インタプリタを作ってまなぶ Rust らしい書き方

Rust LT#2 発表用資料です．「Rust らしい」というと少しおこがましいですが，他の言語から Rust に入ってこられた方向けに少し考えてみました．

本日使用したコード例はこちら→https://github.com/yuk1ty/simple-interpreter-rs

Transcript

1. 3VTU
   -5
   
   ʙ͍·࢖͏ʂ3VTUʙ ΠϯλϓϦλΛ࡞ͬͯ·ͳͿ 3VTU
   Β͍͠ॻ͖ํ !IFMMPZVL
2. ࣗݾ঺հ ͱΑͩΏ͏͖  αΠόʔΤʔδΣϯτ  ΞυςΫελδΦॴଐ  ීஈ͸ 4DBMB
   ΤϯδχΞ  3VTU
   ޷͖  ݴޠॲཧܥ޷͖  ฒྻॲཧ޷͖ !IFMMPZVL
3. ࠓ೔࿩͢͜ͱ  ΠϯλϓϦλͱ͸ʁ  3VCZ
   ͔Β 3VTU
   ΁
4. ΠϯλϓϦλΛ࡞ͬͨ͜ͱͷ͋Δํ !
5.  ιʔείʔυΛղऍͯ͠ந৅ߏจ໦Λ࡞Δ  ໦Λղੳ࣮ͯ͠ߦ಺༰ΛධՁ͢Δ ΠϯλϓϦλͱ͸ʁ ۩ମతʹԿΛ͢Δ΋ͷʁ
6.  ଍͠ࢉͱֻ͚ࢉɼ਺஋ͷେখൺֱ  ܭࢉͷ༏ઌॱҐ͸ߟ͑ͳ͍  ม਺΋ѻ͑Δ  ਓྗͰߏจ໦Λ౉͢ɼύʔαʔΛ࡞Βͳ͍  ؆໿ΛԿճ͔ىͯ݁͜͠ՌΛಘΔ ΠϯλϓϦλͱ͸ʁ ࠓճͭ͘ΔΠϯλϓϦλ
7. ந৅ߏจ໦ʁ !
8. ΠϯλϓϦλͱ͸ʁ ந৅ߏจ໦ͬͯͲ͏͍͏΋ͷʁ  ιʔείʔυΛղऍͯ͠τʔΫϯʹ௚͢  ௚͞ΕͨτʔΫϯ͸໦ߏ଄ʹͳ͍ͬͯΔ
9. ΠϯλϓϦλͱ͸ʁ ந৅ߏจ໦ͬͯͲ͏͍͏΋ͷʁ 
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
10. ΠϯλϓϦλͱ͸ʁ ͨͱ͑͹࣮૷͢Δͱ͜Μͳײ͡ Add( Multiply(Number(1), Number(2)), Multiply(Number(3), Number(4)), );
11. ΠϯλϓϦλͱ͸ʁ ࠓճͭ͘ΔτʔΫϯ  ଍͠ࢉ
    "EE  ֻ͚ࢉ
    .VMUJQMZ  ΑΓখ͍͞
    -FTT5IBO  ਺஋
    /VNCFS  ม਺
    7BS  ਅِ஋
    #PPM7BMVF
12. ؆໿ʁ !
13.  ؔ਺Λద༻ͯ݁͠ՌΛ·ͱΊΔ͜ͱ  ׬ྃ৚݅Λຬͨ͢·ͰԿ౓΋؆໿͢Δ ΠϯλϓϦλͱ͸ʁ ؆໿ͱ͸ʁ
14. 
    
    
    
    
    
     ؆໿ 
    
    
    
    
    
     ؆໿ 
    
    
    
    
     ؆໿  ΠϯλϓϦλͱ͸ʁ ਺ࣜΛ؆໿ͯ͠ܭࢉ͢Δͱ
15. ΠϯλϓϦλͱ͸ʁ ࠓճͷαϯϓϧϓϩάϥϜͩͱ // impl Token ͷதͰ͢ pub fn reduce(&self, env: &HashMap<String, Token>) -> Token { use Token::*; match self { (…) &Add(ref blv, ref brv) if blv.is_reducible() => { Add(Box::new(blv.reduce(env)), brv.clone()) } &Add(ref blv, ref brv) if brv.is_reducible() => { Add(blv.clone(), Box::new(brv.reduce(env))) } &Add(ref blv, ref brv) => match **blv { Number(left_value) => match **brv { Number(right_value) => Number(left_value + right_value), _ => panic!("Unexpected error in Add!"), }, _ => panic!("Unexpected error in Add!"), }, (…)
16. 3VCZ
    ͔Β 3VTU
    ΁
17. 3VCZ
    ͔Β 3VTU
    ΁ 3VCZ
    ͷίʔυΛ 3VTU
    ʹ௚ͯ͠ΈΑ͏ ΏΔ;ΘͰ͍͖·͢!
18. 3VCZ
    ͔Β 3VTU
    ΁ 3VCZ
    ͷίʔυΛ 3VTU
    Ͱॻ͘ͱʜ 
    DMBTT
    WT
    FOVN 
    ࠶ؼॲཧͷѻ͍ํ 
    ݁ՌΛҰ࣌อଘ͍ͨ͠ͱ͖
19. 3VTU
    ͷ FOVN ͸୅਺తσʔλܕʹͳͬͯ ͓ΓɼύλʔϯϚονͰ͖Δ 3VCZ
    ͔Β 3VTU
    ΁ DMBTT
    WT
    FOVN
20. ͳͷͰɼ Ͳ͜Λ୅਺తσʔλܕͰ࣮૷Ͱ͖Δ͔Λ·ͣ ߟ͑ΔͱɼεοΩϦ࣮ͨ͠૷ʹͳΓ΍͍͢! 3VCZ
    ͔Β 3VTU
    ΁ DMBTT
    WT
    FOVN
21. 3VCZ
    ͔Β 3VTU
    ΁ 3VCZ
    Ͱ͸ DMBTT
    Ͱදݱ͢Δ͕ʜ class Number < Struct.new(:value) end class Var < Struct.new(:value) end class Add < Struct.new(:left, :right) end class Multiply < Struct.new(:left, :right) end class LessThan < Struct.new(:left, :right) end class BoolValue < Struct.new(:bool) end
22. 3VCZ
    ͔Β 3VTU
    ΁ 3VTU
    Ͱ͸ FOVN ͰදݱͰ͖Δ #[derive(Clone)] pub enum Token { Number(i32), BoolValue(bool), Var(String), Add(Box<Token>, Box<Token>), Multiply(Box<Token>, Box<Token>), LessThan(Box<Token>, Box<Token>), }
23. 3VCZ
    ͔Β 3VTU
    ΁ 3VCZ
    ͸ؔ਺Λ DMBTT
    ʹॻ͘ class Number < Struct.new(:value) def reducible? false end end class Add < Struct.new(:left, :right) def reducible? true end end (…)
24. 3VCZ
    ͔Β 3VTU
    ΁ 3VTU
    ͸ύλʔϯϚον͕࢖͑Δ impl Token { pub fn is_reducible(&self) -> bool { use Token::*; match *self { Number(_) => false, BoolValue(_) => false, Var(_) => true, Add(_, _) => true, Multiply(_, _) => true, LessThan(_, _) => true, } } }
25. #PY5 3VCZ
    ͔Β 3VTU
    ΁ ࠶ؼॲཧͷѻ͍ํ
26.  ώʔϓ্ͷσʔλʹର͢ΔϙΠϯλ  #PY
    Λ࢖͏͜ͱͰώʔϓʹσʔλΛอଘ 3VCZ
    ͔Β 3VTU
    ΁ #PY5
27.  3VTU
    ͸ίϯύΠϧ࣌ʹܕͷαΠζΛܾΊΔ  ͔͠͠࠶ؼߏ଄͸αΠζ͕ܾ·Βͳ͍  #PY
    Λ࢖͏ͱαΠζΛܾఆͰ͖Δ 3VCZ
    ͔Β 3VTU
    ΁ ࠶ؼߏ଄ʹ#PY5͕ඞཁͳཧ༝
28. 3VCZ
    ͔Β 3VTU
    ΁ ଟ͘ͷݴޠͰ͸࠶ىߏ଄΋ී௨ʹѻ͑Δ class Number < Struct.new(:value) end class Var < Struct.new(:value) end class Add < Struct.new(:left, :right) end class Multiply < Struct.new(:left, :right) end class LessThan < Struct.new(:left, :right) end class BoolValue < Struct.new(:bool) end
29. 3VCZ
    ͔Β 3VTU
    ΁ ଟ͘ͷݴޠͰ͸࠶ىߏ଄΋ී௨ʹѻ͑Δ class Number < Struct.new(:value) end class Var < Struct.new(:value) end class Add < Struct.new(:left, :right) end class Multiply < Struct.new(:left, :right) end class LessThan < Struct.new(:left, :right) end class BoolValue < Struct.new(:bool) end ࣮ߦ͔ͯ͠Β ελοΫΦʔόʔϑϩʔͨ͠Γ͢Δ
30. 3VCZ
    ͔Β 3VTU
    ΁ 3VTU
    Ͱ͸ #PY5
    Λ༻͍Δඞཁ͋Γ #[derive(Clone)] pub enum Token { Number(i32), BoolValue(bool), Var(String), Add(Box<Token>, Box<Token>), Multiply(Box<Token>, Box<Token>), LessThan(Box<Token>, Box<Token>), }
31. NVU TFMG 3VCZ
    ͔Β 3VTU
    ΁ ݁ՌΛҰ࣌อଘ͍ͨ͠ͱ͖
32. 3VCZ
    ͔Β 3VTU
    ΁ ঢ়ଶͷอଘॲཧ͸Ͳ͏ͨ͠Βʜ class Machine < Struct.new(:expression) def step self.expression = expression.reduce end def run while expression.reducible? puts expression step end puts expression end end
33. 3VCZ
    ͔Β 3VTU
    ΁ NVU Λ࢖ͬͯ௚ͯ͠ΈΔ impl Machine { (…) pub fn run(&mut self) { let environment = HashMap::new(); while self.expression.is_reducible() { println!("{}", &self.expression); self.step(&environment); } println!("{}", &self.expression); } fn step(&mut self, environment: &HashMap<String, Token>) { self.expression = self.expression.reduce(environment); } }
34. ·ͱΊ  ୅਺తσʔλܕΛ্खʹ࢖͓͏  ࠶ؼॲཧ΍࠶ؼߏ଄ʹ͸एׯ஫ҙ͕ඞཁ https://github.com/yuk1ty/simple-interpreter-rs ˞
    3VCZ
    ͷίʔυ͸ޙ೔্͛·͢ʂ
35. 3VTU
    -5
    
    ʙ͍·࢖͏ʂ3VTUʙ ͝੩ௌ͋Γ͕ͱ͏͍͟͝·ͨ͠