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|
use crate::r#type::{Type, TypeError, Type::*, TypeError::*, PatFail::*, util::*};
use crate::sexp::{SExp, SExp::*, SLeaf::*, util::*};
use std::collections::{HashMap, HashSet};
use std::iter;
impl SExp {
/// Checks if this expression matches the given type,
/// returns all variable names bound by a respective case.
///
/// Two equal values match:
/// ```rust
/// use myslip::sexp::{SExp::*, SLeaf::*, util::*};
/// use myslip::r#type::{Type::*, util::*, TypeError::*, PatFail::*};
/// assert_eq!(
/// scons(1, scons(2, Nil))
/// .matches_type(&List(vec![Integer, Integer])),
/// Ok(vec![])
/// );
/// ```
///
/// On the other hand, if values don't match, an invalid pattern
/// error should be thrown:
/// ```rust
/// use myslip::sexp::{SExp::*, SLeaf::*, util::*};
/// use myslip::r#type::{Type::*, util::*, TypeError::*, PatFail::*};
/// assert_eq!(
/// scons(1, scons(2, Nil))
/// .matches_type(&List(vec![Integer])),
/// Err(InvalidPattern(TypeMismatch {
/// pattern: scons(1, scons(2, Nil)),
/// expected: List(vec![Integer]),
/// found: List(vec![Integer, Integer])
/// }))
/// );
/// ```
///
/// A wildcard variable matches too and gets the correct type:
/// ```rust
/// use myslip::sexp::{SExp::*, SLeaf::*, util::*};
/// use myslip::r#type::{Type::*, util::*, TypeError::*, PatFail::*};
/// assert_eq!(
/// var("x").matches_type(&List(vec![Integer, Integer])),
/// Ok(vec![("x".to_string(), List(vec![Integer, Integer]))])
/// );
/// ```
///
/// Obviously that should also work for sub-expressions:
/// ```rust
/// use myslip::sexp::{SExp::*, SLeaf::*, util::*};
/// use myslip::r#type::{Type::*, util::*, TypeError::*, PatFail::*};
/// assert_eq!(
/// scons(var("x"), scons(2, Nil)).matches_type(&List(vec![arr(Integer, Integer), Integer])),
/// Ok(vec![("x".to_string(), arr(Integer, Integer))])
/// );
/// ```
///
/// If the wildcard variable is encountered multiple times,
/// an invalid operator error should be returned:
/// ```rust
/// use myslip::sexp::{SExp::*, SLeaf::*, util::*};
/// use myslip::r#type::{Type::*, util::*, TypeError::*, PatFail::*};
/// assert_eq!(
/// scons(var("x"), scons(var("x"), Nil)).matches_type(&List(vec![Integer, Integer])),
/// Err(InvalidPattern(RepeatedVariable(
/// "x".to_string(),
/// scons(var("x"), scons(var("x"), Nil))
/// )))
/// );
/// ```
///
/// Then there's also rest patterns which should be appropriately typed:
/// ```rust
/// use myslip::sexp::{SExp::*, SLeaf::*, util::*};
/// use myslip::r#type::{Type::*, util::*, TypeError::*, PatFail::*};
/// assert_eq!(
/// scons(var("h"), scons(RestPat("t".to_string()), Nil))
/// .matches_type(&List(vec![arr(Integer, Integer), Integer, Integer, Integer])),
/// Ok(vec![
/// ("h".to_string(), arr(Integer, Integer)),
/// ("t".to_string(), List(vec![Integer, Integer, Integer]))
/// ])
/// );
/// ```
///
/// They should also work with vectors:
/// ```rust
/// use myslip::sexp::{SExp::*, SLeaf::*, util::*};
/// use myslip::r#type::{Type::*, util::*, TypeError::*, PatFail::*};
/// assert_eq!(
/// scons(var("h"), scons(RestPat("t".to_string()), Nil))
/// .matches_type(&vecof(Integer)),
/// Ok(vec![
/// ("h".to_string(), Integer),
/// ("t".to_string(), vecof(Integer))
/// ])
/// );
/// ```
///
/// Vector matching should work without the rest pattern too:
/// ```rust
/// use myslip::sexp::{SExp::*, SLeaf::*, util::*};
/// use myslip::r#type::{Type::*, util::*, TypeError::*, PatFail::*};
/// assert_eq!(
/// scons(var("h"), scons(2, Nil)).matches_type(&vecof(Integer)),
/// Ok(vec![("h".to_string(), Integer)])
/// );
/// ```
/// TODO: Nil / empty list
pub fn matches_type(
&self,
ty: &Type
) -> Result<Vec<(String, Type)>, TypeError> {
let mut checks = HashSet::new();
let res = self.clone()
.matches_type_ctx(ty.clone(), HashMap::new())?;
for (k, _) in res.clone() {
if !checks.insert(k.clone()) {
return Err(InvalidPattern(RepeatedVariable(k, self.clone())));
}
}
Ok(res)
}
fn matches_type_ctx(
self,
ty: Type,
ctx: HashMap<String, Type>
) -> Result<Vec<(String, Type)>, TypeError> {
match (self, ty) {
(a, b) if a.infer_list_type(ctx.clone()) == Ok(b.clone()) =>
Ok(ctx.into_iter().collect()),
(a, b) if a.infer_type(ctx.clone()) == Ok(b.clone()) =>
Ok(ctx.into_iter().collect()),
(Atom(Var(name)), t) =>
Ok(ctx.into_iter()
.chain(iter::once((name, t)))
.collect()),
(exp, VecOf(ty)) => {
let mut res: Vec<(String, Type)> =
ctx.clone().into_iter().collect();
let mut exps = exp.clone().parts();
// TODO: Nil or empty exp
let restpat = exps.remove(exps.len() - 1);
for exp in exps {
for et in exp.matches_type_ctx(*ty.clone(), ctx.clone())? {
res.push(et);
}
}
match restpat {
Atom(RestPat(name)) => {
res.push((name, vecof(ty)));
Ok(res)
},
t => {
for et in t.matches_type_ctx(*ty.clone(), ctx.clone())? {
res.push(et);
}
Ok(res)
}
}
},
(SCons(e1, e2), List(typelist)) => {
let explist = scons(e1.clone(), e2.clone()).parts();
let mut res: Vec<(String, Type)> =
ctx.clone().into_iter().collect();
if explist.len() == typelist.len() {
for (exp, ty) in explist.into_iter().zip(typelist) {
for (e, t) in exp.matches_type_ctx(ty, ctx.clone())? {
res.push((e, t));
}
}
Ok(res)
} else {
match explist.last().cloned() {
Some(Atom(RestPat(name))) => {
for (exp, ty) in explist.clone()
.into_iter()
.rev().skip(1).rev()
.zip(typelist.clone())
{
for (e, t) in exp.matches_type_ctx(ty, ctx.clone())? {
res.push((e, t));
}
}
res.push((
name,
List(typelist
.into_iter()
.skip(explist.len() - 1)
.collect())
));
Ok(res)
},
_ => Err(InvalidPattern(TypeMismatch {
pattern: scons(e1.clone(), e2.clone()),
expected: List(typelist),
found: scons(e1, e2).infer_list_type(ctx)?,
})),
}
}
},
(e, t) => {
let found_ty = e.infer_list_type(ctx)?;
Err(InvalidPattern(TypeMismatch {
pattern: e,
expected: t,
found: found_ty
}))
},
}
}
}
|
