Play with Rubys AST

数学の勉強のために Ruby の構文木と遊んでいる話
2020.02.11. 大江戸 Ruby 会議 08

Transcript

1. ਺ֶͷษڧͷͨΊʹ
   3VCZͷߏจ໦ͱ༡ΜͰ͍Δ࿩
   2020.2.11.
   େߐށRubyձٞ08
   @makicamel
   

   View Slide

2. •@makicamel / ઒ݪສق
   •
   •޷͖ͳ΋ͷ͸Ϗʔϧɹɹͱ͓ञ
   •ࠓ೥ޙ൒ͷ໨ඪ͸਺ֶͷษڧ
   ࣗݾ঺հ
   

   View Slide

3. View Slide

4. View Slide

5. View Slide

6. ࠓ೔͸ 2 ݄ 11 ೔
   

   View Slide

7. View Slide

8. •@makicamel / ઒ݪສق
   •
   •޷͖ͳ΋ͷ͸Ϗʔϧɹɹͱ͓ञ
   •ࠓ೥ޙ൒ͷ໨ඪ͸਺ֶͷษڧ
   ࣗݾ঺հ
   

   View Slide

9. •਺ֶͰͭ·ͮ͘ग़དྷࣄ͕૿͖͑ͯͨ
   •CRuby ࣮૷ͱ͔ Kernel Ϟδϡʔϧ (ΔΓ·) ͱ͔

   ϓϩάϥϛϯάͷجૅ (ຊ) ͱ͔
   •ෳૉ਺ͱ͔ྦྷ৐ͱ͔ 2 ࣍ํఔࣜͱ͔ղͷެࣜͱ͔
   •௥͍ͬͯͨίʔυɾຊ్͕੾Εͯ͠·͏ͷ΋͍ͬͨͳ͍
   •ۤखҙࣝΛࠀ෰ͨ͠Β΋ͬͱָ͘͠ͳΓͦ͏
   ͳͥ਺ֶʁ
   

   View Slide

10. 2 ࣍ํఔࣜ ͷ܎਺ 

    (͍ͣΕ΋࣮਺ͱ͢Δ) Λ༩͑ΒΕͨΒɺ

    ൑ผࣜͷ஋Λฦؔ͢਺ Λ

    σβΠϯϨγϐ※
    ʹ͕ͨͬͯ͠࡞Εɻ

    ͜͜Ͱ ͸ Ͱ͸ͳ͍ͱԾఆͯ͠Α͍ɻ
    ax2 + bx + c = 0 a, b, c
    hanbetsushiki
    a 0
    ϓϩάϥϛϯάͷجૅ $PNQVUFS4DJFODF-JCSBSZ
    
    ୈষؔ਺ͷఆٛcઙҪ݈Ұ

    IUUQTXXXBNB[PODPKQEQ
    ˞σβΠϯϨγϐͱ͸͜ͷຊͰఏএ͞Ε͍ͯΔɺϓϩάϥϜ࡞੒࣌ʹ͕ͨ͠͏΂͖ࢦ਑ͷ͜ͱ
    
    ͨͱ͑͹ʁ
    

    View Slide

11. ɹɹɹɹɹɹɹɹ ͡Όͳͯ͘ɹɹɹɹ ͬͯॻ͖͍ͨ
    ͨͱ͑͹ʁ
    •൑ผࣜ
    •ํఔࣜ ʹରͯ͠ ͷ͜ͱ
    •Ruby Ͱॻ͘ͱ
    •௕͍
    •΋͏গ͠਺ࣜͬΆ͘ॻ͖͍ͨ
    ax2 + bx + c b2 − 4ac
    b ** 2 - 4 * a * c
    4 * a * c 4 a c
    

    View Slide

12. Α͠ɺ࡞Ζ͏
    

    View Slide

13. ࡞ͬͨ ͯΔ
    NBUI@QBSTFSNBLJDBNFMNBUI@QBSTFSc(JU)VC

    IUUQTHJUIVCDPNNBLJDBNFMNBUI@QBSTFS
    

    View Slide

14. ࣮૷ํ਑
    •ͦ΋ͦ΋ɹɹɹɹ ͬͯॻ͘ͱͲ͏ͳΔ͔
    •γϯλοΫεΤϥʔ
    •Ϧςϥϧɾม਺͸ۭനจࣈ۠੾ΓͰฒ΂ΒΕͳ͍※
    •਺஋ͷޙʹ͓͚Δͷ͸ɹɹΈ͍ͨͳԋࢉࢠͳͲ
    4 a c
    ˞BMJBTΩʔϫʔυ΍ه๏ͱ͍ͬͨྫ֎͕͋Γ·͢
    *
    

    View Slide

15. ࣮૷ํ਑
    •ͦ΋ͦ΋ɹɹɹɹ ͬͯॻ͘ͱͲ͏ͳΔ͔
    •γϯλοΫεΤϥʔ
    •Ϧςϥϧɾม਺͸ۭനจࣈ۠੾ΓͰฒ΂ΒΕͳ͍※
    •਺஋ͷޙʹ͓͚Δͷ͸ɹɹΈ͍ͨͳԋࢉࢠͳͲ
    4 a c
    ˞BMJBTΩʔϫʔυ΍ه๏ͱ͍ͬͨྫ֎͕͋Γ·͢
    *
    

    View Slide

16. ࣮૷ํ਑
    Ruby ϓϩάϥϜͷ

    ߏจղੳΛ͢Δ
    

    View Slide

17. ࣮૷ํ਑
    ɹRuby Ͱͭ͘Δ Ruby ͓΋͠Ζ͔ͬͨͰ͢Αʂ
    @neko314_
    

    View Slide

18. Ruby Ͱͭ͘Δ Ruby
    •ԕ౻ (@mame) ͞Μͷஶ࡞
    •ʮRuby Ͱ Ruby Λ࡞Γͳ͕ΒRuby
    ΛֶͿʯຊ
    •Ruby Ͱ Ruby ΠϯλʔϓϦλΛ࡞Δ
    3VCZͰͭ͘Δ3VCZθϩ͔Βֶͼͳ͓͢ϓϩάϥϛϯάݴޠೖ໳cԕ౻ါհ

    IUUQTXXXMBNCEBOPUFDPNQSPEVDUTSVCZSVCZ
    ղઆ΋Θ͔Γ΍ͯ͘͢

    ֆ΋͔Θ͍ͯ͘ͱͯ΋ͨͷ͍͠
    

    View Slide

19. ࣈ۟ղੳ
    ߏจղੳ
    ࣮ߦʢܭࢉʣ
    Ruby Ͱͭ͘Δ Ruby
    

    View Slide

20. ࣈ۟ղੳ
    •ɹɹɹɹɹɹ ͱ͍͏ Ruby ϓϩάϥϜ͸
    4 * a * c
    def hello; "World"; end
    def hello ; “ World " ; end
    ࣈ۟ = Token (τʔΫϯ)
    4 * a * c
    ɹɹͱ͍͏ࣈ۟ʹ෼͚ΒΕΔ
    •ɹɹɹɹɹɹɹɹɹɹɹɹɹɹͱ͍͏ Ruby ϓϩάϥϜ͸
    ɹɹͱ͍͏ࣈ۟ʹ෼͚ΒΕΔ
    

    View Slide

21. ࣈ۟ղੳ
    •ࣈ۟Λղੳͯ͠ҙຯ͚ͮ͢Δ
    •਺஋ɺԋࢉࢠɺจࣈྻɺࣝผࢠͳͲͳͲ
    •ࣈ۟ղੳ = Tokenize (τʔΫφΠζ)
    4 * a * c
    ਺஋ ԋࢉࢠ ԋࢉࢠ
    ࣝผࢠ ࣝผࢠ
    

    View Slide

22. ߏจղੳ
    •ਓ͕ؒɹɹɹ
    4 * a * c
    4 * a * c ΛಡΉ࣌
    

    View Slide

23. ߏจղੳ
    •ΠϯλʔϓϦλ͕ɹɹɹɹɹɹɹΛಡΉ࣌
    4 * a * c
    

    View Slide

24. ߏจղੳ
    •ΠϯλʔϓϦλ͕ɹɹɹɹɹΛಡΉ࣌
    *
    4 * a
    4 * a
    

    View Slide

25. ߏจղੳ
    •ΠϯλʔϓϦλ͕ɹɹɹɹɹɹɹΛಡΉ࣌
    *
    4 *
    a * c
    ൓స
    4 * a * c
    

    View Slide

26. ߏจղੳ
    •ΠϯλʔϓϦλ͕ɹɹɹɹɹɹɹΛಡΉ࣌
    4 * *
    *
    a * c
    ߏจ໦
    4 * a * c
    

    View Slide

27. ߏจղੳ
    •ΠϯλʔϓϦλ͕ɹɹɹɹɹɹɹΛಡΉ࣌
    4 * *
    *
    a * c
    4 * a * c
    •ߏจ໦ʹม׵͢Δ͜ͱ = ߏจղੳ = Parse
    •ղੳͷ్தͰਖ਼͍͠ߏจ͔νΣοΫ͢Δ
    

    View Slide

28. ߏจղੳ
    ͜Μͳߏจ໦͕ಘΒΕͨ࣌ʹɹɹΛೖΕͨΒ͍͚ΔͷͰ͸…ʂʂ
    *
    4
    a
    

    View Slide

29. ࣮૷ํ਑
    •ͦ΋ͦ΋ɹɹɹɹ ͬͯॻ͘ͱͲ͏ͳΔ͔
    •γϯλοΫεΤϥʔ
    •Ϧςϥϧɾม਺͸ۭനจࣈ۠੾ΓͰฒ΂ΒΕͳ͍※
    •਺஋ͷޙʹ͓͚Δͷ͸ɹɹΈ͍ͨͳԋࢉࢠͳͲ
    4 a c
    ˞BMJBTΩʔϫʔυ΍ه๏ͱ͍ͬͨྫ֎͕͋Γ·͢
    *
    

    View Slide

30. ߏจղੳ
    ͜Μͳߏจ໦͕ಘΒΕͨ࣌ʹɹɹΛೖΕͨΒ͍͚ΔͷͰ͸…ʂʂ
    *
    4
    a
    
    ͜Μͳߏจ໦͸ଘࡏ͠ͳ͍
    

    View Slide

31. ߏจղੳ
    •ɹɹɹɹɹɹͱ͍͏τʔΫϯ͕࿈ଓͯ͠ݱΕͨΒ
    ɹɹɹΛૠೖͯ͠ฦ͢
    4 a
    ਺஋ ࣝผࢠ
    *
    

    View Slide

32. Ripper.lex
    TJOHMFUPONFUIPE3JQQFSMFYc3VCZϦϑΝϨϯεϚχϡΞϧ

    IUUQTEPDTSVCZMBOHPSHKBNFUIPE3JQQFSTMFYIUNM
    

    View Slide

33. Ripper.lex
    Ripper.lex('4 * a')
    # => [[[1, 0], :on_int, "4", END],
    # [[1, 1], :on_sp, " ", END],
    # [[1, 2], :on_op, "*", BEG],
    # [[1, 3], :on_sp, " ", BEG],
    # [[1, 4], :on_ident, "a", ARG]]
    Ґஔ৘ใ
    

    View Slide

34. Ripper.lex
    Ripper.lex('4 * a')
    # => [[[1, 0], :on_int, "4", END],
    # [[1, 1], :on_sp, " ", END],
    # [[1, 2], :on_op, "*", BEG],
    # [[1, 3], :on_sp, " ", BEG],
    # [[1, 4], :on_ident, "a", ARG]]
    ੔਺
    ۭനจࣈ
    ԋࢉࢠ
    ࣝผࢠ
    

    View Slide

35. Ripper.lex
    Ripper.lex('4 * a')
    # => [[[1, 0], :on_int, "4", END],
    # [[1, 1], :on_sp, " ", END],
    # [[1, 2], :on_op, "*", BEG],
    # [[1, 3], :on_sp, " ", BEG],
    # [[1, 4], :on_ident, "a", ARG]]
    τʔΫϯจࣈྻ
    

    View Slide

36. Ripper.lex
    Ripper.lex('4 * a')
    # => [[[1, 0], :on_int, "4", END],
    # [[1, 1], :on_sp, " ", END],
    # [[1, 2], :on_op, "*", BEG],
    # [[1, 3], :on_sp, " ", BEG],
    # [[1, 4], :on_ident, "a", ARG]]
    State
    

    View Slide

37. Ripper::Lexer::State
    Ripper::Lexer.constants.select do |constant|
    constant.to_s.start_with? :EXPR.to_s
    end
    # => [
    :EXPR_NONE,
    :EXPR_BEG, :EXPR_END, :EXPR_ENDARG, :EXPR_ENDFN,
    :EXPR_ARG, :EXPR_CMDARG, :EXPR_MID, :EXPR_FNAME,
    :EXPR_DOT, :EXPR_CLASS, :EXPR_LABEL, :EXPR_LABELED,
    :EXPR_FITEM, :EXPR_VALUE,
    :EXPR_BEG_ANY, :EXPR_ARG_ANY, :EXPR_END_ANY
    ]
    •τʔΫϯͷ State
    

    View Slide

38. class RDoc::Parser::RipperStateLex
    class InnerStateLex < Ripper::Filter
    private def on_variables(event, tok, data)
    if @in_fname
    @lex_state = EXPR_ENDFN
    @in_fname = false
    @continue = false
    elsif @continue
    case @lex_state
    when EXPR_DOT
    @lex_state = EXPR_ARG
    else
    @lex_state = EXPR_ENDFN
    @continue = false
    end
    else
    @lex_state = EXPR_CMDARG
    end
    data << Token.new(lineno, column, event, tok, @lex_state)
    end
    # ...
    end
    •ϓϩάϥϜͷͲ͜ʹ͋Δ͔ʹΑͬͯState͕มԽ͢Δ
    

    View Slide

39. ܭࢉͷ࣮ߦ
    def evaluate(tree, genv, lenv)
    case tree[0]
    when "lit"
    tree[1]
    when "+"
    evaluate(tree[1], genv, lenv) + evaluate(tree[2], genv, lenv)
    when "-"
    evaluate(tree[1], genv, lenv) - evaluate(tree[2], genv, lenv)
    when "*"
    evaluate(tree[1], genv, lenv) * evaluate(tree[2], genv, lenv)
    when "/"
    evaluate(tree[1], genv, lenv) / evaluate(tree[2], genv, lenv)
    when "**"
    evaluate(tree[1], genv, lenv)**evaluate(tree[2], genv, lenv)
    when "%"
    evaluate(tree[1], genv, lenv) % evaluate(tree[2], genv, lenv)
    when "evaluate(tree[1], genv, lenv) < evaluate(tree[2], genv, lenv)
    when "<="
    evaluate(tree[1], genv, lenv) <= evaluate(tree[2], genv, lenv)
    when ">"
    # ...
    3VCZͰͭ͘Δ3VCZθϩ͔Βֶͼͳ͓͢ϓϩάϥϛϯάݴޠೖ໳cԕ౻ါհ

    IUUQTXXXMBNCEBOPUFDPNQSPEVDUTSVCZSVCZ
    

    View Slide

40. खॱ
    1. Ripper ʹ͔͚ͯߏจղੳ͕Ͱ͖Δ͔νΣοΫ
    2. Ͱ͖ͳ͚Ε͹਺஋ͱม਺͕ฒΜͰ͍ΔจࣈྻΛ୳͢
    3. ਺஋ͱม਺ͷؒʹ * Λૠೖͯ͠ฦ͢
    4. 1 ʙ 3 ͷ܁Γฦ͠
    5. * ͕ૠೖ͞Εͨߏจ໦Λ࣮ߦ (ܭࢉ) ͢Δ
    ※ ߏจղੳ͸

    Ruby Ͱͭ͘Δ Ruby ͷิॿϥΠϒϥϦ

    minrubyΛ࢖͍·͢
    NJOSVCZNBNFNJOSVCZc(JU)VC

    IUUQTHJUIVCDPNNBNFNJOSVCZ
    

    View Slide

41. खॱ
    1. Ripper ʹ͔͚ͯߏจղੳ͕Ͱ͖Δ͔νΣοΫ
    2. Ͱ͖ͳ͚Ε͹਺஋ͱม਺͕ฒΜͰ͍ΔจࣈྻΛ୳͢
    3. ਺஋ͱม਺ͷؒʹ * Λૠೖͯ͠ฦ͢
    4. 1 ʙ 3 ͷ܁Γฦ͠
    5. * ͕ૠೖ͞Εͨߏจ໦Λ࣮ߦ (ܭࢉ) ͢Δ
    NJOSVCZNBNFNJOSVCZc(JU)VC

    IUUQTHJUIVCDPNNBNFNJOSVCZ
    

    View Slide

42. Ripper.sexp('4 * a')
    # => [:program,
    # [[:binary,
    # [:@int, "4", [1, 0]],
    # :*,
    # [:vcall, [:@ident, "a", [1, 4]]]]]]
    Ripper.sexp
    program͔Β࢝·ΔϦετ
    ೋ෼໦
    ਺஋Ϧςϥϧ
    ৐ࢉԋࢉࢠ
    ࣝผࢠ
    

    View Slide

43. Ripper.sexp('4 a')
    # => nil
    Ripper.sexp
    

    View Slide

44. Ripper.sexp
    class Ripper
    def Ripper.sexp(src, filename = '-', lineno = 1)
    builder = SexpBuilderPP.new(src, filename, lineno)
    sexp = builder.parse
    sexp unless builder.error?
    end
    # ...
    end
    DMBTT3JQQFSSVCZSVCZc(JU)VC

    IUUQTHJUIVCDPNSVCZSVCZCMPCGBCFYUSJQQFSMJCSJQQFSTFYQSC
    

    View Slide

45. ߏจղੳνΣοΫ
    1. Ripper ʹ͔͚ͯߏจղੳ͕Ͱ͖Δ͔νΣοΫ
    module MathParser
    class MathRubyParser < MinRubyParser
    def mathruby_parse(program)
    converted_program = Ripper.sexp(program) ?
    program : reparse(program.strip)
    simplify(Ripper.sexp(converted_program))
    end
    # ...
    end
    end
    

    View Slide

46. τʔΫϯνΣοΫ
    2. Ͱ͖ͳ͚Ε͹਺஋ͱม਺͕ฒΜͰ͍ΔจࣈྻΛ୳͢
    module MathParser::Converter
    def reparse(program)
    tokens = Ripper.lex(program)
    converted_program = convert(tokens)
    original_program = tokens.map{|token| token[2]}.join ""
    program.sub!(original_program, converted_program)
    Ripper.sexp(program).nil? ? reparse(program) : program
    end
    # ...
    end
    

    View Slide

47. module MathParser::Converter
    def convert(tokens)
    lines = []
    tokens.last[0][0].times do |i|
    line_no = i + 1
    previous_numeric = false
    line = []
    tokens.map do |token|
    next if line_no > token[0][0]
    break if line_no < token[0][0]
    if space?(token)
    line << token[2]
    elsif currently_numeric?(token) && previous_numeric
    previous_numeric = true
    line << ["*", token[2]]
    else
    previous_numeric = currently_numeric?(token)
    line << token[2]
    end
    end
    lines << line.join("")
    end
    lines.join("")
    end
    # ...
    end
    ߦ൪߸ͷॳظԽ(1͔Β։࢝)
    ߦ൪߸͕ҧͬͨΒεΩοϓ
    line ʹτʔΫϯΛ௥Ճ
    

    View Slide

48. module MathParser::Converter
    def convert(tokens)
    lines = []
    tokens.last[0][0].times do |i|
    line_no = i + 1
    previous_numeric = false
    line = []
    tokens.map do |token|
    next if line_no > token[0][0]
    break if line_no < token[0][0]
    if space?(token)
    line << token[2]
    elsif currently_numeric?(token) && previous_numeric
    previous_numeric = true
    line << ["*", token[2]]
    else
    previous_numeric = currently_numeric?(token)
    line << token[2]
    end
    end
    lines << line.join("")
    end
    lines.join("")
    end
    # ...
    end
    

    View Slide

49. τʔΫϯνΣοΫ
    2. Ͱ͖ͳ͚Ε͹਺஋ͱม਺͕ฒΜͰ͍ΔจࣈྻΛ୳͢
    module MathParser::Converter
    def currently_numeric?(token)
    ref_variable?(token) || int?(token) ||
    float?(token) || rational?(token)
    end
    def ref_variable?(token)
    (token[1] == :on_ident) &&
    (EXPR_END | EXPR_LABEL) == token[3])
    end
    def int?(token)
    token[1] == :on_int
    end
    # ...
    end
    

    View Slide

50. τʔΫϯνΣοΫ
    2. Ͱ͖ͳ͚Ε͹਺஋ͱม਺͕ฒΜͰ͍ΔจࣈྻΛ୳͢
    module MathParser::Converter
    def currently_numeric?(token)
    ref_variable?(token) || int?(token) ||
    float?(token) || rational?(token)
    end
    def ref_variable?(token)
    (token[1] == :on_ident) &&
    (EXPR_END | EXPR_LABEL) == token[3])
    end
    def int?(token)
    token[1] == :on_int
    end
    # ...
    end
    

    View Slide

51. module MathParser::Converter
    def convert(tokens)
    lines = []
    tokens.last[0][0].times do |i|
    # ...
    tokens.map do |token|
    # ...
    if space?(token)
    line << token[2]
    elsif currently_numeric?(token) && previous_numeric
    previous_numeric = true
    line << ["*", token[2]]
    else
    previous_numeric = currently_numeric?(token)
    line << token[2]
    end
    end
    lines << line.join("")
    end
    # ...
    * ͷૠೖ
    3. ਺஋ͱม਺ͷؒʹ * Λૠೖͯ͠ฦ͢
    

    View Slide

52. 4. 1 ʙ 3 ͷ܁Γฦ͠
    * ͷૠೖ
    module MathParser::Converter
    def reparse(program)
    tokens = Ripper.lex(program)
    converted_program = convert(tokens)
    original_program = tokens.map{|token| token[2]}.join ""
    program.sub!(original_program, converted_program)
    Ripper.sexp(program).nil? ? reparse(program) : program
    end
    # ...
    end
    

    View Slide

53. 4. 1 ʙ 3 ͷ܁Γฦ͠
    Ripper.lex '1 2 3 4 5'
    # => [[[1, 0], :on_int, "1", END],
    # [[1, 1], :on_sp, " ", END],
    # [[1, 2], :on_idt, "2", END]]
    γϯλοΫεΤϥʔʹͳΔͱlex్͕தͰऴྃ͢Δ
    * ͷૠೖ
    program.sub!(original_program, converted_program)
    Ripper.sexp(program).nil? ? reparse(program) : program
    

    View Slide

54. ܭࢉͷ࣮ߦ
    module MathParser
    class MathRubyParser < MinRubyParser
    def mathruby_parse(program)
    converted_program = Ripper.sexp(program) ?
    program : reparse(program.strip)
    simplify(Ripper.sexp(converted_program))
    end
    # ...
    end
    end
    5. * ͕ૠೖ͞Εͨߏจ໦Λ࣮ߦ (ܭࢉ) ͢Δ
    minruby ͷఏڙϝιου

    ߏจ໦Λऔಘͯ͘͠ΕΔ
    

    View Slide

55. ܭࢉͷ࣮ߦ
    5. * ͕ૠೖ͞Εͨߏจ໦Λ࣮ߦ (ܭࢉ) ͢Δ
    module MathParser
    def evaluate(tree, genv, lenv)
    case tree[0]
    when "lit"
    tree[1]
    when "+"
    evaluate(tree[1], genv, lenv) + evaluate(tree[2], genv, lenv)
    when "-"
    evaluate(tree[1], genv, lenv) - evaluate(tree[2], genv, lenv)
    when "*"
    evaluate(tree[1], genv, lenv) * evaluate(tree[2], genv, lenv)
    when "/"
    evaluate(tree[1], genv, lenv) / evaluate(tree[2], genv, lenv)
    when "**"
    evaluate(tree[1], genv, lenv)**evaluate(tree[2], genv, lenv)
    when "%"
    evaluate(tree[1], genv, lenv) % evaluate(tree[2], genv, lenv)
    when "evaluate(tree[1], genv, lenv) < evaluate(tree[2], genv, lenv)
    when "<="
    evaluate(tree[1], genv, lenv) <= evaluate(tree[2], genv, lenv)
    when ">"
    # ...
    3VCZͰͭ͘Δ3VCZθϩ͔Βֶͼͳ͓͢ϓϩάϥϛϯάݴޠೖ໳cԕ౻ါհ

    IUUQTXXXMBNCEBOPUFDPNQSPEVDUTSVCZSVCZ
    evaluate ϝιου͸

    Ruby Ͱͭ͘Δ Ruby ͷ಺༰΄΅ͦͷ··
    

    View Slide

56. ࣮ߦͯ͠ΈΔ
    

    View Slide

57. Ͱ͖ͨʂʂ
    irb(main):001:0> require ‘math_parser'
    => true
    irb(main):002:0' mp '
    irb(main):003:0' a = 2
    irb(main):004:0' c = 3
    irb(main):005:0' 4 a c
    irb(main):006:0> '
    => 24
    

    View Slide

58. irb(main):001:0> require ‘math_parser'
    => true
    irb(main):002:0' mp '
    irb(main):003:0' a = 2
    irb(main):004:0' c = 3
    irb(main):005:0' a 4 c
    irb(main):006:0> '
    Ͱ͖ͯͳ͍
    ϝιουݺͼग़͠ͱͯ͠ղऍ͞ΕΔ
    NoMethodError (undefined method `[]' for nil:NilClass)
    

    View Slide

59. module MathParser
    def evaluate(tree, genv, lenv)
    case tree[0]
    # ...
    when "func_call"
    args = tree[2..].map { |t| evaluate(t, genv, lenv) }
    # ૊ΈࠐΈؔ਺
    if respond_to?(tree[1]) || Kernel.respond_to?(tree[1])
    send(tree[1], *args)
    # Ϣʔβఆٛؔ਺
    elsif genv.has_key? tree[1]
    func_lenv = {}
    mhd = genv[tree[1]]
    params = mhd[1]
    params.each_with_index { |param, j| func_lenv[param] = args[j] }
    evaluate(mhd[2], genv, func_lenv)
    # ະఆٛͷ৔߹͸ tree Λมߋͯ͠࠶౓ evaluate ͢Δ
    else
    new_tree = ["*", ["var_ref", tree[1]], tree[2]]
    evaluate(new_tree, genv, lenv)
    end
    # ...
    end
    end
    end
    5. * ͕ૠೖ͞Εͨߏจ໦Λ࣮ߦ (ܭࢉ) ͢Δ
    Ϣʔβఆٛؔ਺Λొ࿥
    

    View Slide

60. Ͱ͖ͨʂʂ
    irb(main):001:0> require ‘math_parser'
    => true
    irb(main):002:0' mp '
    irb(main):003:0' a = 2
    irb(main):004:0' c = 3
    irb(main):005:0' a 4 c
    irb(main):006:0> '
    => 24
    

    View Slide

61. Ͱ͖ͯͳ͍
    ͪΌΜͱͨ͠ΤϥʔΛ

    ฦ͢Α͏ʹ͍ͨ͠ͳ͋
    ෼਺ͱ͔ྦྷ৐ͱ͔

    ΋ͬͱײ֮తʹ

    ॻ͚ΔΑ͏ʹ͍ͨ͠ͳ͋
    ϝιου಺Ͱ͔͠ม਺

    ͍֮͑ͯΒΕͳ͍
    ͙͢Τϥʔग़Δ
    irb Έ͍ͨͳ REPL ্Ͱ

    ϝιουհͣ͞

    ࣮ߦͰ͖ΔΑ͏ʹ͍ͨ͠
    ●ɹ●
    ָ͠Έ
    

    View Slide

62. ߏจղੳ͸ා͘ͳ͍
    ΊͪΌͪ͘Ό஍ಓ
    Ruby ͍͢͝
    Did you mean? ͍͢͝
    ͍͢͝΋ͷ͍ͬͺ͍͋Δ
    ·ͱΊ
    

    View Slide

63. ࣗ෼Ͱ࢖͏ಓ۩

    ͭ͘Δͷָ͍͠ʂ
    ·ͱΊ
    

    View Slide

64. Special Thanks
    Ruby Ͱͭ͘Δ Ruby | ԕ౻ ါհ (@mame) 

    https://www.lambdanote.com/products/ruby-ruby
    minruby | ԕ౻ ါհ (@mame) 

    https://github.com/mame/minruby
    

    View Slide

65. ͝ਗ਼ௌ͋Γ͕ͱ͏͍͟͝·ͨ͠
    

    View Slide