Paco
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.
Installation
Add to your Gemfile
:
gem "paco"
And then run bundle install
.
Development
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
.
Contributing
Bug reports and pull requests are welcome on GitHub at https://github.com/skryukov/paco.
Alternatives
- parslet - A small (but featureful) PEG based parser library.
- parsby — Parser combinator library for Ruby inspired by Haskell's Parsec.
License
The gem is available as open source under the terms of the MIT License.