From 4193971303d54947c3c797cd27ad285b9c5dcaeb Mon Sep 17 00:00:00 2001
From: Greg Shuflin <greg.shuflin@protonmail.com>
Date: Sun, 24 Oct 2021 18:59:00 -0700
Subject: [PATCH] Handle lambdas in reduced IR

---
 schala-lang/language/src/reduced_ir/mod.rs    |  7 ++-
 schala-lang/language/src/reduced_ir/types.rs  |  6 ++-
 .../language/src/tree_walk_eval/mod.rs        | 53 +++++++++++--------
 3 files changed, 42 insertions(+), 24 deletions(-)

diff --git a/schala-lang/language/src/reduced_ir/mod.rs b/schala-lang/language/src/reduced_ir/mod.rs
index 9fa1bfd..e8e5740 100644
--- a/schala-lang/language/src/reduced_ir/mod.rs
+++ b/schala-lang/language/src/reduced_ir/mod.rs
@@ -130,7 +130,12 @@ impl<'a> Reducer<'a> {
                 discriminator,
                 body,
             } => Unimplemented, //self.reduce_if_expression(deref_optional_box(discriminator), body),
-            Lambda { params, body, .. } => Unimplemented, //self.reduce_lambda(params, body),
+            Lambda { params, body, .. } =>  {
+                Expression::Callable(Function::Lambda {
+                    arity: params.len() as u8,
+                    body: self.function(body),
+                })
+            },
             NamedStruct { name, fields } => Unimplemented, //self.reduce_named_struct(name, fields),
             Index { .. } => Unimplemented,
             WhileExpression { .. } => Unimplemented,
diff --git a/schala-lang/language/src/reduced_ir/types.rs b/schala-lang/language/src/reduced_ir/types.rs
index d2af782..273f174 100644
--- a/schala-lang/language/src/reduced_ir/types.rs
+++ b/schala-lang/language/src/reduced_ir/types.rs
@@ -80,7 +80,11 @@ pub struct FunctionDefinition {
 #[derive(Debug, Clone)]
 pub enum Function {
     Builtin(Builtin),
-    UserDefined(DefId)
+    UserDefined(DefId),
+    Lambda {
+        arity: u8,
+        body: Vec<Statement>
+    }
 }
 
 #[derive(Debug, Clone)]
diff --git a/schala-lang/language/src/tree_walk_eval/mod.rs b/schala-lang/language/src/tree_walk_eval/mod.rs
index 2114189..fbcdd3b 100644
--- a/schala-lang/language/src/tree_walk_eval/mod.rs
+++ b/schala-lang/language/src/tree_walk_eval/mod.rs
@@ -246,7 +246,23 @@ impl<'a> State<'a> {
       };
       match func {
           Function::Builtin(builtin) => self.apply_builtin(builtin, args),
-          Function::UserDefined(def_id) => self.apply_function(def_id, args),
+          Function::UserDefined(def_id) => {
+              let mem = (&def_id).into();
+              match self.environments.lookup(&mem) {
+                  Some(RuntimeValue::Function(FunctionDefinition { body })) => {
+                      let body = body.clone(); //TODO ideally this clone would not happen
+                      self.apply_function(body, args)
+                  },
+                  e => Err(format!("Error looking up function with id {}: {:?}", def_id, e))
+              }
+          },
+          Function::Lambda { arity, body } => {
+              if arity as usize != args.len() {
+                  return Err(format!("Lambda expression requries {} arguments, only {} provided", arity, args.len()));
+              }
+              let body = body.clone(); //TODO again ideally, no cloning here
+              self.apply_function(body, args)
+          }
       }
   }
 
@@ -331,31 +347,24 @@ impl<'a> State<'a> {
       })
   }
 
-  fn apply_function(&mut self, def_id: DefId, args: Vec<Expression>) -> EvalResult<Primitive> {
-      let mem = (&def_id).into();
-      Ok(match self.environments.lookup(&mem) {
-          Some(RuntimeValue::Function(FunctionDefinition { body })) => {
-              let body = body.clone(); //TODO ideally this clone would not happen
+  fn apply_function(&mut self, body: Vec<Statement>, args: Vec<Expression>) -> EvalResult<Primitive> {
 
-              let mut evaluated_args: Vec<Primitive> = vec![];
-              for arg in args.into_iter() {
-                  evaluated_args.push(self.expression(arg)?);
-              }
+      let mut evaluated_args: Vec<Primitive> = vec![];
+      for arg in args.into_iter() {
+          evaluated_args.push(self.expression(arg)?);
+      }
 
-              let mut frame_state = State {
-                  environments: self.environments.new_scope(None)
-              };
+      let mut frame_state = State {
+          environments: self.environments.new_scope(None)
+      };
 
-              for (n, evaled) in evaluated_args.into_iter().enumerate() {
-                  let n = n as u8;
-                  let mem = n.into();
-                  frame_state.environments.insert(mem, RuntimeValue::Primitive(evaled));
-              }
+      for (n, evaled) in evaluated_args.into_iter().enumerate() {
+          let n = n as u8;
+          let mem = n.into();
+          frame_state.environments.insert(mem, RuntimeValue::Primitive(evaled));
+      }
 
-              frame_state.block(body)?
-          },
-          e => return Err(format!("Error looking up function with id {}: {:?}", def_id, e)),
-      })
+      frame_state.block(body)
   }
 }