While loops

TODO.md

@@ -1,5 +1,10 @@
 # Immediate TODOs / General Code Cleanup
 
+
+## Evaluator
+
+* Make the evaluator take ReducedIR items by reference
+
 ## Testing
 
 * Make an automatic (macro-based?) system for numbering compiler errors, this should be every type of error

schala-lang/language/src/reduced_ir/mod.rs

@@ -181,7 +181,15 @@ impl<'a, 'b> Reducer<'a, 'b> {
                 Expression::Call { f: Box::new(constructor), args: ordered_args }
             }
             Index { .. } => Expression::ReductionError("Index expr not implemented".to_string()),
-            WhileExpression { .. } => Expression::ReductionError("While expr not implemented".to_string()),
+            WhileExpression { condition, body } => {
+                let cond = Box::new(if let Some(condition) = condition {
+                    self.expression(condition)
+                } else {
+                    Expression::Literal(Literal::Bool(true))
+                });
+                let statements = self.function_internal_block(body);
+                Expression::Loop { cond, statements }
+            }
             ForExpression { .. } => Expression::ReductionError("For expr not implemented".to_string()),
             ListLiteral { .. } => Expression::ReductionError("ListLiteral expr not implemented".to_string()),
             Access { name, expr } =>
@@ -271,6 +279,7 @@ impl<'a, 'b> Reducer<'a, 'b> {
     }
 
     fn prefix(&mut self, prefix: &ast::PrefixOp, arg: &ast::Expression) -> Expression {
+        println!("PREFIX: {:?} and ARG: {:?}", prefix, arg);
         let builtin: Option<Builtin> = TryFrom::try_from(prefix).ok();
         match builtin {
             Some(op) => Expression::Call {

schala-lang/language/src/reduced_ir/types.rs

@@ -58,6 +58,7 @@ pub enum Expression {
     Call { f: Box<Expression>, args: Vec<Expression> },
     Conditional { cond: Box<Expression>, then_clause: Vec<Statement>, else_clause: Vec<Statement> },
     CaseMatch { cond: Box<Expression>, alternatives: Vec<Alternative> },
+    Loop { cond: Box<Expression>, statements: Vec<Statement> },
     ReductionError(String),
 }
 

schala-lang/language/src/tree_walk_eval/evaluator.rs

@@ -16,15 +16,22 @@ enum StatementOutput {
     Nothing,
 }
 
+#[derive(Debug, Clone, Copy)]
+enum LoopControlFlow {
+    Break,
+    Continue,
+}
+
 pub struct Evaluator<'a, 'b> {
     type_context: &'b TypeContext,
     state: &'b mut State<'a>,
     early_returning: bool,
+    loop_control: Option<LoopControlFlow>,
 }
 
 impl<'a, 'b> Evaluator<'a, 'b> {
     pub(crate) fn new(state: &'b mut State<'a>, type_context: &'b TypeContext) -> Self {
-        Self { state, type_context, early_returning: false }
+        Self { state, type_context, early_returning: false, loop_control: None }
     }
 
     pub fn evaluate(&mut self, reduced: ReducedIR, repl: bool) -> Vec<Result<String, String>> {
@@ -61,12 +68,14 @@ impl<'a, 'b> Evaluator<'a, 'b> {
             if self.early_returning {
                 break;
             }
+            if let Some(_) = self.loop_control {
+                break;
+            }
         }
         Ok(if let Some(ret) = retval { ret } else { self.expression(Expression::unit())? })
     }
 
     fn statement(&mut self, stmt: Statement) -> EvalResult<StatementOutput> {
-        println!("Statement: {:?}", stmt);
         match stmt {
             Statement::Binding { ref id, expr, constant: _ } => {
                 let evaluated = self.expression(expr)?;
@@ -82,8 +91,14 @@ impl<'a, 'b> Evaluator<'a, 'b> {
                 self.early_returning = true;
                 Ok(StatementOutput::Primitive(evaluated))
             }
-            Statement::Break => unimplemented!(),
-            Statement::Continue => unimplemented!(),
+            Statement::Break => {
+                self.loop_control = Some(LoopControlFlow::Break);
+                Ok(StatementOutput::Nothing)
+            }
+            Statement::Continue => {
+                self.loop_control = Some(LoopControlFlow::Continue);
+                Ok(StatementOutput::Nothing)
+            }
         }
     }
 
@@ -150,6 +165,7 @@ impl<'a, 'b> Evaluator<'a, 'b> {
             }
             Expression::CaseMatch { box cond, alternatives } =>
                 self.case_match_expression(cond, alternatives)?,
+            Expression::Loop { box cond, statements } => self.loop_expression(cond, statements)?,
             Expression::ReductionError(e) => return Err(e.into()),
             Expression::Access { name, box expr } => {
                 let expr = self.expression(expr)?;
@@ -176,6 +192,37 @@ impl<'a, 'b> Evaluator<'a, 'b> {
         })
     }
 
+    fn loop_expression(&mut self, cond: Expression, statements: Vec<Statement>) -> EvalResult<Primitive> {
+        let existing = self.loop_control;
+        let output = self.loop_expression_inner(cond, statements);
+        self.loop_control = existing;
+        output
+    }
+
+    fn loop_expression_inner(
+        &mut self,
+        cond: Expression,
+        statements: Vec<Statement>,
+    ) -> EvalResult<Primitive> {
+        loop {
+            let cond = self.expression(cond.clone())?;
+            match cond {
+                Primitive::Literal(Literal::Bool(true)) => (),
+                Primitive::Literal(Literal::Bool(false)) => break,
+                e => return Err(format!("Loop condition evaluates to non-boolean: {:?}", e).into()),
+            };
+            //TODO eventually loops shoudl be able to return something
+            let _output = self.block(statements.clone())?;
+            match self.loop_control {
+                None | Some(LoopControlFlow::Continue) => (),
+                Some(LoopControlFlow::Break) => {
+                    break;
+                }
+            }
+        }
+        Ok(Primitive::unit())
+    }
+
     fn case_match_expression(
         &mut self,
         cond: Expression,

schala-lang/language/src/tree_walk_eval/test.rs

@@ -412,5 +412,19 @@ let z = marbuk(5, 6)
 (x, y, z)
     "#;
     eval_assert(source, "((100, 100), (5, 2), (50, 50))");
-
+}
+
+#[test]
+fn loops() {
+    let source = r#"
+let mut a = 0
+let mut count = 0
+while !(a == 5) {
+    a = a + 1
+    count = count + 100
+}
+
+count
+    "#;
+    eval_assert(source, "500");
 }