https://github.com/egnha/dub

Unpacking assignment via pattern matching
https://github.com/egnha/dub

pattern-matching r unpacking-assignment

Last synced: 3 months ago
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Unpacking assignment via pattern matching

• Host: GitHub
• URL: https://github.com/egnha/dub
• Owner: egnha
• License: other
• Created: 2018-02-08T07:13:13.000Z (almost 7 years ago)
• Default Branch: master
• Last Pushed: 2018-10-28T14:07:22.000Z (about 6 years ago)
• Last Synced: 2024-10-01T16:36:57.643Z (4 months ago)
• Topics: pattern-matching, r, unpacking-assignment
• Language: R
• Homepage:
• Size: 99.6 KB
• Stars: 10
• Watchers: 2
• Forks: 1
• Open Issues: 1
• Metadata Files:
  • Readme: README.Rmd
  • License: LICENSE

Awesome Lists containing this project

README

        
---

output: github_document

---

```{r setup, include = FALSE}

knitr::opts_chunk$set(

  collapse = TRUE,

  comment = "#>",

  fig.path = "man/figures/README-",

  out.width = "100%"

)

```

[![Travis build status](https://travis-ci.org/egnha/dub.svg?branch=master)](https://travis-ci.org/egnha/dub)

[![Coverage status](https://codecov.io/gh/egnha/dub/branch/master/graph/badge.svg)](https://codecov.io/github/egnha/dub?branch=master)

[![CRAN_Status_Badge](http://www.r-pkg.org/badges/version/dub)](https://cran.r-project.org/package=dub)

# dub

_dub_ is a small, single-purpose R package for _unpacking assignment_: it provides an operator `%<<-%` that enables you to assign (nested) components of a list (or vector) to names via pattern matching. The pattern matching syntax mirrors the semantics of `list()`. Think of the “dub(ble) arrow” `<<-` as a pictograph representing multiple `<-`'s.

```{r}

library(dub)

(one : two : three) %<<-% 1:3

one

two

three

(x) %<<-% list(list("x"))

((y)) %<<-% list(list("y"))

x

y

(u : (v : w)) %<<-% list(1, list(2, 3:4))

u

v

w

# Use . to drop specific components, ... to drop greedily (the _ in Haskell)

(. : width : ... : species) %<<-% iris

head(width)

head(species)

```

More details and examples are in the package documentation (`` ?`%<<-%` ``).

## Installation

Install from CRAN:

``````{r, eval = FALSE}

install.packages("dub")

```

Alternatively, install the development version from GitHub:

```{r gh-installation, eval = FALSE}

# install.packages("devtools")

devtools::install_github("egnha/dub")

```

## Prior art

Unpacking/multiple assignment appears in other languages (e.g., [Python](https://docs.python.org/3/tutorial/datastructures.html#tuples-and-sequences), [JavaScript](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Destructuring_assignment), [Clojure](https://clojure.org/guides/destructuring)). While R has no such feature, using a custom operator to do this has long been a folklore method. To my knowledge, the earliest implementation is by [Gabor Grothendieck](https://stat.ethz.ch/pipermail/r-help/2004-June/053343.html) (2004), cf. `list` in the [gsubfn](https://cran.r-project.org/package=gsubfn) package.

If you need specialized forms of "destructured" assignment, I recommend the

[zeallot](https://github.com/nteetor/zeallot) package by [Nate

Teetor](https://github.com/nteetor).

## License

MIT Copyright © 2018 [Eugene Ha](https://github.com/egnha)