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Start moving eval to explicit continuation based

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This commit is contained in:
Nathan Braswell
2023-05-16 01:15:09 -04:00
parent ea1516fbd1
commit f82101e63f
2 changed files with 50 additions and 30 deletions
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1
kv/.gitignore vendored Normal file
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@@ -0,0 +1 @@
target

79
kv/src/ast.rs
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@@ -1,4 +1,5 @@
use std::fmt; use std::fmt;
use std::boxed::Box;
use std::rc::Rc; use std::rc::Rc;
use std::cell::RefCell; use std::cell::RefCell;
use std::convert::From; use std::convert::From;
@@ -30,6 +31,7 @@ pub enum Form {
PrimComb(String, fn(Rc<Form>, Rc<Form>) -> PossibleTailCall), PrimComb(String, fn(Rc<Form>, Rc<Form>) -> PossibleTailCall),
DeriComb { se: Rc<Form>, de: Option<String>, params: String, body: Rc<Form> }, DeriComb { se: Rc<Form>, de: Option<String>, params: String, body: Rc<Form> },
} }
impl Form { impl Form {
pub fn truthy(&self) -> bool { pub fn truthy(&self) -> bool {
match self { match self {
@@ -106,46 +108,63 @@ impl fmt::Display for Form {
} }
} }
struct Cursor { e: Rc<Form>, f: Rc<Form>, next: Cont }
enum Cont {
ID,
Call { p: Rc<Form>, ne: Rc<Form>, nc: Box<Cont> },
}
pub fn eval(e: Rc<Form>, f: Rc<Form>) -> Rc<Form> { pub fn eval(e: Rc<Form>, f: Rc<Form>) -> Rc<Form> {
let mut e = e; let mut cursor = Cursor { e, f, next: Cont::ID };
let mut x = Option::Some(f);
loop { loop {
let cur = x.take().unwrap(); let Cursor { e, f, mut next } = cursor;
match *cur { if let Form::Pair(ref c, ref p) = *f {
Form::Symbol(ref s) => { cursor = Cursor { e: Rc::clone(&e), f: Rc::clone(c), next: Cont::Call { p: Rc::clone(p), ne: e, nc: Box::new(next) } }
let mut t = e; } else {
let mut v = if let Form::Symbol(ref s) = *f {
let mut t = Rc::clone(&e);
while s != t.car().unwrap().car().unwrap().sym().unwrap() { while s != t.car().unwrap().car().unwrap().sym().unwrap() {
t = t.cdr().unwrap(); t = t.cdr().unwrap();
} }
return t.car().unwrap().cdr().unwrap(); t.car().unwrap().cdr().unwrap()
}, } else {
Form::Pair(ref c, ref p) => { f
let comb = eval(Rc::clone(&e), Rc::clone(c)); };
match *comb { // inner nc popping loop with mutable v?
Form::PrimComb(ref _n, ref f) => match f(e, Rc::clone(p)) { loop {
PossibleTailCall::Result(r) => return r, match next {
PossibleTailCall::TailCall(ne, nx) => { Cont::ID => return v,
e = ne; Cont::Call { p, ne, nc } => {
x = Some(nx); match *v {
}, Form::PrimComb(ref _n, ref f) => match f(ne, p) {
}, PossibleTailCall::Result(r) => {
Form::DeriComb{ref se, ref de, ref params, ref body } => { v = r;
let mut new_e = Rc::clone(se); next = *nc;
if let Some(de) = de { },
new_e = assoc(de, Rc::clone(&e), new_e); PossibleTailCall::TailCall(ne, nf) => {
cursor = Cursor { e: ne, f: nf, next: *nc };
break;
},
},
Form::DeriComb{ref se, ref de, ref params, ref body } => {
let mut new_e = Rc::clone(se);
if let Some(de) = de {
new_e = assoc(de, Rc::clone(&ne), new_e);
}
new_e = assoc(params, p, new_e);
cursor = Cursor { e: new_e, f: Rc::clone(body), next: *nc };
break;
},
_ => panic!("Tried to call not a Prim/DeriComb {:?}", v),
} }
new_e = assoc(params, Rc::clone(p), new_e); }
// always a tail call
e = new_e;
x = Some(Rc::clone(body));
},
_ => panic!("Tried to call not a Prim/DeriComb {:?}", comb),
} }
}, }
_ => return cur,
} }
} }
} }
fn assoc(k: &str, v: Rc<Form>, l: Rc<Form>) -> Rc<Form> { fn assoc(k: &str, v: Rc<Form>, l: Rc<Form>) -> Rc<Form> {
Rc::new(Form::Pair( Rc::new(Form::Pair(
Rc::new(Form::Pair( Rc::new(Form::Pair(