The standard library int_chartype package implements C-style predicates on characters. This is modelled after the Unix C libraries. Each predicate comes in two forms; one that works on integers, and one that works on an arbitrary character in a string. The meanings of these predicates are documented in Section 3 of the Unix manual.
The int_chartype package implements the Int_Chartype API.
The Int_Chartype api source code is in src/lib/std/src/int-chartype.pkg.
See also: String_Chartype. The above information is manually maintained and may contain errors.