Regular expressions are very powerful feature, however they are often difficult to interpret. Rex allows you to build complex regular expressions from human readable expressions. So instead of writing (and later trying to decipher)
r <- "^(?:(((?:[^:])+)://))?((?:(?:(?!:/).)*)+)(?:(:([[:digit:]]+)))?(?:(/.*))?$"
You can write
r <- rex(
start,
## match the protocol -- may exist or may not
maybe(capture(
capture(except_some_of(":")),
"://"
)),
## match the path
capture(one_or_more(not(":/"))),
## get the port
maybe(capture(":", capture(numbers))),
## and the rest
maybe(capture("/", anything)),
end
)
While these expressions are a bit longer than their corresponding regular expression, they are much more readable and maintainable.
The vignettes have longer form usage examples.
Each rex() function call can include a number of functions and shortcuts. For a full list of the functions available please see ?rex and ?shortcuts.
Rex functions are not exported because they are only useful within rex() calls, but they can be temporarily attached using rex_mode() which allows them to be auto-completed.
Using rex in other packages will generate spurious NOTEs from R CMD check unless you include a call to rex::register_shortcuts() with your package name somewhere in your package source. This function registers all of the rex shortcuts as valid variables fixing the NOTEs.
rex.rex regular expressions use.RetroSearch is an open source project built by @garambo | Open a GitHub Issue
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