The CharMap structure

The CharMap structure provides fast, read-only, maps from 8-bit characters to values.

Synopsis

signature CHAR_MAP
structure CharMap :> CHAR_MAP

Interface

type 'a char_map

val mkCharMap : {default : 'a, bindings : (string * 'a) list} -> 'a char_map

val mapChr : 'a char_map -> char -> 'a
val mapStrChr : 'a char_map -> (string * int) -> 'a

Description

type 'a char_map

The type of a mapping from 8-bit characters to 'a.

val mkCharMap : {default : 'a, bindings : (string * 'a) list} -> 'a char_map

mkCharMap {default, bindings} creates a new character map. For each item (s, v) in the bindings list, the characters in s are mapped to the value v. If a character is bound multiple times, then the rightmost binding is used. Characters not covered by a binding are mapped to the default value. For example, the following code creates a mapping that classifies characters into lower and upper case letter, digits, and other characters:

datatype char_kind = LOWER | UPPER | DIGIT | OTHER

val cmap = mkCharMap {
        default = OTHER,
        bindings = [
            ("abcdefghijklmnopqrstuvwxyz", LOWER),
            ("ABCDEFGHIJKLMNOPQRSTUVWXYZ", UPPER),
            ("0123456789", DIGIT)
          ]
      }
val mapChr : 'a char_map -> char -> 'a

mapChr cmap c applies the map to the character.

val mapStrChr : 'a char_map -> (string * int) -> 'a

mapStrChr cmap (s, i) applies the map to the i`th character in `s. The Subscript exception is raised if i is out of bounds.

See Also

The Util Library