Paco is a parser combinator library inspired by Haskell's Parsec and Parsimmon.
"But I don't need to write another JSON parser or a new language, why do I need your library then?"
Well, most probably you don't. But I can think of rare cases when you do. Say, you need to write a validation for git branch names.
You can go with easy-peasy regex:
branch_name_regex = /^(?!\/|.*(?:[\/.]\.|\/\/|@{|\\|\.lock$|[\/.]$))[^\040\177 ~^:?*\[]+$/
branch_name_regex.match?("feature/branch-validation")
With Paco, you can go with a little more verbose version of that rule:
module BranchNameParser
extend Paco
class << self
def parse(input)
parser.parse(input)
end
def parser
lookahead(none_of("/")).next(valid_chars.join)
end
def valid_chars
any_char.not_followed_by(invalid_sequences).at_least(1)
end
def invalid_sequences
alt(invalid_chars, invalid_endings)
end
def invalid_chars
alt(
string("/."),
string(".."),
string("//"),
string("@{"),
string("\\\\"),
one_of("\040\177 ~^:?*\\[")
)
end
def invalid_endings
seq(
alt(string(".lock"), one_of("/.")),
eof
)
end
end
end
BranchNameParser.parse("feature/branch-validation")
Easy? Not really, but there is a chance you can read it. 😅
See API documentation, examples and specs for more info on usage.
Add to your Gemfile:
And then run bundle install.
After checking out the repo, run bin/setup to install dependencies. Then, run bundle exec rspec to run the tests. You can also run bin/console for an interactive prompt that will allow you to experiment.
To install this gem onto your local machine, run bundle exec rake install.
Bug reports and pull requests are welcome on GitHub at https://github.com/skryukov/paco.
The gem is available as open source under the terms of the MIT License.
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