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Merge pull request #15 from moonbitlang/ch5
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,119 @@ | ||
| typealias Name = String | ||
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| enum Ast { | ||
| Var(Name) | ||
| Int(Int) | ||
| Add(Ast, Ast) | ||
| Mul(Ast, Ast) | ||
| Let(Name, Ast, Ast) | ||
| If(Ast, Ast, Ast) | ||
| } derive(Eq, Show) | ||
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| enum Knf { | ||
| Var(Name) | ||
| Int(Int) | ||
| Add(Name, Name) | ||
| Mul(Name, Name) | ||
| Let(Name, Knf, Knf) | ||
| If(Name, Knf, Knf) | ||
| } derive(Eq, Show) | ||
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| pub struct AstToKnfEnv { | ||
| mut counter : Int | ||
| } | ||
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| pub fn AstToKnfEnv::new() -> AstToKnfEnv { | ||
| { counter: 0 } | ||
| } | ||
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| /// Generate a fresh variable name | ||
| fn AstToKnfEnv::fresh(self : AstToKnfEnv) -> Name { | ||
| let name = "x\{self.counter}" | ||
| self.counter += 1 | ||
| name | ||
| } | ||
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| pub fn ast_to_knf(env : AstToKnfEnv, ast : Ast) -> Knf { | ||
| match ast { | ||
| // Trivial cases | ||
| Var(name) => Knf::Var(name) | ||
| Int(i) => Knf::Int(i) | ||
| Add(a, b) => { | ||
| let a_name = env.fresh() | ||
| let b_name = env.fresh() | ||
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| // let a_name = <a> in | ||
| // let b_name = <b> in | ||
| // a_name + b_name | ||
| Knf::Let( | ||
| a_name, | ||
| ast_to_knf(env, a), | ||
| Knf::Let(b_name, ast_to_knf(env, b), Knf::Add(a_name, b_name)), | ||
| ) | ||
| } | ||
| Mul(a, b) => { | ||
| let a_name = env.fresh() | ||
| let b_name = env.fresh() | ||
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| // let a_name = <a> in | ||
| // let b_name = <b> in | ||
| // a_name * b_name | ||
| Knf::Let( | ||
| a_name, | ||
| ast_to_knf(env, a), | ||
| Knf::Let(b_name, ast_to_knf(env, b), Knf::Mul(a_name, b_name)), | ||
| ) | ||
| } | ||
| Let(name, value, body) => | ||
| // let name = <value> in | ||
| // <body> | ||
| Knf::Let(name, ast_to_knf(env, value), ast_to_knf(env, body)) | ||
| If(cond, then, els) => { | ||
| let cond_name = env.fresh() | ||
|
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| // let cond_name = <cond> in | ||
| // if cond_name then <then> else <els> | ||
| Knf::Let( | ||
| cond_name, | ||
| ast_to_knf(env, cond), | ||
| Knf::If(cond_name, ast_to_knf(env, then), ast_to_knf(env, els)), | ||
| ) | ||
| } | ||
| } | ||
| } | ||
|
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| fn main { | ||
| let ast = Ast::Add(Ast::Int(1), Ast::Int(2)) | ||
| let knf = Knf::Let( | ||
| "x0", | ||
| Knf::Int(1), | ||
| Knf::Let("x1", Knf::Int(2), Knf::Add("x0", "x1")), | ||
| ) | ||
| if ast_to_knf(AstToKnfEnv::new(), ast) == knf { | ||
| println("Test passed") | ||
| } else { | ||
| println("Test failed") | ||
| } | ||
|
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||
| // A more complex example | ||
| let ast = Ast::Let( | ||
| "x", | ||
| Ast::Int(1), | ||
| Ast::If( | ||
| Ast::Var("x"), | ||
| Ast::Add(Ast::Var("x"), Ast::Int(2)), | ||
| Ast::Mul(Ast::Var("x"), Ast::Int(2)), | ||
| ), | ||
| ) | ||
| let knf = ast_to_knf(AstToKnfEnv::new(), ast) | ||
| println(knf) | ||
| // Let("x", Int(1), | ||
| // Let("x0", Var("x"), | ||
| // If("x0", | ||
| // Let("x1", Var("x"), | ||
| // Let("x2", Int(2), | ||
| // Add("x1", "x2"))), | ||
| // Let("x3", Var("x"), | ||
| // Let("x4", Int(2), | ||
| // Mul("x3", "x4")))))) | ||
| } |
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