Talked “Pattern Matching in Ruby” at RubyKaigi 2017. Implemented Toy pattern matching inRuby (After that “Real” pattern matching is introduced by Tsujimoto-san from Ruby2.7, 2019) 3
Know how to see the instructions for YALV (What’s the instructions like?) See The sequence of pattern matching built by the instructions. Try to speed up Pattern Matching of Array pattern 5
… in <pattern> … else … end case / in expression user_ids = [3, 5] case user_ids in [1, 2] :admins in [3, 5] :managers else :other_users end <object> <pattern> <pattern> => “managers”
[1, 2] p “admins” else p “other users” end Hash Pattern response = {status: 404} case response in {status: 404} p “Not Found” else p response end => “Not Found” Array Pattern
included" if user_ids in [*, 1, *] Find Pattern => “admin is included” user = {id: 2, role: "admin"} p "user is admin" if user in {id: 1 } | {role: "admin"} Combine pattern => “user is admin”
ruby code file and get a RubyVM::InstructionSequence instance 2. See the instructions using #disasm iseq = RubyVM::InstructionSequence.compile_ fi le(“path/to/ user_ruby_code.rb“) pp iseq.disasm
matching in rubyʣcommented how it works by ruby code A part of compile.c A part of Tsujimoto-san’s excelent comments if (use_rest_num) { ADD_INSN1(ret, line_node, putobject, INT2FIX(0)); /* allocate stack for rest_num */ ADD_INSN(ret, line_node, swap); if (base_index) { base_index++; } }
case user_ids in [1, 2] :admins en Code obj: [3, 5] <pattern>: [1, 2] Does’nt Pattern have constant || has const and the const eq obj? Does obj have #deconstruct? Does obj#deconstruct return a Array object? The result of obj#deconstruct’s length is equal to Pattern’s one? Check if each element of Pattern === each element of the result of obj#deconstruct Y N Type Error Match Failed N N N N Y Y Y Y Matching Success! If any element is subpattern, instructions will be added recursively
inspecting the object matches Array Pattern. It should return an Array object. (Array returns itself) class Foo def deconstruct [1, 2] end end foo = Foo.new p "Matched!" if foo in [1, 2] => “Matched!” class Array def deconstruct self end end foo = [1, 2] p "Matched!" if foo in [1, 2] => “Matched!”
case res in {status: 200} :success end Code obj: {status: 400} <pattern>: {status: 200} key_args: [:status] Does’nt Pattern have constant or has const and the const eq obj Does obj has #deconstruct_keys(key_args)? Does obj#deconstruct_keys return a Hash object? The result of obj#deconstruct_key’s keys includes all key_args? Check if each element of Pattern matches each element of the result of obj#deconstruct_keys Y N Type Error Match Failed N N N N Y Y Y Y Match Success!
end foo = [1, 2] p "Matched!" if foo in [1, 2] Does’nt Pattern have constant or has const and the const eq obj Does obj has #deconstruct? Does obj#deconstruct return a Array object? The result of obj#deconstruct’s length is equal to Pattern’s one? Check if each element of Pattern === each element of the result of obj#deconstruct Y Y Y Array has #deconstruct by default, and return itself.
and the const eq obj Does obj has #deconstruct? Does obj#deconstruct return a Array object? The result of obj#deconstruct’s length is equal to Pattern’s one? Check if each element of Pattern === each element of the result of obj#deconstruct Y Y Y Are these checks and deconstruction necessary for an object of Array?
Pattern have constant or has const and the const eq obj Does obj has #deconstruct? Does obj#deconstruct return a Array object? The result of obj#deconstruct’s(or value of itself) length is equal to Pattern’s one? Check if each element of Pattern === each element of the result of obj#deconstruct (or value of itself) Y Y Y Y Is Obj an Array? - LABEL *match_failed, *type_error, *deconstruct, *deconstructed; + LABEL *match_failed, *type_error, *deconstruct, *deconstructed, *skip_deconstruct; int i; match_failed = NEW_LABEL(line); type_error = NEW_LABEL(line); deconstruct = NEW_LABEL(line); deconstructed = NEW_LABEL(line); + skip_deconstruct = NEW_LABEL(line); if (use_rest_num) { ADD_INSN1(ret, line_node, putobject, INT2FIX(0)); /* allocate stack for rest_num */ @@ -6439,9 +6440,19 @@ iseq_compile_pattern_each(rb_iseq_t *iseq, LINK_ANCHOR *const ret, const NODE *c CHECK(iseq_compile_pattern_constant(iseq, ret, node, match_failed, in_single_pattern, base_index)); + //skip deconstuct and use obj value when obj is array. + ADD_INSN(ret, line_node, dup); + ADD_INSN1(ret, line_node, checktype, INT2FIX(T_ARRAY)); + ADD_INSNL(ret, line_node, branchif, skip_deconstruct); CHECK(iseq_compile_array_deconstruct(iseq, ret, node, deconstruct, deconstructed, match_failed, type_error, in_single_pattern, base_index, use_deconstructed_cache)); + ADD_LABEL(ret, skip_deconstruct); N diff of compile.c
a Array Does’nt Pattern have constant or has const and the const eq obj Does obj has #deconstruct? Does obj#deconstruct return a Array object? The result of obj#deconstruct’s length is equal to Pattern’s one? Check if each element of Pattern === each element of the result of obj#deconstruct (or value of itself) Y Y Y Y Is Obj an Array? && pattern.length eq obj.length ADD_INSN(ret, line_node, dup); - ADD_INSN1(ret, line_node, checktype, INT2FIX(T_ARRAY)); + ADD_INSN2(ret, line_node, checkpatarray, INT2FIX(min_argc), INT2FIX(apinfo->rest_arg != NULL)); ADD_INSNL(ret, line_node, branchif, skip_deconstruct); CHECK(iseq_compile_array_deconstruct(iseq, ret, node, deconstruct, deconstructed, match_failed, type_error, in_single_pattern, base_index, use_deconstructed_cache)); - ADD_LABEL(ret, skip_deconstruct); - ADD_INSN(ret, line_node, dup); ADD_SEND(ret, line_node, idLength, INT2FIX(0)); @@ -6464,6 +6477,8 @@ iseq_compile_pattern_each(rb_iseq_t *iseq, LINK_ANCHOR *const ret, const NODE *c } ADD_INSNL(ret, line_node, branchunless, match_failed); + ADD_LABEL(ret, skip_deconstruct); + diff of compile.c N
a Array Does’nt Pattern have constant or has const and the const eq obj Does obj has #deconstruct? Does obj#deconstruct return a Array object? The result of obj#deconstruct’s length is equal to Pattern’s one? Check if each element of Pattern === each element of the result of obj#deconstruct (or value of itself) Y Y Y Y Obj is a Array? && pattern.length eq obj.length +DEFINE_INSN +checkpatarray +(rb_num_t length, rb_num_t remain_args) +(VALUE obj) +(VALUE val) +{ + VALUE ary; + + if (RB_TYPE_P(obj, T_ARRAY) && + (remain_args ? (rb_num_t)RARRAY_LEN(obj) >= length : (rb_num_t)RARRAY_LEN(obj) == length)) { + + // TODO: rede fi nition check + val = Qtrue; + } + else { + val = Qfalse; + } +} + diff of insns.def N
x.report{ N.times{ r = obj in [:sym] r = obj in [:sym] r = obj in [:sym] r = obj in [:sym] r = obj in [:sym] } } } user system total real 0.606022 0.000293 0.606315 ( 0.606855) user system total real 0.294262 0.000462 0.294724 ( 0.295170) After Before Achieved twice the speed!!
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![Measurement require 'benchmark' obj = [:sym] N = 1_000_000 Benchmark.bm{|x|](https://files.speakerdeck.com/presentations/ad46a030acdf43d1ab2359db62dba5c6/slide_39.jpg){kind=link}
