https://github.com/gabryv00/alex-happy-analyzers

Lexical analysers generators and parser generators in Haskell
https://github.com/gabryv00/alex-happy-analyzers

haskell lexical-analyzer parser-generator

Last synced: 3 months ago
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Lexical analysers generators and parser generators in Haskell

• Host: GitHub
• URL: https://github.com/gabryv00/alex-happy-analyzers
• Owner: GabryV00
• License: apache-2.0
• Created: 2023-06-28T16:06:10.000Z (almost 2 years ago)
• Default Branch: main
• Last Pushed: 2023-06-28T16:22:45.000Z (almost 2 years ago)
• Last Synced: 2025-01-13T07:31:17.149Z (5 months ago)
• Topics: haskell, lexical-analyzer, parser-generator
• Language: Haskell
• Homepage:
• Size: 3.26 MB
• Stars: 0
• Watchers: 1
• Forks: 0
• Open Issues: 0
• Metadata Files:
  • Readme: README.md
  • License: LICENSE

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README

        
# Alex-Happy-Analyzers

* **Alex** is a tool for generating lexical analysers in Haskell. It takes a description of tokens based on regular expressions and generates a Haskell module containing code for scanning text efficiently. It is similar to the tool lex or flex for C/C++.

* **Happy** is a parser generator for Haskell. Given a grammar specification in BNF, Happy generates Haskell code to parse the grammar. Happy works in a similar way to the yacc tool for C.

## Content of the repo

* **Alex 5**: Selects character strings in a text file that represent a multiple of four, in the usual decimal notation. Only numbers that are multiples of 4 are printed out, separated by a space, the rest of the text is eliminated. The divisibility check is implemented using proper regular expressions, and not the division-remainder operation.

* **Alex 8**: Recognizes strings of digits and characters, which represent numbers in one of the following formats:

  * Integers: string of decimal digits, possibly preceded by the sign (+/-)

  * Hexadecimal numbers: string of hexadecimal digits (0-9, a-f, A-F) preceded by the sequence "0x", or a string of hexadecimal digits followed by 'H'.

  * Octal numbers: string of octal digits (0-7) preceded by the sequence "0o", or a string of octal digits followed by 'O'.

* **Happy 5**: contains a lexical analyzer and a syntax analyzer to recognize a fragment of the Java language formed by:

  * Identifiers

  * Numerical constants

  * Assignment = or assignment with increment +=

  * if else

  * while loop

  * separators ; and blocks { }

  

  The parser returns the tree of the syntactic structure of the command received as input.

* **Happy 8**: contains a lexical analyzer and a syntax analyzer to recognize sequences of expressions in Scheme language formed by:

  * Identifiers

  * Integer numbers

  * Arithmetic operations: +, *, -

  * Equality test: =

  * The let and case functions

  The parser returns the parse trees of the received expressions.