https://github.com/ironholds/piton

Parsing Expression Grammars for Rcpp
https://github.com/ironholds/piton

parsing-engine parsing-expression-grammar r

Last synced: 3 days ago
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Parsing Expression Grammars for Rcpp

• Host: GitHub
• URL: https://github.com/ironholds/piton
• Owner: Ironholds
• License: other
• Created: 2017-05-20T23:57:17.000Z (over 7 years ago)
• Default Branch: master
• Last Pushed: 2020-11-02T18:59:37.000Z (almost 4 years ago)
• Last Synced: 2024-09-30T16:36:32.445Z (3 days ago)
• Topics: parsing-engine, parsing-expression-grammar, r
• Language: C++
• Size: 133 KB
• Stars: 16
• Watchers: 1
• Forks: 2
• Open Issues: 0
• Metadata Files:
  • Readme: README.md
  • License: LICENSE

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README

        
# Parsing Expression Grammars in Rcpp

[![Travis-CI Build Status](https://travis-ci.org/Ironholds/piton.svg?branch=master)](https://travis-ci.org/Ironholds/piton) [![CRAN_Status_Badge](http://www.r-pkg.org/badges/version/piton)](https://cran.r-project.org/package=piton) ![downloads](http://cranlogs.r-pkg.org/badges/grand-total/piton)

[Parsing Expression Grammars](https://en.wikipedia.org/wiki/Parsing_expression_grammar) (PEGs) are a way of defining formal grammars for formatted data that allow you to identify matched structures and then take actions on them. They're already used in R in the [readr](https://github.com/tidyverse/readr) package, which is what makes readr so dang fast at type identification and parsing tabular data, but there's not historically been a standard way of defining and using them.

`piton` changes this, provides platform-independent PEG support in Rcpp. It wraps the [PEGTL](https://github.com/taocpp/PEGTL) library by Colin Hirsch and Daniel Frey, which is header-only and so can be imported into other packages.

Please note that this project is released with a [Contributor Code of Conduct](https://github.com/Ironholds/piton/blob/master/CONDUCT.md). By participating in this project you agree to abide by its terms.

## Use

An example of PEGs is included in the package, and takes a comma-separated set of

numbers and sums them together:

```

library(piton)

peg_sum("1,2,  5, 91, 34")

[1] 133

```

`piton` itself is not designed for straight-up useR use - instead, it's a developer package. If you're interested in implementing a PEG using it, you need to:

1. Link `piton` into your package as a dependency, using `//[[Rcpp::depends()]]` (see [this post](http://gallery.rcpp.org/articles/a-first-boost-example/) for an example of how it works);

2. `#include `

3. Write and expose your grammar

4. Done!

The [PEGTL docs](https://github.com/taocpp/PEGTL/blob/master/doc/README.md) contain quite a bit of documentation on how the underlying library works, and [various examples of PEGs](https://github.com/taocpp/PEGTL/blob/master/doc/Contrib-and-Examples.md) are included within the package itself. Integration with Rcpp is pretty clean, although developers may benefit from not explicitly using the Rcpp namespace due to a couple of collisions with the `PEGTL` namespace.

## Installation

On CRAN:

```

install.packages("piton")

```

And for the development version:

```

devtools::install_github("ironholds/piton")

```