elixir is a set of tools for transforming R expressions, including
into other programming languages.
Details
One of the neat features of R is that you can use the language to inspect itself. Expressions, functions, indeed entire R scripts can be examined and manipulated just like any list, data.frame, or other R object.
However, the syntax for manipulating R language objects is a little
tricky. Packages such as rlang help to make this task easier. elixir
makes a few extra shortcuts available, and is geared for advanced R
users.
Find and replace for language objects
Sometimes you want to detect certain patterns within an expression or
list of expressions, or easily replace a certain pattern with another.
When working with strings, regular expressions are a handy way of
accomplishing such tasks. elixir provides a sort of "regular
expressions for R expressions" functionality through the functions
expr_match(), expr_replace(), and the "shortcut" functions
expr_count(), expr_detect(), expr_extract(), and expr_locate().
Other elixir features
The function expr_apply() allows you to transform and extract information
from nested list structures which contain expressions, so if you have a big
structure and you want to check all the variable names or make certain
replacements, this may be useful.
expr_sub() offers an interface for extracting or replacing part of an
expression; the one advantage this has over [[ is that it allows you to use
NULL as the index, which gives back the whole expression.
lang2str() does the opposite of base::str2lang(); it is like
deparse1() which is new since R 4.0.0, but with collapse = "" instead of
collapse = " ".
Finally, meld(), translate(), and reindent() are various experimental
functions for constructing code using R.