Allow endless loops with no condition

src/ast.rs

@@ -101,7 +101,7 @@ pub enum Expression {
 #[derive(Debug, PartialEq, Eq, Clone)]
 pub struct Loop {
     /// The condition that determines if the loop should continue
-    pub condition: Expression,
+    pub condition: Option<Expression>,
     /// This is executed after each loop to advance the condition variables
     pub advancement: Option<Expression>,
     /// The loop body that is executed each loop
@@ -126,12 +126,19 @@ pub struct FunDecl {
     pub body: Rc<BlockScope>,
 }
 
+#[derive(Debug, PartialEq, Eq, Clone)]
+pub struct VarDecl {
+    pub name: Sid,
+    pub var_stackpos: usize,
+    pub rhs: Expression,
+}
+
 #[derive(Debug, PartialEq, Eq, Clone)]
 pub enum Statement {
     Return(Expression),
     Break,
     Continue,
-    Declaration(Sid, usize, Expression),
+    Declaration(VarDecl),
     FunDeclare(FunDecl),
     Expr(Expression),
     Block(BlockScope),

src/astoptimizer.rs

@@ -1,4 +1,4 @@
-use crate::ast::{Ast, BlockScope, Expression, If, Loop, Statement, BinOpType, UnOpType};
+use crate::ast::{Ast, BlockScope, Expression, If, Loop, Statement, BinOpType, UnOpType, VarDecl};
 
 pub trait AstOptimizer {
     fn optimize(ast: Ast) -> Ast;
@@ -24,7 +24,9 @@ impl SimpleAstOptimizer {
                     advancement,
                     body,
                 }) => {
-                    Self::optimize_expr(condition);
+                    if let Some(condition) = condition {
+                        Self::optimize_expr(condition);
+                    }
                     if let Some(advancement) = advancement {
                         Self::optimize_expr(advancement)
                     }
@@ -40,7 +42,7 @@ impl SimpleAstOptimizer {
                     Self::optimize_block(body_false);
                 }
                 Statement::Print(expr) => Self::optimize_expr(expr),
-                Statement::Declaration(_, _, expr) => Self::optimize_expr(expr),
+                Statement::Declaration(VarDecl { name: _, var_stackpos: _, rhs}) => Self::optimize_expr(rhs),
                 Statement::FunDeclare(_) => (),
                 Statement::Return(expr) => Self::optimize_expr(expr),
                 Statement::Break | Statement::Continue => (),

src/interpreter.rs

@@ -155,8 +155,8 @@ impl Interpreter {
                     self.resolve_expr(expr)?;
                 }
 
-                Statement::Declaration(_sid, _idx, rhs) => {
-                    let rhs = self.resolve_expr(rhs)?;
+                Statement::Declaration(decl) => {
+                    let rhs = self.resolve_expr(&decl.rhs)?;
                     self.vartable.push(rhs);
                 }
 
@@ -172,8 +172,10 @@ impl Interpreter {
                 Statement::Loop(looop) => {
                     // loop runs as long condition != 0
                     loop {
-                        if matches!(self.resolve_expr(&looop.condition)?, Value::I64(0)) {
-                            break;
+                        if let Some(condition) = &looop.condition {
+                            if matches!(self.resolve_expr(condition)?, Value::I64(0)) {
+                                break;
+                            }
                         }
 
                         let be = self.run_block(&looop.body)?;

src/parser.rs

@@ -1,7 +1,7 @@
 use thiserror::Error;
 
 use crate::{
-    ast::{Ast, BlockScope, Expression, FunDecl, If, Loop, Statement},
+    ast::{Ast, BlockScope, Expression, FunDecl, If, Loop, Statement, VarDecl},
     stringstore::{Sid, StringStore},
     token::Token,
     util::{PutBackIter, PutBackableExt},
@@ -139,7 +139,7 @@ impl<T: Iterator<Item = Token>> Parser<T> {
             T![return] => {
                 self.next();
                 let stmt = Statement::Return(self.parse_expr()?);
-                
+
                 // After a statement, there must be a semicolon
                 validate_next!(self, T![;], ";");
 
@@ -223,7 +223,11 @@ impl<T: Iterator<Item = Token>> Parser<T> {
                         let sp = self.var_stack.len();
                         self.var_stack.push(sid);
 
-                        Statement::Declaration(sid, sp, rhs)
+                        Statement::Declaration(VarDecl {
+                            name: sid,
+                            var_stackpos: sp,
+                            rhs,
+                        })
                     }
                     (first, _) => {
                         self.putback(first);
@@ -275,27 +279,22 @@ impl<T: Iterator<Item = Token>> Parser<T> {
     fn parse_loop(&mut self) -> ResPE<Loop> {
         validate_next!(self, T![loop], "loop");
 
-        let condition = self.parse_expr()?;
+        let mut condition = None;
         let mut advancement = None;
 
-        let body;
+        if !matches!(self.peek(), T!['{']) {
+            condition = Some(self.parse_expr()?);
 
-        match self.next() {
-            T!['{'] => {
-                body = self.parse_scoped_block()?;
-            }
-
-            T![;] => {
+            if matches!(self.peek(), T![;]) {
+                self.next();
                 advancement = Some(self.parse_expr()?);
-
-                validate_next!(self, T!['{'], "{");
-
-                body = self.parse_scoped_block()?;
             }
-
-            tok => return Err(ParseErr::UnexpectedToken(tok, ";\" or \"{".to_string())),
         }
 
+        validate_next!(self, T!['{'], "{");
+
+        let body = self.parse_scoped_block()?;
+
         validate_next!(self, T!['}'], "}");
 
         Ok(Loop {