dc_regex Module Reference

Provides simple regular expression subroutine: 'match'. More...

Functions/Subroutines
subroutine, public	match (pattern, text, start, length)

Detailed Description

Provides simple regular expression subroutine: 'match'.

Author

Youhei SASAKI

Copyright

Copyright (C) GFD Dennou Club, 2000-2026. All rights reserved.
License is BSD-2-Clause. see COPYRIGHT in detail

This module provides a simple regular expression matching function.

Supported Features

Pattern	Description
.	Any single character
?	Zero or one of previous
+	One or more of previous
*	Zero or more of previous
^	Beginning of string
$	End of string
[abc]	Character class
[^abc]	Negated character class
#d	Digit (0-9)
#a	Alphabetic character
#w	Word character (alphanumeric + _)
#s	Whitespace
#z	Hexadecimal digit
#xHH	Hexadecimal character code

Note

The escape character is '#' instead of '\'.

Function/Subroutine Documentation

match()

subroutine, public dc_regex::match	(	character(len = *), intent(in)	pattern,
		character(len = *), intent(in)	text,
		integer, intent(out)	start,
		integer, intent(out)	length )

Match regular expression pattern against text

Matches the given regular expression pattern against the text string.

If pattern matches text, start returns the position (1-based) where the match begins, and length returns the number of matched characters.

If no match is found, length == -1 and start == 0.

Parameters

[in]	pattern	Regular expression pattern
[in]	text	Text string to search
[out]	start	Starting position of match (0 if no match)
[out]	length	Length of match (-1 if no match)

Example

program regex_test
  use dc_regex, only: match
  use dc_types, only: token
  implicit none
  integer:: start, length
  character(TOKEN) :: pattern, text
 
  pattern = 
  text    = 
  call match(trim(pattern), trim(text), start, length)
  ! Result: start=5, length=2
 
  pattern = 
  text    = 
  call match(trim(pattern), trim(text), start, length)
  ! Result: start=1, length=7
 
  pattern = 
  text    = 
  call match(trim(pattern), trim(text), start, length)
  ! Result: start=8, length=3
end program regex_test

Definition at line 468 of file dc_regex.f90.

    implicit none
    character(len = *), intent(in)  :: pattern, text
    integer, intent(out)            :: start, length
    integer, allocatable            :: ipattern(:)
    integer                         :: text_length
    continue
    ! 空 pattern は空文字列に適合
    if (len(pattern) <= 0) then
      length = 0
      start = 1
      return
    endif
    ! メタキャラクタの認識
    allocate(ipattern(len(pattern) + 2))
    call preprocess_pattern(pattern, ipattern)
    ! 頭寄せ指定のある場合
    if (ipattern(1) == sym_headfix) then
      start = 1
      call match_here(ipattern(2: ), text, length)
      if (length < 0) goto 995
      goto 999
    end if
    ! 最左原理
    text_length = len(text)
    do, start = 1, text_length + 1
      call match_here(ipattern, text(start:text_length), length)
      if (length >= 0) goto 999
    end do
    ! みつからない場合
995 continue
    start = 0
    length = -1
999 continue
    deallocate(ipattern)