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https://github.com/perazz/fortran-regex
Fortran port of the tiny-regex-c library
https://github.com/perazz/fortran-regex
fortran regex regex-parser regular-expression regular-expressions
Last synced: about 11 hours ago
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Fortran port of the tiny-regex-c library
- Host: GitHub
- URL: https://github.com/perazz/fortran-regex
- Owner: perazz
- License: mit
- Created: 2022-08-26T16:01:37.000Z (over 2 years ago)
- Default Branch: main
- Last Pushed: 2024-03-26T12:44:30.000Z (10 months ago)
- Last Synced: 2024-03-26T13:49:02.194Z (10 months ago)
- Topics: fortran, regex, regex-parser, regular-expression, regular-expressions
- Language: Fortran
- Homepage:
- Size: 209 KB
- Stars: 20
- Watchers: 3
- Forks: 1
- Open Issues: 0
-
Metadata Files:
- Readme: README.md
- License: LICENSE
Awesome Lists containing this project
README
### fortran-regex
Fortran-regex is a Modern Fortran port of the [tiny-regex-c](https://github.com/kokke/tiny-regex-c) library for regular expressions. It is based on the original C implementation, but the API is modelled in Fortran style, which is similar to the intrinsic `index` function.
### API
The main API is modelled around Fortran's `index` intrinsic function (which performs a simple search for a substring within a string):
```fortran
! Perform regex on a character string
result = REGEX(string, pattern [, length] [, [back]])
```
- If the pattern command is invalid, `result = -1`.
- If no substrings with the given pattern are found, with a valid pattern `result = 0`. This is also returned if the string has zero length, and that is an acceptable answer for the input pattern.
- Otherwise, if the pattern was found `result > 0` equal to the leftmost location inside the string where the pattern can be found. If the `back` keyword is provided and `.true.`, the location of the rightmost occurrence is returned instead. `length` returns the number of consecutive characters that match this pattern
### Arguments
| Argument | Type | Intent | Description |
| --- | --- | --- | --- |
| `string` | `character(*)` | `in` | The input text |
| `pattern` | `character(*)` | `in` | The regex command |
| `length` | `integer` | `out` (optional) | Length of the matched pattern |
| `back` | `logical` | `in` (optional) | If the BACK argument is present and `.true.`, the return value is the start of the last occurrence rather than the first. |
### Object-oriented interface
One can also parse a regex pattern into a `type(regex_pattern)` structure, and use that instead of a string pattern. I have no idea why this should be useful, but at least it's given with a consistent interface
### Overview
The original tiny-regex-c code has been significantly refactored, to:
* Remove all references to `NULL` character string termination, and replace them with Fortran's string intrinsics (`len`, `len_trim`, etc.)
* Remove all C escaped characters (`\n`, `\t`, etc), replace with Fortran syntax.
* Even in presence of strings, use `pure` `elemental` functions wherever possible
* It is a standalone module that has no external dependencies besides compiler modules.
### Example programs
```fortran
! Demonstrate use of regex
program test_regex
use regex_module
implicit none
integer :: idx,ln
character(*), parameter :: text = 'table football'
idx = REGEX(string=text,pattern='foo*',length=ln);
! Prints "foo"
print *, text(idx:idx+ln-1)
end program
```
```fortran
! Demonstrate use of object-oriented interface
program test_regex
use regex_module
implicit none
integer :: idx,ln
character(*), parameter :: text = 'table football'
type(regex_pattern) :: re
! Parse pattern into a regex structure
re = parse_pattern('foo*')
idx = REGEX(string=text,pattern=re,length=ln);
! Prints "foo"
print *, text(idx:idx+ln-1)
end program
```
### To do list
- [X] Add a `BACK` optional keyword to return the last instance instead of the first.
- [ ] Option to return ALL instances as an array, instead of the first/last one only.
- [X] Replace fixed-size static storage with allocatable character strings (slower?)
### Reporting problems
Please report any problems! It is appreciated. The original C library had hacks to account for the fact that several special characters are read in with escaped sequences, which partially collides with the escaped sequence options in regex. So, expect the current API to be still a bit rough around the edges.
### License
fortran-regex is released under the MIT license. The code it's based upon is in the public domain.