From 77cdfc229f56b6d6373ac90f73437b2b39327fde Mon Sep 17 00:00:00 2001
From: Greg Shuflin <greg.shuflin@protonmail.com>
Date: Mon, 25 Oct 2021 20:26:53 -0700
Subject: [PATCH] Basic conditionals working

---
 schala-lang/language/src/reduced_ir/mod.rs    | 31 ++++++++++++++++---
 schala-lang/language/src/reduced_ir/types.rs  |  5 +++
 .../language/src/tree_walk_eval/mod.rs        |  8 +++++
 .../language/src/tree_walk_eval/test.rs       | 14 +++++++--
 4 files changed, 51 insertions(+), 7 deletions(-)

diff --git a/schala-lang/language/src/reduced_ir/mod.rs b/schala-lang/language/src/reduced_ir/mod.rs
index 79a29ec..c203563 100644
--- a/schala-lang/language/src/reduced_ir/mod.rs
+++ b/schala-lang/language/src/reduced_ir/mod.rs
@@ -108,7 +108,7 @@ impl<'a> Reducer<'a> {
         let symbol = self.symbol_table.lookup_symbol(item_id).unwrap();
         let def_id = symbol.def_id().unwrap();
         let function_def = FunctionDefinition {
-            body: self.function(statements)
+            body: self.function_internal_block(statements)
         };
         self.functions.insert(def_id, function_def);
     }
@@ -136,7 +136,7 @@ impl<'a> Reducer<'a> {
             Lambda { params, body, .. } =>  {
                 Expression::Callable(Callable::Lambda {
                     arity: params.len() as u8,
-                    body: self.function(body),
+                    body: self.function_internal_block(body),
                 })
             },
             NamedStruct { .. } => Expression::ReductionError("NamedStruct not implemented".to_string()), //self.reduce_named_struct(name, fields),
@@ -147,8 +147,29 @@ impl<'a> Reducer<'a> {
         }
     }
 
-    fn reduce_if_expression(&mut self, _discriminator: Option<&ast::Expression>, _body: &ast::IfExpressionBody) -> Expression {
-        Expression::ReductionError("if expr".to_string())
+    fn reduce_if_expression(&mut self, discriminator: Option<&ast::Expression>, body: &ast::IfExpressionBody) -> Expression {
+        let cond = Box::new(match discriminator {
+            Some(expr) => self.expression(expr),
+            None => return Expression::ReductionError("blank cond if-expr not supported".to_string()),
+        });
+        match body {
+            ast::IfExpressionBody::SimpleConditional {
+                then_case,
+                else_case,
+            } => {
+                let then_clause = self.function_internal_block(then_case);
+                let else_clause = match else_case.as_ref() {
+                    None => vec![],
+                    Some(stmts) => self.function_internal_block(stmts),
+                };
+                Expression::Conditional {
+                    cond,
+                    then_clause,
+                    else_clause,
+                }
+            },
+            _ => Expression::ReductionError("if expr".to_string())
+        }
     }
 
     fn invocation_argument(&mut self, invoc: &ast::InvocationArgument) -> Expression {
@@ -160,7 +181,7 @@ impl<'a> Reducer<'a> {
         }
     }
 
-    fn function(&mut self, statements: &ast::Block) -> Vec<Statement> {
+    fn function_internal_block(&mut self, statements: &ast::Block) -> Vec<Statement> {
         statements.iter().filter_map(|stmt| self.function_internal_statement(stmt)).collect()
     }
 
diff --git a/schala-lang/language/src/reduced_ir/types.rs b/schala-lang/language/src/reduced_ir/types.rs
index cad89ff..9e0dca7 100644
--- a/schala-lang/language/src/reduced_ir/types.rs
+++ b/schala-lang/language/src/reduced_ir/types.rs
@@ -61,6 +61,11 @@ pub enum Expression {
         f: Box<Expression>,
         args: Vec<Expression>
     },
+    Conditional {
+        cond: Box<Expression>,
+        then_clause: Vec<Statement>,
+        else_clause: Vec<Statement>,
+    },
     ReductionError(String),
 }
 
diff --git a/schala-lang/language/src/tree_walk_eval/mod.rs b/schala-lang/language/src/tree_walk_eval/mod.rs
index 16f0cc7..3d59b9c 100644
--- a/schala-lang/language/src/tree_walk_eval/mod.rs
+++ b/schala-lang/language/src/tree_walk_eval/mod.rs
@@ -262,6 +262,14 @@ impl<'a> State<'a> {
               type_id, tag, items: vec![]
           },
           Expression::Callable(func) => Primitive::Callable(func),
+          Expression::Conditional { box cond, then_clause, else_clause } => {
+              let cond = self.expression(cond)?;
+              match cond {
+                  Primitive::Literal(Literal::Bool(true)) => self.block(then_clause)?,
+                  Primitive::Literal(Literal::Bool(false)) => self.block(else_clause)?,
+                  v => return Err(format!("Non-boolean value {:?} in if-statement", v).into())
+              }
+          },
           Expression::ReductionError(e) => return Err(e.into()),
       })
   }
diff --git a/schala-lang/language/src/tree_walk_eval/test.rs b/schala-lang/language/src/tree_walk_eval/test.rs
index 80e4a9c..6af16a4 100644
--- a/schala-lang/language/src/tree_walk_eval/test.rs
+++ b/schala-lang/language/src/tree_walk_eval/test.rs
@@ -75,9 +75,19 @@ let b = Option::Some(10)
     eval_assert(source, "(Some(10), None)");
 }
 
-/*
+#[test]
+fn basic_if_statement() {
+  let source = r#"
+    let a = 10
+    let b = 10
+    if a == b then { 69 } else { 420 }
+    "#;
+    eval_assert(source, "69");
+}
+
 #[test]
 fn if_is_patterns() {
+/*
   let source = r#"
 type Option<T> = Some(T) | None
 let x = Option::Some(9); if x is Option::Some(q) then { q } else { 0 }"#;
@@ -88,8 +98,8 @@ let x = Option::Some(9); if x is Option::Some(q) then { q } else { 0 }"#;
 type Option<T> = Some(T) | None
 let x = Option::None; if x is Option::Some(q) then { q } else { 0 }"#;
   eval_assert(source, "0");
-}
 */
+}
 
 
 #[test]