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.

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_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 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'.

Escaping to printable US-ASCII

val escape : char -> string

escape c escapes c with:

'\\' (0x5C) escaped to the sequence "\\\\" (0x5C,0x5C).
Any byte in the ranges [0x00;0x1F] and [0x7F;0xFF] escaped by an hexadecimal "\xHH" escape with H a capital hexadecimal number. These bytes are the US-ASCII control characters and non US-ASCII bytes.
Any other byte is left unchanged.

Use String.Ascii.unescape to unescape.

val escape_char : char -> string

escape_char c is like escape except is escapes s according to OCaml's lexical conventions for characters with:

'\b' (0x08) escaped to the sequence "\\b" (0x5C,0x62).
'\t' (0x09) escaped to the sequence "\\t" (0x5C,0x74).
'\n' (0x0A) escaped to the sequence "\\n" (0x5C,0x6E).
'\r' (0x0D) escaped to the sequence "\\r" (0x5C,0x72).
'\\'' (0x27) escaped to the sequence "\\'" (0x5C,0x27).
Other bytes follow the rules of escape

Use String.Ascii.unescape_string to unescape.