3VTU-5ʙ͍·࢖͏ʂ3VTUʙ ΠϯλϓϦλΛ࡞ͬͯ·ͳͿ 3VTUΒ͍͠ॻ͖ํ !IFMMPZVL

ࣗݾ঺հ ͱΑͩΏ͏͖ αΠόʔΤʔδΣϯτ ΞυςΫελδΦॴଐ ීஈ͸ 4DBMBΤϯδχΞ 3VTU޷͖ ݴޠॲཧܥ޷͖ ฒྻॲཧ޷͖ !IFMMPZVL

ࠓ೔࿩͢͜ͱ ΠϯλϓϦλͱ͸ʁ 3VCZ͔Β 3VTU΁

ΠϯλϓϦλΛ࡞ͬͨ͜ͱͷ͋Δํ !

ιʔείʔυΛղऍͯ͠ந৅ߏจ໦Λ࡞Δ ໦Λղੳ࣮ͯ͠ߦ಺༰ΛධՁ͢Δ ΠϯλϓϦλͱ͸ʁ ۩ମతʹԿΛ͢Δ΋ͷʁ

଍͠ࢉͱֻ͚ࢉɼ਺஋ͷେখൺֱ ܭࢉͷ༏ઌॱҐ͸ߟ͑ͳ͍ ม਺΋ѻ͑Δ ਓྗͰߏจ໦Λ౉͢ɼύʔαʔΛ࡞Βͳ͍ ؆໿ΛԿճ͔ىͯ݁͜͠ՌΛಘΔ ΠϯλϓϦλͱ͸ʁ ࠓճͭ͘ΔΠϯλϓϦλ

ந৅ߏจ໦ʁ !

ΠϯλϓϦλͱ͸ʁ ந৅ߏจ໦ͬͯͲ͏͍͏΋ͷʁ ιʔείʔυΛղऍͯ͠τʔΫϯʹ௚͢ ௚͞ΕͨτʔΫϯ͸໦ߏ଄ʹͳ͍ͬͯΔ

ΠϯλϓϦλͱ͸ʁ ந৅ߏจ໦ͬͯͲ͏͍͏΋ͷʁ

ΠϯλϓϦλͱ͸ʁ ͨͱ͑͹࣮૷͢Δͱ͜Μͳײ͡ Add( Multiply(Number(1), Number(2)), Multiply(Number(3), Number(4)), );

ΠϯλϓϦλͱ͸ʁ ࠓճͭ͘ΔτʔΫϯ ଍͠ࢉ"EE ֻ͚ࢉ.VMUJQMZ ΑΓখ͍͞-FTT5IBO ਺஋/VNCFS ม਺7BS ਅِ஋#PPM7BMVF

؆໿ʁ !

ؔ਺Λద༻ͯ݁͠ՌΛ·ͱΊΔ͜ͱ ׬ྃ৚݅Λຬͨ͢·ͰԿ౓΋؆໿͢Δ ΠϯλϓϦλͱ͸ʁ ؆໿ͱ͸ʁ

؆໿ ؆໿ ؆໿ ΠϯλϓϦλͱ͸ʁ ਺ࣜΛ؆໿ͯ͠ܭࢉ͢Δͱ

ΠϯλϓϦλͱ͸ʁ ࠓճͷαϯϓϧϓϩάϥϜͩͱ // impl Token ͷதͰ͢ pub fn reduce(&self, env: &HashMap) -> 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!"), }, (…)

3VCZ͔Β 3VTU΁

3VCZ͔Β 3VTU΁ 3VCZͷίʔυΛ 3VTUʹ௚ͯ͠ΈΑ͏ ΏΔ;ΘͰ͍͖·͢!

3VCZ͔Β 3VTU΁ 3VCZͷίʔυΛ 3VTUͰॻ͘ͱʜ DMBTTWTFOVN ࠶ؼॲཧͷѻ͍ํ ݁ՌΛҰ࣌อଘ͍ͨ͠ͱ͖

3VTUͷ FOVN ͸୅਺తσʔλܕʹͳͬͯ ͓ΓɼύλʔϯϚονͰ͖Δ 3VCZ͔Β 3VTU΁ DMBTTWTFOVN

ͳͷͰɼ Ͳ͜Λ୅਺తσʔλܕͰ࣮૷Ͱ͖Δ͔Λ·ͣ ߟ͑ΔͱɼεοΩϦ࣮ͨ͠૷ʹͳΓ΍͍͢! 3VCZ͔Β 3VTU΁ DMBTTWTFOVN

3VCZ͔Β 3VTU΁ 3VCZͰ͸ DMBTTͰදݱ͢Δ͕ʜ 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

3VCZ͔Β 3VTU΁ 3VTUͰ͸ FOVN ͰදݱͰ͖Δ #[derive(Clone)] pub enum Token { Number(i32), BoolValue(bool), Var(String), Add(Box, Box), Multiply(Box, Box), LessThan(Box, Box), }

3VCZ͔Β 3VTU΁ 3VCZ͸ؔ਺Λ DMBTTʹॻ͘ class Number < Struct.new(:value) def reducible? false end end class Add < Struct.new(:left, :right) def reducible? true end end (…)

3VCZ͔Β 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, } } }

#PY5 3VCZ͔Β 3VTU΁ ࠶ؼॲཧͷѻ͍ํ

ώʔϓ্ͷσʔλʹର͢ΔϙΠϯλ #PYΛ࢖͏͜ͱͰώʔϓʹσʔλΛอଘ 3VCZ͔Β 3VTU΁ #PY5

3VTU͸ίϯύΠϧ࣌ʹܕͷαΠζΛܾΊΔ ͔͠͠࠶ؼߏ଄͸αΠζ͕ܾ·Βͳ͍ #PYΛ࢖͏ͱαΠζΛܾఆͰ͖Δ 3VCZ͔Β 3VTU΁ ࠶ؼߏ଄ʹ#PY5͕ඞཁͳཧ༝

3VCZ͔Β 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

3VCZ͔Β 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

3VCZ͔Β 3VTU΁ 3VTUͰ͸ #PY5Λ༻͍Δඞཁ͋Γ #[derive(Clone)] pub enum Token { Number(i32), BoolValue(bool), Var(String), Add(Box, Box), Multiply(Box, Box), LessThan(Box, Box), }

NVU TFMG 3VCZ͔Β 3VTU΁ ݁ՌΛҰ࣌อଘ͍ͨ͠ͱ͖

3VCZ͔Β 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

3VCZ͔Β 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) { self.expression = self.expression.reduce(environment); } }

·ͱΊ ୅਺తσʔλܕΛ্खʹ࢖͓͏ ࠶ؼॲཧ΍࠶ؼߏ଄ʹ͸एׯ஫ҙ͕ඞཁ https://github.com/yuk1ty/simple-interpreter-rs ˞3VCZͷίʔυ͸ޙ೔্͛·͢ʂ

3VTU-5ʙ͍·࢖͏ʂ3VTUʙ ͝੩ௌ͋Γ͕ͱ͏͍͟͝·ͨ͠