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Tail call optimization in Ruby
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source 'https://rubygems.org' | |
gem "method_source", "~> 0.8.1" |
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GEM | |
remote: https://rubygems.org/ | |
specs: | |
method_source (0.8.1) | |
PLATFORMS | |
ruby | |
DEPENDENCIES | |
method_source (~> 0.8.1) |
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# Tail call optimization | |
# Source: http://jabberwocky.eu/2010/11/23/tail-call-optimization/ | |
# | |
# Usage (on the folder): | |
# | |
# $ bundle install | |
# | |
# $ ruby tail.rb # show stack error | |
# $ XTAIL=true ruby tail.rb # works! | |
begin | |
require "method_source" | |
rescue LoadError => e | |
raise "Run bundle install to install method_source gem" | |
end | |
module Interception | |
RubyVM::InstructionSequence.compile_option = { | |
:tailcall_optimization => true, | |
:trace_instruction => false | |
} | |
# Dirty Dance :P | |
def compile_with_tail(str_method) | |
str_method = %{ | |
class #{self.to_s} | |
#{str_method} | |
end | |
} | |
RubyVM::InstructionSequence.new(str_method).eval | |
end | |
def xtail(method) | |
m = self.instance_method(method) | |
self.send(:undef_method, method) | |
compile_with_tail(m.source) | |
end | |
end | |
class TCOTest | |
extend Interception | |
# tail-recursive factorial | |
compile_with_tail %{ | |
def fact_with_tail( n, acc = 1 ) | |
if n < 2 then acc else fact_with_tail( n-1, n*acc ) end | |
end | |
} | |
def fact( n, acc = 1 ) | |
if n < 2 then acc else fact( n-1, n*acc ) end | |
end | |
xtail(:fact) if ENV['XTAIL'] | |
# length of factorial | |
def fact_size( n ) | |
fact( n ).size | |
rescue | |
$! | |
end | |
end | |
def print_number(gigant_number) | |
puts "#{gigant_number.to_s[0..20]}... " | |
end | |
NUMBER_STACK_EXPLOSION = 10000 | |
begin | |
puts "### fact" | |
print_number TCOTest.new.fact(NUMBER_STACK_EXPLOSION) | |
rescue Exception => e | |
puts e.inspect | |
end | |
puts "### fact_with_tail" | |
print_number TCOTest.new.fact_with_tail(NUMBER_STACK_EXPLOSION) |
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