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# frozen_string_literal: true
require 'forwardable'
require_relative 'grm_symbol'
module Dendroid
module Syntax
# A sequence of grammar symbols. This class is used to represent
# members of right-hand side of production rules
class SymbolSeq
extend Forwardable
# @return [Array<Dendroid::Syntax::GrmSymbol>] The sequence of symbols
attr_reader :members
def_delegators(:@members, :[], :empty?, :first, :map, :size)
# Create a sequence of grammar symbols (as in right-hand side of
# a production rule).
# @param symbols [Array<Dendroid::Syntax::GrmSymbol>] An array of symbols.
def initialize(symbols)
@members = symbols
end
# @return [String] A text representation of the symbol sequence
def to_s
members.join(' ')
end
# Retrieve all the non-terminal symbols in the sequence.
# @return [Array<Dendroid::Syntax::NonTerminal>] array of non-terminals.
def nonterminals
members.reject(&:terminal?)
end
# Retrieve all the terminal symbols in the sequence.
# @return [Array<Dendroid::Syntax::Terminal>] array of terminals
def terminals
members.select(&:terminal?)
end
# Predicate method to check whether the sequence always derives (matches)
# a non-empty sequence of terminal symbols.
# @return [Boolean]
def productive?
empty? || members.all?(&:productive?)
end
# Equality operator.
# @param other [Dendroid::Syntax::SymbolSeq]
# @return [Boolean] true when members are equal to the ones from `other`
def ==(other)
members == other.members
end
private
def valid_members(symbols)
raise StandardError unless symbols.all? { |symb| symb.is_a?(GrmSymbol) }
end
end # class
end # module
end # module
Version data entries
11 entries across 11 versions & 1 rubygems