https://github.com/sandialabs/parsegen-cpp

A C++17 library for parser generation for LALR(1) languages
https://github.com/sandialabs/parsegen-cpp

cmake context-free-grammar cpp cpp17 lalr-parser-generator parse parser parser-generator parser-library regular-expression sandia-national-laboratories scr-2564 snl-comp-science-libs

Last synced: 3 months ago
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A C++17 library for parser generation for LALR(1) languages

• Host: GitHub
• URL: https://github.com/sandialabs/parsegen-cpp
• Owner: sandialabs
• License: mit
• Created: 2020-12-14T19:26:51.000Z (about 4 years ago)
• Default Branch: main
• Last Pushed: 2023-01-09T23:29:37.000Z (about 2 years ago)
• Last Synced: 2024-06-14T00:22:18.846Z (8 months ago)
• Topics: cmake, context-free-grammar, cpp, cpp17, lalr-parser-generator, parse, parser, parser-generator, parser-library, regular-expression, sandia-national-laboratories, scr-2564, snl-comp-science-libs
• Language: C++
• Homepage:
• Size: 199 KB
• Stars: 12
• Watchers: 11
• Forks: 2
• Open Issues: 2
• Metadata Files:
  • Readme: README.md
  • License: LICENSE

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README

        
ParseGen

========

ParseGen is a C++17 library for working with ASCII text formats.

For example, it can parse subsets of formats like XML and YAML.

ParseGen's utility is that it is a toolbox for defining new

text languages and parsing them.

A presentation on ParseGen can be downloaded [here](https://figshare.com/articles/presentation/Parsing_Input_Files_With_ParseGen/16624408)

Theory

------

ParseGen is based on classical language theory including

regular languages, regular expressions, finite automata,

context-free grammars, and LALR(1) parsing.

Tokens are described by regular expressions and

languages are expressed as context-free grammars.

ParseGen use finite automaton theory to build table-based

lexers, and uses a fast algorithm from scientific

literature to build a table-based shift-reduce parser

for a context-free grammar.

While we acknowledge that many text formats today are not

based cleanly on context-free language theory, we

believe there is a niche to be filled by a library

like ParseGen that is still based on classical theory.

Implementation

--------------

The key contribution of ParseGen to the software community

is to implement these parser generators are pure C++

objects and functions, as opposed to tools like Flex and Bison

which have custom input formats describing languages and

output generated source code that must then be re-compiled

to obtain a parser.

A language can be built at runtime as a C++ object in ParseGen

and then a parser object can be constructed for that language

and executed repeatedly to parse C++ streams.

This offers maximum flexibility in the workflows users

can employ.

Frequently Asked Questions

--------------------------

1. How do I build it?

ParseGen uses the CMake build system and

tries to be a "standard modern CMake package" as much as possible.

2. Where do I start with the API?

The two most important classes

in ParseGen are the `language`, which fully describes a text language,

and the `parser`, which parses a language according to user-defined

rules that react to syntactic constructs observed.

The file `src/parsegen_calc.cpp` is a great introductory example

that builds a command-line calculator app using ParseGen.

3. Why C++?

C++ is the language of choice in the HPC community

that originated this code.

4. Why C++17?

We use the `std::any` feature of C++17 to allow

users to return any object as the result of parsing some text.

5. Why ASCII only, why not Unicode?

So far avoiding Unicode support has allowed a simple design

and none of the formats we target really need Unicode.

However, we welcome any contributions that move us towards

Unicode support.

At Sandia, ParseGen is SCR# 2564.0