「Go言語でつくるインタプリタ」を Rust で移植してみた / "Write An Interpreter In Go" In Rust

RustのLT会 Shinjuku.rs #7 @FORCIA
https://forcia.connpass.com/event/146253/

Transcript

1. ʮGo ݴޠͰͭ͘ΔΠϯλϓϦλʯΛ

   Rust ͰҠ২ͯ͠Έͨ
   ന౔ܛ, Kei Shiratsuchi, @kei_s
   RustͷLTձ Shinjuku.rs #7, 2019.11.19(Tue)
   

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2. ࣗݾ঺հ
   • ന౔ɹܛʢγϥπνɹέΠʣ@kei_s
   • גࣜձࣾϨτϦό
   • ࣗવݴޠॲཧɺԻ੠ೝࣝɺػցֶश
   • ੢৽॓
   • ʮձࣾର߅ͷͲࣗຫେձʯͰ༗໊ͳ৽॓ࡾҪϏϧ
   • Ruby on Rails / JavaScript / Python / Elixir
   • Rust ͸ࠓճॳΊͯ৮ͬͨʢͷͰɺποίϛ׻ܴ…ʣ
   

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3. ϨτϦόηϛφʔ
   • ฐࣾͰ݄Ұճ։࠵͍ͯ͠Δࣾ֎ެ
   ։ηϛφʔ
   • ൃදΛ YouTube Ͱ࿥ը഑৴
   • ࠓճͷ࿩Λ1͔͚࣌ؒͯઆ໌͍ͯ͠
   ΔͷͰɺڵຯ͕͋Ε͹ͪ͜Β΋Ͳ
   ͏ͧ
   • https://www.youtube.com/watch?v=zdq1lUo7b-I
   

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4. ֓ཁ
   

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5. ֓ཁ
   • ʰGo ݴޠͰ࡞ΔΠϯλϓϦλʱ
   • https://www.oreilly.co.jp/books/9784873118222/
   • ΛɺRust Ͱ࠶ݱ͢Δ
   • https://github.com/kei-s/waiir
   • Write An Interpreter In Rust
   • ຊฤɺ෇࿥(ϚΫϩγεςϜ)Λ׬ྃ
   • ίϛοτίϝϯτʹ೔هΛॻ͍ͨ
   

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6. Go ݴޠͰͭ͘ΔΠϯλϓϦλ
   

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7. Go ݴޠͰͭ͘ΔΠϯλϓϦλ
   • ΦϦδφϧͷϓϩάϥϛϯάݴޠͷΠϯλϓϦλΛɺGo ͰΠν͔
   Βͭ͘Δ
   • ֎෦ϥΠϒϥϦΛ࢖༻͠ͳ͍
   • ϓϩάϥϜʢจࣈྻʣ →

   → ࣈ۟ղੳ →ʢτʔΫϯྻʣ→

   → ߏจղੳ →ʢந৅ߏจ໦ʣ→

   → ධՁ →ʢ࣮ߦ݁Ռʣ
   

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8. ࠓճ࡞Δݴޠ “Monkey”
   • Cݴޠ෩ͷߏจ
   • ม਺ଋറ
   • ੔਺ͱਅِ஋
   • ࢉज़ࣜ
   • จࣈྻσʔλܕ
   • ഑ྻσʔλܕ
   • ϋογϡσʔλܕ
   • ؔ਺
   •
   let age = 1;
   let name = "Monkey";
   let result = 10 * (20 / 2);
   let myArray = [1, 2, 3, 4, 5];
   let myHash = {"name": ”Hi", "age": 28};
   myArray[0] // => 1
   myHash["name"] // => ”Hi"
   let add = fn(a, b) { return a + b; };
   let add = fn(a, b) { a + b; };
   add(1, 2);
   

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9. ࠓճ࡞Δݴޠ “Monkey”
   let twice = fn(f, x) { return f(f(x)); };
   let addTwo = fn(x) { return x + 2; };
   twice(addTwo, 2); // => 6
   let fibonacci = fn(x) {
   if (x == 0) {
   0
   } else {
   if (x == 1) {
   1
   } else {
   fibonacci(x - 1) + fibonacci(x - 2);
   }
   }
   };
   • Ϋϩʔδϟ
   • ؔ਺ͷ࠶ؼݺͼग़͠
   • ୈҰڃͷߴ֊ؔ਺
   •
   

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10. σϞ
    • cargo build --release ͯ͠ target/release/waiir Ͱ REPL ىಈ
    • ΋͘͠͸ cargo run
    • ෳ਺ߦΛड͚෇͚ΒΕͳ͍ͷͰ஫ҙ
    •
    

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11. Go ͔Β Rust ΁
    

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12. Go ͔Β Rust ΁
    • ͠ΜͲ͔ͬͨͱ͜Ζ
    2. nil Λฦͤͳ͍
    3. ΠϯλʔϑΣʔε͔Β࣮ମΛऔΕͳ͍
    4. ؀ڥͷॴ༗ݖ
    

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13. nil Λฦͤͳ͍
    • ະ࣮૷ͷτʔΫϯͷॲཧ
    Ͱ nil Λฦͯ͠αϘΕͳ͍
    • Result ͰΤϥʔΛฦ͢
    func (p *Parser) parseStatement() ast.Statement {
    switch p.curToken.Type {
    case token.LET:
    return p.parseLetStatement()
    default:
    return nil
    }
    }
    fn parse_statement(&mut self, cur_token: Token) -> Result {
    Ok(
    match cur_token.t {
    TokenType::Let => Statement::LetStatement(self.parse_let_statement()?),
    _ => return Err(ParseError{message: String::from("not implemented")})
    }
    )
    }
    

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14. ΠϯλʔϑΣʔε͔Β࣮ମΛऔΕͳ͍
    • Go Ͱ͸ΠϯλʔϑΣʔε͔Β࣮ମΛऔΕΔ
    • ast.Expression ͱͯ͠౉͖ͬͯͨ exp Λɺast.Boolean Ͱ͋Δ͔
    νΣοΫ͍ͯ͠Δ
    • Rust ͷ trait Ͱ͸ෆՄೳ
    func testBooleanLiteral(t *testing.T, exp ast.Expression, value bool) bool {
    bo, ok := exp.(*ast.Boolean)
    if !ok {
    t.Errorf("exp not *ast.Boolean. got=%T", exp)
    return false
    }
    …
    

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15. ΠϯλʔϑΣʔε͔Β࣮ମΛऔΕͳ͍
    • Enum ͷྻڍࢠʹ࣮ࡍͷσʔλΛ֨ೲ͠ɺύλʔϯϚο
    νͰ࣮ମΛ࢖͏
    enum Expression {
    Integer(IntegerExpression),
    Boolean(BooleanExpression),
    ...
    }
    #[test]
    fn test_boolean_expressions() {
    ...
    if let Expression::Boolean(boolean) = &stmt.expression {
    assert_eq!(boolean.value, *expected);
    } else {
    assert!(false, "program.statements[0] is not ast::BooleanExpression")
    }
    

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16. ؀ڥͷॴ༗ݖ
    • let a = 1; Λอଘ͢ΔͨΊʹɺΩʔ ”a”ɺ஋ Integer(1) ͱͯ͠อଘ͢Δ
    • ஋Λଋറ͢ΔͨΊͷɺ؀ڥ(Environment)ɻத਎͸ϋογϡϚοϓ
    type Environment struct {
    store map[string]Object
    }
    func (e *Environment) Get(name string) (Object, bool) {
    obj, ok := e.store[name]
    return obj, ok
    }
    func (e *Environment) Set(name string, val Object) Object {
    e.store[name] = val
    return val
    }
    

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17. ؀ڥͷॴ༗ݖ
    • ؔ਺͕ఆٛ͞ΕͨΒɺ؀ڥΛؔ਺ΦϒδΣΫτʹ౉͠
    ͓ͯ͘
    • ࣮ߦ࣌ʹɺͦͷ؀ڥΛݩʹ࣮ߦ͢Δ
    func Eval(node ast.Node, env *object.Environment) object.Object {
    ...
    case *ast.FunctionLiteral:
    params := node.Parameters
    body := node.Body
    return &object.Function{Parameters: params, Env: env, Body: body}
    

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18. ؀ڥͷॴ༗ݖ
    • Rust ൛Ͱ͸࠷ॳɺؔ਺ΦϒδΣΫτ͕࣋ͭ env ͸ clone() ͯ͠౉͍ͯͨ͠
    • ͔͠͠࠶ؼؔ਺ͰΤϥʔ
    • ؔ਺ΦϒδΣΫτ͕࣋ͭ env ʹɺޙ͔Β { “fibonacci”: ؔ਺ΦϒδΣΫτ} Λొ
    ࿥͠ͳ͍ͱ͍͚ͳ͍ͨΊ
    impl_eval!(FunctionLiteral => (self, env) {
    Object::Function(Function {
    parameters: self.parameters.clone(),
    body: *self.body.clone(),
    env: env.clone(),
    })
    });
    let fibonacci = fn(x) {
    ...
    fibonacci(x - 1) + fibonacci(x - 2);
    };
    

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19. ؀ڥͷॴ༗ݖ
    • Rc/RefCell Λ࢖ͬͯղܾ͠
    ͨ
    • ಉҰͷ env Λผʑʹॴ
    ༗ͤ͞ΔͨΊʹ Rc Λ࢖
    ͏
    • Env ΛมߋͰ͖ΔΑ͏
    ʹ RefCell Λ࢖͏
    impl Environment {
    pub fn new() -> Rc> {
    let store = HashMap::new();
    let env = Environment { store, outer: None };
    Rc::new(RefCell::new(env))
    }
    }
    impl_eval!(FunctionLiteral => (self, env) {
    Object::Function(Function {
    parameters: self.parameters.clone(),
    body: *self.body.clone(),
    env: Rc::clone(&env),
    })
    });
    

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20. ·ͱΊ
    

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21. ·ͱΊ
    • Go Ͱ؆୯ʹͰ͖͍ͯͨͱ͜Ζ͕ Rust ͩͱϋϚΔ
    • ͱͯ΋Α͍ Rust ͷษڧʹͳͬͨʂ
    • ίϯύΠϧΤϥʔʹಋ͔ΕͯίʔσΟϯά͢Δײ͡
    

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22. ࠓޙ
    • ஌ࣝෆ଍ͷͨΊɺແବʹ clone() ͯ͠ޡຐԽ͍ͯ͠ΔՕॴ͕͍ͭ͘
    ΋͋Δ…
    • ΍ͬͺΓϥΠϑλΠϜཧղ͠੾Ε͍ͯͳ͍
    • HashMap ʹొ࿥ͨ͠ value ͷॴ༗ݖ೉͍͠
    • ొ࿥ͨ͠ value Λͦͷ··มߋ͍ͨ͠৔߹Ͳ͏͢Ε͹ྑ͍…?
    • Rust తʹ៉ྷʹ͢ΔͱɺGo ͰͷΞʔΩςΫνϟ͔Β͔ͳΓဃ཭
    ͦ͠͏…
    

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