Module `Char.Ascii`

US-ASCII character support.

The following functions act only on US-ASCII code points, that is on the bytes in range [0x00;0x7F]. The functions can be safely used on UTF-8 encoded strings, they will of course only deal with US-ASCII related matters.

References.

Vint Cerf. ASCII format for Network Interchange. RFC 20, 1969.

Decimal and hexadecimal digits

val is_digit : char -> bool: is_digit c is true iff c is an US-ASCII digit '0' ... '9', that is a byte in the range [0x30;0x39].

val is_hex_digit : char -> bool: is_hex_digit c is true iff c is an US-ASCII hexadecimal digit '0' ... '9', 'a' ... 'f', 'A' ... 'F', that is a byte in one of the ranges [0x30;0x39], [0x41;0x46], [0x61;0x66].

val hex_digit_value : char -> int

hex_digit_value c is the numerical value of a digit that satisfies is_hex_digit.

raises Invalid_argument: if is_hex_digit c is false.

val lower_hex_digit : int -> char: lower_hex_digit n is an hexadecimal digit for the integer n truncated to its lowest 4 bits.

val upper_hex_digit : int -> char: upper_hex_digit n is an hexadecimal digit for the integer n truncated to its lowest 4 bits.

Predicates

val is_valid : char -> bool: is_valid c is true iff c is an US-ASCII character, that is a byte in the range [0x00;0x7F].

val is_upper : char -> bool: is_upper c is true iff c is an US-ASCII uppercase letter 'A' ... 'Z', that is a byte in the range [0x41;0x5A].

val is_lower : char -> bool: is_lower c is true iff c is an US-ASCII lowercase letter 'a' ... 'z', that is a byte in the range [0x61;0x7A].

val is_letter : char -> bool: is_letter c is is_lower c || is_upper c.

val is_alphanum : char -> bool: is_alphanum c is is_letter c || is_digit c.

val is_white : char -> bool: is_white c is true iff c is an US-ASCII white space character, that is one of space ' ' (0x20), tab '\t' (0x09), newline '\n' (0x0A), vertical tab (0x0B), form feed (0x0C), carriage return '\r' (0x0D).

val is_blank : char -> bool: is_blank c is true iff c is an US-ASCII blank character, that is either space ' ' (0x20) or tab '\t' (0x09).

val is_graphic : char -> bool: is_graphic c is true iff c is an US-ASCII graphic character that is a byte in the range [0x21;0x7E].

val is_print : char -> bool: is_print c is is_graphic c || c = ' '.

val is_control : char -> bool: is_control c is true iff c is an US-ASCII control character, that is a byte in the range [0x00;0x1F] or 0x7F.

Casing transforms

val uppercase : char -> char: uppercase c is c with US-ASCII characters 'a' to 'z' mapped to 'A' to 'Z'.

val lowercase : char -> char: lowercase c is c with US-ASCII characters 'A' to 'Z' mapped to 'a' to 'z'.