cincle
Cincle
This is an old pet project. I keep it for the sake of it. I used it here globoplox/dice.
Cincle is a layer added to the Lingo parser generator. It aim to help to build meaningfull ast by altering the parser, generating a default visitor, and extensibles nodes for each rules.
Installation
dependencies:
cincle:
github: globoplox/cincle
Usage
require "./cincle"
module Expression
include Cincle
node :number {
def val
raw.to_i
end
}
node :operator {
def apply(operands)
operands.reduce { |a,b| plus? ? a + b : a - b }
end
}
node :expression {
def result
operator.apply(numbers.map &.val)
end
}
rule :number { match(/\d+/) }
rule :plus { str("+") }
rule :minus { str("-") }
rule :operator { plus | minus }
rule :expression { number >> operator >> number }
root :expression
end
puts Expression.parse(ARGV[0]).result
Cincle rules are following the same pattern as Lingo (in fact, they are Lingo rules).
The node
macro allow to define a custom body that will be inserted into the classes generated by Cincle. The root
macro must be called after all nodes and rules have been defined.
Onion
The onion
macro can be used to define union:
module Exemple
include Cincle
node :plus {
def apply(a,b)
a + b
end
}
node :minus {
def apply(a,b)
a - b
end
}
rule :plus { str "+" }
rule :minus { str "-" }
onion :operator, [:plus, :minus] {
asbtract def apply
}
root :operator
end
Exemple.parse("-").apply(6,7)
How it works
For each rules, a custom node class will be generated. Each node contain a @nodes
attribute containing all subnodes that have been created during the parsing of the associated rule. E.G. the Expression
node will contain two Numbers
node and an Operator
node. Subnodes can be accessed from the @nodes : Hash(Symbol,Array(Node))
attribute, or from the helpers method <node_name>(index=0)
, <node_name>?(index=0)
and <plural_node_name>
.
The code generated by Cincle can be visualized by adding the --define debug_cincle
to the crystal command.
Todo
- Add a way to make node more typesafe, by removing accessor for nodes that cannot be subnodes of the current node. (E.G.
Number#minus
will raise at compile time, whileOperator#minus
wont). - Add a true pluralizer, and/or allow defining customs pluralizers (trail: DIR constant)
Development
TODO: Write development instructions here
Contributors
- Globoplox Pierre Rousselle - creator, maintainer
cincle
- 1
- 0
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- 1
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- 11 months ago
- March 8, 2019
MIT License
Thu, 07 Nov 2024 20:37:10 GMT