Rakefile

$:.unshift File.dirname(__FILE__) + '/lib'
require 'ometa'

module Bootstrap
	class BootstrapError < StandardError
	end

	BOOTSTRAP_GRAMMARS = %w[
		null_opt.ometa
		andor_opt.ometa
		ometa_opt.ometa
		bsruby_parser.ometa
		bsruby_translator.ometa
		ometa_parser.ometa
		ometa_translator.ometa
	]

	module_function

	class V0 < Object
	end

	def single root=V0, quiet=false
		puts "bootstrapping ometa using #{root.inspect}" unless quiet
		all = ''

		BOOTSTRAP_GRAMMARS.each do |filename|
			puts "  - #{filename}" unless quiet
			grammar = File.read(File.dirname(__FILE__) + '/ometa/' + filename)
			ast = root.const_get('OMetaParser').matchAllwith(grammar, 'grammar')
			ast = root.const_get('OMetaOptimizer').matchwith(ast, 'optimizeGrammar')
			str = root.const_get('RubyOMetaTranslator').matchwith(ast, 'trans')
			# this hack remains at the moment...
			str.gsub! /initialize/, 'initialize_hook'
			# test its evaluable
			obj = eval(str)
			# that gives us its name
			name = obj.instance_variable_get :@name
			all << "#{name} = " << str << "\n\n"
		end

		all
	end

	# we could also check for AST equivalence, but for now source equivalence will do.
	# note that we create the bootstrapped objects within the Bootstrap module, not as
	# anonymous objects as they refer to each other by name. anonymous module didn't
	# seem to work, but maybe i was doing something wrong...
	def bootstrap
		v1 = single
		eval "module V1; #{v1}; end"
		v2 = single V1
		eval "module V2; #{v2}; end"
		v3 = single V2
		eval "module V3; #{v3}; end"
		raise BootstrapError, 'second and third builds not equivalent' unless v2 == v3
		v3
	end
end

desc 'rebuild bootstrap.rb from the core ometa grammar files'
task :bootstrap do
	# this is kind of like make bootstrap in gcc. the idea is to go through
	# the whole "compilation" of ometa -> rb 3 times, and ensure that the
	# 2nd and 3rd produce the same results. then we replace with our new
	# bootstrap code.
	begin
		str = Bootstrap.bootstrap
	rescue Bootstrap::BootstrapError
		puts "unable to bootstrap - #{$!}"
		exit 1
	end
	puts 'bootstrap successful!'
	open File.dirname(__FILE__) + '/lib/ometa/bootstrap.rb', 'w' do |f|
		f.puts <<-end
#
# this file was automatically generated by `rake bootstrap' at #{Time.now}.
# do not modify
#

		end
		f.puts str
	end
end

desc 'Simple benchmark'
task :bench do
	# all we do is run the complete bootstrap 3 times.
	# this currently takes about 44-48 seconds currently on my laptop (~1.4Ghz single core). 
	# they're pretty simple grammars, so ideally this'd take more like a few seconds...
	# ok after using _x* variant functions which use blocks instead of procs, and removing
	# some other unnecessary procs, we get this down to 30 s. this also has the nice side
	# effect of reducing the size of bootstrap.rb from 13kb down to 10kb.
	# can get it down to 28 with a bit more of that. will now try inlining _or() alternations
	# to avoid the only remaining need for procs. if that doesn't have an appreciable impact,
	# (eg > 5s), i'll revert it and focus on runtime.rb, which is probably where the slowness
	# is - implementation of streams, memoization, the _apply function etc.
	# just tested it on ruby1.9, and the speed was the same.
	t = Time.now
	3.times { Bootstrap.single Bootstrap::V0, true }
	puts "3 bootstraps took #{Time.now - t} seconds"
end