From cab4702bd61e1b8d7240fb28ad864206ddfb7ec5 Mon Sep 17 00:00:00 2001
From: greg <greg.shuflin@protonmail.com>
Date: Thu, 1 Nov 2018 02:43:47 -0700
Subject: [PATCH] Refactoring matching - WIP

doesn't work yet
---
 schala-lang/language/src/eval.rs        | 79 ++++++++++++-------------
 schala-lang/language/src/reduced_ast.rs | 11 +++-
 2 files changed, 48 insertions(+), 42 deletions(-)

diff --git a/schala-lang/language/src/eval.rs b/schala-lang/language/src/eval.rs
index 0e03199..7bb94ec 100644
--- a/schala-lang/language/src/eval.rs
+++ b/schala-lang/language/src/eval.rs
@@ -369,53 +369,52 @@ impl<'a> State<'a> {
     Ok(Node::Expr(Expr::Unit))
   }
 
-fn case_match_expression(&mut self, cond: Expr, alternatives: Vec<Alternative>) -> EvalResult<Node> {
-  match self.expression(Node::Expr(cond))? {
-    Node::PrimObject { tag, items, .. } => {
-      for alt in alternatives {
-        if alt.tag.map(|t| t == tag).unwrap_or(true) {
-          let mut inner_state = State {
-            values: self.values.new_scope(None),
-            symbol_table_handle: self.symbol_table_handle.clone(),
-          };
-          for (bound_var, val) in alt.bound_vars.iter().zip(items.iter()) {
-            if let Some(bv) = bound_var.as_ref() {
-              inner_state.values.insert(bv.clone(), ValueEntry::Binding { constant: true, val: val.clone() });
-            }
-          }
-
-          if let Some(guard_expr) = alt.guard {
-            let evaled_guard = inner_state.expression(guard_expr.to_node());
-            println!("EVALED GUARD: {:?}", evaled_guard);
-            //continue
-          }
-
-          return inner_state.block(alt.item)
+  fn case_match_expression(&mut self, cond: Expr, alternatives: Vec<Alternative>) -> EvalResult<Node> {
+    let cond = self.expression(Node::Expr(cond))?;
+    for alt in alternatives {
+      // no matter what type of condition we have, ignore alternative if the guard evaluates false
+      if let Some(guard_expr) = alt.guard {
+        let guard_expr = guard_expr.clone().replace_conditional_target_sigil(&cond);
+        match self.expression(guard_expr.to_node())? {
+          Node::Expr(Expr::Lit(::reduced_ast::Lit::Bool(true))) => (),
+          _ => continue,
         }
       }
-      return Err(format!("PrimObject failed pattern match"));
-    },
-    Node::PrimTuple { .. } => Err(format!("Tuples not implemented")), //TODO make a distinction between not yet implemented and an actual runtime error
-    Node::Expr(e) => {
-      for alt in alternatives {
-        match (alt.guard, alt.tag) {
-          (Some(ref guard_expr), None) => {
-            let guard_expr = guard_expr.clone().replace_conditional_target_sigil(&e);
-            match self.expression(guard_expr.to_node())? {
-              Node::Expr(Expr::Lit(::reduced_ast::Lit::Bool(true))) => 
-                return self.block(alt.item),
-              _ => continue,
+
+      match cond {
+        Node::PrimObject { tag, items, .. } => {
+          if alt.tag.map(|t| t == tag).unwrap_or(true) {
+            let mut inner_state = State {
+              values: self.values.new_scope(None),
+              symbol_table_handle: self.symbol_table_handle.clone(),
+            };
+            for (bound_var, val) in alt.bound_vars.iter().zip(items.iter()) {
+              if let Some(bv) = bound_var.as_ref() {
+                inner_state.values.insert(bv.clone(), ValueEntry::Binding { constant: true, val: val.clone() });
+              }
             }
-          },
-          (None, None) => return self.block(alt.item),
-          _ => return Err(format!("Shouldn't match an expr against a pattern"))
+
+            if let Some(guard_expr) = alt.guard {
+              let evaled_guard = inner_state.expression(guard_expr.to_node());
+              println!("EVALED GUARD: {:?}", evaled_guard);
+              //continue
+            }
+
+            return inner_state.block(alt.item)
+          }
+        },
+        Node::PrimTuple { .. } =>  {
+          return Err(format!("Prim tuple not done"))
+        },
+        Node::Expr(e) => {
+          if let None = alt.tag {
+            return self.block(alt.item)
+          }
         }
       }
-      return Err(format!("Expr Failed pattern match"));
     }
-
+    Err(format!("{:?} failed pattern match", cond))
   }
-}
 
   fn value(&mut self, name: Rc<String>) -> EvalResult<Node> {
     use self::ValueEntry::*;
diff --git a/schala-lang/language/src/reduced_ast.rs b/schala-lang/language/src/reduced_ast.rs
index c026a31..112dc43 100644
--- a/schala-lang/language/src/reduced_ast.rs
+++ b/schala-lang/language/src/reduced_ast.rs
@@ -248,8 +248,15 @@ impl Pattern {
           item
         }
       },
-      TuplePattern(_items) => {
-        unimplemented!()
+      TuplePattern(subpatterns) => {
+        let s = handle_symbol(None, subpatterns);
+        Alternative {
+          tag: s.tag,
+          subpatterns: s.subpatterns,
+          guard: s.guard,
+          bound_vars: s.bound_vars,
+          item
+        }
       },
       Record(_name, _pairs) => {
         unimplemented!()