diff options
| -rw-r--r-- | src/sexp/case.rs | 2 | ||||
| -rw-r--r-- | src/sexp/step.rs | 29 |
2 files changed, 30 insertions, 1 deletions
diff --git a/src/sexp/case.rs b/src/sexp/case.rs index 71f5007..d78f7ad 100644 --- a/src/sexp/case.rs +++ b/src/sexp/case.rs @@ -71,7 +71,7 @@ impl SExp { .map(|vs| vs.0.into_iter().chain(vs.1).collect()) }, - _ => todo!(), + _ => None, } } diff --git a/src/sexp/step.rs b/src/sexp/step.rs index fd6be9e..97675fa 100644 --- a/src/sexp/step.rs +++ b/src/sexp/step.rs @@ -349,6 +349,35 @@ impl SExp { None => panic!("unreachable as per match guard arm"), }, + // case expressions + SCons(op, l) if scons(op.clone(), l.clone()).check_case().is_some() => { + let (scrutinee, patarms) = scons(op, l).check_case().unwrap(); + + let scrutinee = match scrutinee { + SCons(q, v) if *q == Atom(Quote) || *q == Atom(Vector) => *v, + t => t, + }; + + for patarm in patarms { + let (pat, arm) = match patarm { + SCons(pat, arm) => Ok((*pat, *arm)), + _ => Err("unreachable after type checking".to_string()) + }?; + let mut arm = match arm { + SCons(x, n) if *n == Atom(Nil) => *x, + t => t, + }; + + if let Some(ctx) = scrutinee.matches_pat(&pat) { + for (name, value) in ctx { + arm = arm.subst(&name, &value); + } + return Ok(arm); + } + } + Err("This should be unreachable after type checking".to_string()) + }, + // op value and a1 .. an values, and b0, b1 .. bn not values // --------------------------------------------------------- |