Class: Dhaka::ProductionBuilder

Inherits:
Object
  • Object
show all
Defined in:
lib/dhaka/grammar/grammar.rb

Overview

Productions for specific grammar symbols are defined in the context of this class.

Instance Method Summary collapse

Constructor Details

#initialize(grammar, symbol) ⇒ ProductionBuilder

symbol is the grammar symbol that productions are being defined for.



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# File 'lib/dhaka/grammar/grammar.rb', line 10

def initialize(grammar, symbol)
  @grammar = grammar
  @symbol  = symbol
end

Dynamic Method Handling

This class handles dynamic methods through the method_missing method

#method_missing(production_name, expansion, options = {}, &blk) ⇒ Object

Creates a new production for symbol with an expansion of expansion. The options hash can include a directive :prec, the value of which is a grammar symbol name. The precedence of the production is then set to the precedence of the grammar symbol corresponding to that name.

See the arithmetic precedence grammar in the test suites for an example.



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# File 'lib/dhaka/grammar/grammar.rb', line 20

def method_missing(production_name, expansion, options = {}, &blk)
  expansion_symbols = (expansion.respond_to?('lines') ? expansion.lines : expansion).collect {|name| @grammar.symbols[name]}
  production_args   = [@symbol, expansion_symbols, production_name.to_s, blk, @grammar.production_index]
  if precedence_symbol_name = options[:prec] 
    production_args << @grammar.symbol_for_name(precedence_symbol_name).precedence
  end
  
  production = Production.new(*production_args)
  @grammar.production_index += 1
  
  @symbol.nullable = true if expansion_symbols.empty?
  @grammar.productions_by_symbol[production.symbol] << production
  raise "Duplicate production named #{production.name}" if @grammar.productions_by_name[production.name]
  @grammar.productions_by_name[production.name] = production
end