---
title: 'charr [
]{.content-visible when-format="gfm"}'
format:
html:
theme:
light: flatly
dark: [darkly, darkly-fixes.scss]
gfm:
preview-mode: raw
respect-user-color-scheme: true
format-links: false
vignette: >
%\VignetteIndexEntry{charr}
%\VignetteEngine{quarto::html}
%\VignetteEncoding{UTF-8}
---
::: {.content-visible when-format="gfm"}
:::
**String processing reimagined for ALTREP strings**
`charr` is an experimental fork of `stringr`. The functions and semantics are the same but everything is optimized around ALTREP strings (custom high-performance string storage), allowing for faster and more efficient operation.
`charr` reimplements `stringr`'s API and provides three different backends: the reference implementation from `stringr`, an optimized `base` implementation using ordinary strings, and the default `altrep` implementation that returns ALTREP strings. The three backends are semantically interchangeable.
*This work is supported by the R Consortium Infrastructure Steering Committee, under the grant Universal ALTREP Interoperability for Strings.*
::: {.content-visible when-format="gfm"}
## Installation
Install `charr` from CRAN:
``` r
install.packages("charr")
```
:::
## Benchmark
The figure below compares `charr`'s default setup, the ALTREP backend on a single thread, with the reference backend. It covers thirteen representative operations from across the package, measured on a multilingual [Tatoeba](https://tatoeba.org/) dataset. Each bar is the median of five runs and its length is how many times faster `charr` is than the reference.
::: {.content-visible when-format="gfm"}
:::
::: {.content-visible when-format="html"}
:::
The speedup comes from two things: ALTREP strings avoid much of the overhead of R string storage, and the string operations themselves are rewritten in optimized C++. Most operations can also split their work across threads with `charr_threads()`, which speeds them up further on large inputs.
::: {.content-visible when-format="gfm"}
[Under the hood](https://charbase.github.io/charr/articles/under-the-hood.html) has the complete benchmark record across all `stringr` operations.
:::
::: {.content-visible when-format="html"}
[Under the hood](under-the-hood.html) has the complete benchmark record across all `stringr` operations.
:::
## Choosing a backend
`charr_backend` gets and sets the way strings are processed for all operations. The default is `altrep`:
``` r
charr_backend() # returns current value, default "altrep"
prev <- charr_backend("base") # Optimized functions using ordinary strings
charr_backend("reference") # Original stringr reference
```
Under `altrep`, passing one `charr` call's output into the next keeps the data in ALTREP form the whole way; nothing materializes until something outside `charr` asks for ordinary strings.
The `charr_backend` selection is stored as an option so you can retrieve it with `getOption("charr_backend")`.
## Additional functions
`charr` includes a few functions `stringr` does not have, and more may be added over time.
- `str_reverse()` reverses each string by Unicode code point
- `str_read_lines()` reads a file, converts it to UTF-8, and splits it at Unicode line boundaries. It is the fastest way to get text into `charr`
- `str_write_lines()` writes each string as a line to a file, converting it to the requested encoding. It is the counterpart of `str_read_lines()`
## See also
::: {.content-visible when-format="gfm"}
- [Under the hood](https://charbase.github.io/charr/articles/under-the-hood.html): the three backends, the ICU and C++ choices, and the full per-operation benchmark.
- [Code map](https://charbase.github.io/charr/code-map/): an interactive view of the native source graph, generated from Clang's semantic model.
- [charport](https://charbase.github.io/charport/): the ALTREP string interoperability layer `charr` is built on.
:::
::: {.content-visible when-format="html"}
- [Under the hood](under-the-hood.html): the three backends, the ICU and C++ choices, and the full per-operation benchmark.
- [charport](https://charbase.github.io/charport/): the ALTREP string interoperability layer `charr` is built on.
:::