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Versions: 6
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Contents
# encoding: utf-8
require "set"
module Antelope
module Ace
class Grammar
# Manages precedence for tokens.
module Precedences
# Accesses the generated precedence list. Lazily generates
# the precedence rules on the go, and then caches it.
#
# @return [Array<Ace::Precedence>]
def precedence
@_precedence ||= generate_precedence
end
# Finds a precedence rule for a given token. If no direct
# rule is defined for that token, it will check for a rule
# defined for the special symbol, `:_`. By default, there
# is always a rule defined for `:_`.
#
# @param token [Ace::Token, Symbol]
# @return [Ace::Precedence]
def precedence_for(token)
token = token.name if token.is_a?(Token)
set = Set.new([token, :_])
prec = precedence.
select { |pr| set.intersection(pr.tokens).any? }.
first
if token == :modifier
p prec
end
prec
end
private
# Generates the precedence rules. Loops through the compiler
# given precedence settings, and then adds two default
# precedence rules; one for `:$` (level 0, nonassoc), and one
# for `:_` (level 1, nonassoc).
#
# @return [Array<Ace::Precedence>]
def generate_precedence
size = @compiler.options[:prec].size + 1
precedence = @compiler.options[:prec].
each_with_index.map do |prec, i|
Ace::Precedence.new(prec[0], prec[1..-1].to_set, size - i)
end
precedence <<
Ace::Precedence.new(:nonassoc, [:"$"].to_set, 0) <<
Ace::Precedence.new(:nonassoc, [:_].to_set, 1)
precedence.sort_by { |_| _.level }.reverse
end
end
end
end
end
Version data entries
6 entries across 6 versions & 1 rubygems