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Convert to more lispish Cons

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greg 2017-12-04 03:23:55 -08:00
parent 46ae176498
commit 2f263de8ba
1 changed files with 15 additions and 22 deletions
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37
src/rukka_lang/mod.rs
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@ -53,13 +53,9 @@ impl EvaluatorState {
SymbolAtom(sym) => unimplemented!(),
expr @ StringAtom(_) => expr,
expr @ NumberAtom(_) => expr,
List(items) => {
if items.len() == 0 {
return Ok(List(items))
}
let ref first = items[0];
match first {
&SymbolAtom(ref sym) => match &sym[..] {
Cons(ref car, ref cdr) => {
match **car {
SymbolAtom(ref sym) => match &sym[..] {
"quote" => unimplemented!(),
"eq?" => unimplemented!(),
"cons" => unimplemented!(),
@ -73,7 +69,8 @@ impl EvaluatorState {
},
_ => unimplemented!()
}
}
},
Nil => Nil,
})
}
}
@ -103,7 +100,8 @@ enum Sexp {
SymbolAtom(String),
StringAtom(String),
NumberAtom(u64),
List(Vec<Sexp>),
Cons(Box<Sexp>, Box<Sexp>),
Nil
}
impl Sexp {
@ -113,15 +111,8 @@ impl Sexp {
&SymbolAtom(ref sym) => format!("{}", sym),
&StringAtom(ref s) => format!("\"{}\"", s),
&NumberAtom(ref n) => format!("{}", n),
&List(ref sexprs) => {
let mut output = String::new();
write!(&mut output, "(").unwrap();
for sexpr in sexprs.iter() {
write!(&mut output, "{}", sexpr.print()).unwrap();
}
write!(&mut output, ")").unwrap();
output
}
&Cons(ref car, ref cdr) => format!("({} . {}", car.print(), cdr.print()),
&Nil => format!("()"),
}
}
}
@ -178,7 +169,7 @@ fn parse(tokens: &mut Peekable<IntoIter<Token>>) -> Result<Sexp, String> {
Some(RParen) => Err(format!("Unexpected ')'")),
Some(Quote) => {
let quoted = parse(tokens)?;
Ok(List(vec![SymbolAtom(format!("quote")), quoted]))
Ok(Cons(Box::new(SymbolAtom(format!("quote"))), Box::new(quoted)))
},
Some(NumLiteral(n)) => Ok(NumberAtom(n)),
None => Err(format!("Unexpected end of input")),
@ -188,14 +179,16 @@ fn parse(tokens: &mut Peekable<IntoIter<Token>>) -> Result<Sexp, String> {
fn parse_sexp(tokens: &mut Peekable<IntoIter<Token>>) -> Result<Sexp, String> {
use self::Token::*;
use self::Sexp::*;
let mut vec = Vec::new();
let mut cell = Nil;
loop {
match tokens.peek() {
None => return Err(format!("Unexpected end of input")),
Some(&RParen) => { tokens.next(); break},
_ => vec.push(parse(tokens)?),
_ => {
cell = Cons(Box::new(parse(tokens)?), Box::new(cell));
}
}
Ok(List(vec))
}
Ok(cell)
}