Namarara

Namarara is a library that parses boolean expressions, builds an binary expression tree.

Namare can also evalutes a result from a set of values corresponding the variables used within the boolean expression.

binary expression and computes a boolean result from this AST.

Installation

Add this line to your application's Gemfile:

gem 'namarara'

And then execute:

$ bundle

Or install it yourself as:

$ gem install namarara

Usage

Evaluate a single expression

# Initialize Namarara
namarara = Namarara::Parser.new(Namarara::Lexer.new)

# Build the binary expression tree (BET)
namarara_bet = namarara.parse('this AND (that OR other) AND something_else')

# Prepare variables 
variables = {
  this: true,
  that: false,
  other: false,
  something_else: true
}

# Compute tree with variables
result = namarara_bet.compute(variables)

Evaluating a set of rules

# Initialize Namarara
namarara = Namarara::Parser.new(Namarara::Lexer.new)

# A set of rules i want to check
rules = [
    {name: 'vulnerable_person', expr: 'is_adult AND is_subordinate'},
    {name: 'has_constraints', expr: 'is_adult AND has_children' },
    {name: 'is_child', expr: 'NOT is_adult'}
    # ...
]

# A set of values i want to inject (values can come from HTTP or from database
# as long as they are expressed as strings)
namarara.names = {
    "is_adult" => 'false', 
    "is_subordinate" => 'true',
    "has_children" => 'true'
}

rules.map do |rule|
    namarara_bet = namarara.parse(rule)
    result = namarara_bet.compute
    if result then
        warnings << "Rule #{rule} is true"
    end
end

if not warnings.empty?
puts "Attention: vous collectez des DCP de personnes vulnerables"
puts warnings.join("\n")
else
puts "Rien à dire :-)"
end

Development

After checking out the repo, run bin/setup to install dependencies. Then, run rake test 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. To release a new version, update the version number in version.rb, and then run bundle exec rake release, which will create a git tag for the version, push git commits and tags, and push the .gem file to rubygems.org.

Contributing

Bug reports and pull requests are welcome on GitHub at https://github.com/glenux/namarara

License

The gem is available as open source under the terms of the MIT License.

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