LR-demo: An LALR parsetable generator and interpreter.

This is a package candidate release! Here you can preview how this package release will appear once published to the main package index (which can be accomplished via the 'maintain' link below). Please note that once a package has been published to the main package index it cannot be undone! Please consult the package uploading documentation for more information.

[maintain] [Publish]

Warnings:

[no-description] No 'description' field.
[missing-upper-bounds] On library, these packages miss upper bounds: - array - containers - microlens - microlens-th - mtl - string-qq - transformers Please add them. There is more information at https://pvp.haskell.org/
[missing-upper-bounds] On custom-setup, these packages miss upper bounds: - process Please add them. There is more information at https://pvp.haskell.org/

[Skip to Readme]

Properties

Versions	0.0.20241111
Change log	None available
Dependencies	array, base (>=4.11 && <5), containers, LR-demo, microlens, microlens-th, mtl, string-qq, transformers [details]
License	BSD-3-Clause
Author	Andreas Abel <andreas.abel@gu.se>
Maintainer	Andreas Abel <andreas.abel@gu.se>
Category	Parsing
Uploaded	by AndreasAbel at 2024-11-11T23:08:31Z

Modules

CFG
CharacterTokenGrammar
DebugPrint
LBNF
- LBNF.Abs
- LBNF.Lex
- LBNF.Par
- LBNF.Print
LR
License
ParseTable
- ParseTable.Pretty
Paths_LR_demo
Saturation
SetMaybe
Util

Downloads

LR-demo-0.0.20241111.tar.gz [browse] (Cabal source package)
Package description (as included in the package)

Maintainer's Corner

Package maintainers

AndreasAbel

For package maintainers and hackage trustees

edit package information

Readme for LR-demo-0.0.20241111

[back to package description]

A parser for LALR(1) grammars in Haskell

Usage:

lr-demo MyGrammar.cf < MyInput.txt

Prints the generated LALR(1) parse table for context-free grammar MyGrammar.cf and a trace of shift and reduce actions of the parser when accepting MyInput.txt.

The input .cf file consists of labelled BNF rules (LBNF) of the form:

LABEL "." NONTERMINAL "::=" (NONTERMINAL | TERMINAL)* ";"

For example:

Par.  S ::= "(" S ")" S ;
Done. S ::= ;

This format is compatible with BNFC (but BNFC pragmas are not recognized).

Limitation: terminals can only be single characters.

Getting started

Have Haskell Stack installed.
Clone and enter this repository.
Execute: stack run lr-demo -- test/BalancedParentheses.cf < test/BalPar.txt

Using the following grammar:

Done . S ::=;
Par . S ::= "(" S ")" S;

Generated parse table:

State 0

	eof	reduce with rule Done
	'('	shift to state 1

	S 	goto state 2

State 1

	'('	shift to state 1
	')'	reduce with rule Done

	S 	goto state 3

State 2

	eof	reduce with rule %start

State 3

	')'	shift to state 4

State 4

	eof	reduce with rule Done
	'('	shift to state 1
	')'	reduce with rule Done

	S 	goto state 5

State 5

	eof	reduce with rule Par
	')'	reduce with rule Par


Parsing stdin...
            . '(' ')'  -- shift
'('         . ')'      -- reduce with rule Done
'(' S       . ')'      -- shift
'(' S ')'   .          -- reduce with rule Done
'(' S ')' S .          -- reduce with rule Par
S           .          -- halt

Reference

stack run -- --help

License

BSD 3-clause.