The RegExpFn functor

The RegExpFn functor glues together a front-end regular-expression parser with a back-end regular-expression engine.

Synopsis

signature REGEXP
functor RegExpFn (
    structure P : REGEXP_PARSER
    structure E : REGEXP_ENGINE
  ) :> REGEXP where type regexp = E.regexp

Functor Argument Interface

structure P : REGEXP_PARSER
structure E : REGEXP_ENGINE

Functor Argument Description

structure P : REGEXP_PARSER

The front-end parser for the regular-expression syntax.

structure E : REGEXP_ENGINE

The back-end engine.

Interface

type regexp

type 'a match = {pos : 'a, len : int} MatchTree.match_tree

exception CannotParse

val compile : (char,'a) StringCvt.reader -> (regexp, 'a) StringCvt.reader
val compileString : string -> regexp

val find : regexp -> (char,'a) StringCvt.reader -> ('a match, 'a) StringCvt.reader

val prefix : regexp -> (char,'a) StringCvt.reader -> ('a match, 'a) StringCvt.reader

val match : (string * ('a match -> 'b)) list
      -> (char,'a) StringCvt.reader -> ('b, 'a) StringCvt.reader

Interface Description

type regexp

The type of a compiled regular expression.

(* a match specifies the position (as a stream) and the length of the match *)
type 'a match = {pos : 'a, len : int} MatchTree.match_tree

A match tree specifying the starting position and size of matches. For a general character reader getc, we can extract the string for a match using the following function:

fun getMatchString {pos, len} = let
      fun get (_, 0, chrs) = String.implodeRev chrs
        | get (strm, n, chrs) = let
            val SOME(c, rest) = getc strm
            in
              get (rest, n-1, c::chrs)
            end
      in
        get (pos, len, [])
      end

More direct means are possible for specific input sources (e.g., strings, substrings, or text input).

exception CannotParse

This exception is raised by the functions compileString match when the front-end encounters a syntax error.

val compile : (char,'a) StringCvt.reader -> (regexp, 'a) StringCvt.reader

compile getc strm parses and compiles a regular expression from the input stream strm using the character reader getc. If successful, it returns SOME(re, strm'), where re is the compiled regular expression and strm' is the residual input stream. It returns NONE if there is a syntax error in the input. If the source regular expression contains features that are not supported by the back-end engine, then the CannotCompile exception is raised.

val compileString : string -> regexp

compileString s returns the compiled regular expression defined by the string s. The CannotParse exception is raised if there was a syntax error when parsing s and the CannotCompile exception is raised if the source regular expression contains features that are not supported by the back-end engine.

val find : regexp -> (char,'a) StringCvt.reader -> ('a match, 'a) StringCvt.reader

find re getc strm returns SOME mt where mt describes the first match of re in the input stream; otherwise it returns NONE if there is no match.

val prefix : regexp -> (char,'a) StringCvt.reader -> ('a match, 'a) StringCvt.reader

prefix re getc strm returns SOME mt where mt describes the matching of re at the beginning of the input stream; otherwise it returns NONE if re does not match a prefix of the input.

val match : (string * ('a match -> 'b)) list -> (char,'a) StringCvt.reader -> ('b, 'a) StringCvt.reader

match rules getc strm attempts to match one of the rules starting at the current stream position. Each rule is a pair of a regular expression and an action. The rules are tested in order; if a rule (re, act) matches with the result mt, then the result of match will be SOME(act mt). If no rule matches, then NONE is the result.

See Also

The RegExp Library