while!

src/bytecode.rs

@@ -67,8 +67,8 @@ pub enum Instr {
     /// Println the value on top of the stack
     Print,
 
-    /// If the current stack value is true, skip `usize` instructions. When jumping backwards
-    JumpFalse(isize),
-    /// Same as `JumpCond`, but unconditional
+    /// If the current stack value is false, skip `usize` instructions.
+    JmpFalse(isize),
+    /// Same as `JmpFalse`, but unconditional
     Jmp(isize),
 }

src/compile.rs

@@ -163,7 +163,7 @@ impl<'ast, 'bc, 'gc> Compiler<'ast, 'bc, 'gc> {
         self.compile_expr(&if_stmt.cond)?;
 
         // the offset will be fixed later
-        let jmp_idx = self.push_instr(Instr::JumpFalse(0), StackChange::Shrink, if_stmt.span);
+        let jmp_idx = self.push_instr(Instr::JmpFalse(0), StackChange::Shrink, if_stmt.span);
 
         self.compile_block(&if_stmt.body)?;
 
@@ -172,7 +172,7 @@ impl<'ast, 'bc, 'gc> Compiler<'ast, 'bc, 'gc> {
 
             let jmp_pos = self.forward_jmp_offset(jmp_idx as isize);
 
-            self.change_instr(jmp_idx, Instr::JumpFalse(jmp_pos));
+            self.change_instr(jmp_idx, Instr::JmpFalse(jmp_pos));
 
             match else_part {
                 ElsePart::Else(block, _) => {
@@ -188,7 +188,7 @@ impl<'ast, 'bc, 'gc> Compiler<'ast, 'bc, 'gc> {
             self.change_instr(else_skip_jmp_idx, Instr::Jmp(jmp_pos));
         } else {
             let jmp_pos = self.forward_jmp_offset(jmp_idx as isize);
-            self.change_instr(jmp_idx, Instr::JumpFalse(jmp_pos));
+            self.change_instr(jmp_idx, Instr::JmpFalse(jmp_pos));
         }
 
         Ok(())
@@ -222,17 +222,18 @@ impl<'ast, 'bc, 'gc> Compiler<'ast, 'bc, 'gc> {
         let cond_index = self.code_len();
         self.compile_expr(&while_stmt.cond)?;
 
-        let cond_jmp_index = self.push_instr(Instr::Jmp(0), StackChange::Shrink, while_stmt.span);
+        let jmp_false_idx =
+            self.push_instr(Instr::JmpFalse(0), StackChange::Shrink, while_stmt.span);
 
         self.compile_block(&while_stmt.body)?;
 
-        let index_of_jmp = self.code_len();
-        let jmp_offset = -(index_of_jmp - (cond_index as isize) + 1);
+        let jmp_offset = self.back_jmp_offset(cond_index);
         self.push_instr(Instr::Jmp(jmp_offset), StackChange::None, while_stmt.span);
 
-        let skip_amount = self.back_jmp_offset(cond_jmp_index as isize);
-        self.change_instr(cond_jmp_index, Instr::Jmp(skip_amount));
-        todo!()
+        let jmp_offset = self.forward_jmp_offset(jmp_false_idx as isize);
+        self.change_instr(jmp_false_idx, Instr::JmpFalse(jmp_offset));
+
+        Ok(())
     }
 
     fn compile_break(&mut self, _: Span) -> CResult {

src/vm.rs

@@ -151,7 +151,7 @@ impl<'bc> Vm<'bc, '_> {
                 let val = self.stack.pop().unwrap();
                 writeln!(self.stdout, "{}", val).map_err(|_| "failed to write to stdout")?;
             }
-            Instr::JumpFalse(pos) => {
+            Instr::JmpFalse(pos) => {
                 let val = self.stack.pop().unwrap();
                 match val {
                     Value::Bool(false) => self.pc = (self.pc as isize + pos) as usize,

test.dil

@@ -1,3 +1,8 @@
-if 54 > 53 {
-    print "hallo conny";
+let i = 0;
+
+while i < 100 {
+    print i;
+    i = i + 1;
 }
+
+print "done";

tests/control_flow.rs

@@ -78,3 +78,45 @@ if string == "no" {
 }
 "#
 );
+
+run_test!(
+    while_single_loop,
+    r#"
+let x = true;
+while x {
+    x = false;
+    print "iter";
+}
+print "done";
+"#
+);
+
+run_test!(
+    while_count_to_100,
+    r#"
+let i = 0;
+
+while i < 100 {
+    print i;
+    i = i + 1;
+}
+
+print "done";
+    "#
+);
+
+run_test!(
+    while_run_never,
+    r#"
+let not_run = true;
+
+while false {
+    print "WRONG";
+    not_run = false;
+}
+
+if not_run {
+    print "good.";
+}
+"#
+);

tests/snapshots/control_flow__while_count_to_100.snap

@@ -0,0 +1,7 @@
+---
+source: tests/control_flow.rs
+assertion_line: 94
+expression: output
+
+---
+"0\n1\n2\n3\n4\n5\n6\n7\n8\n9\n10\n11\n12\n13\n14\n15\n16\n17\n18\n19\n20\n21\n22\n23\n24\n25\n26\n27\n28\n29\n30\n31\n32\n33\n34\n35\n36\n37\n38\n39\n40\n41\n42\n43\n44\n45\n46\n47\n48\n49\n50\n51\n52\n53\n54\n55\n56\n57\n58\n59\n60\n61\n62\n63\n64\n65\n66\n67\n68\n69\n70\n71\n72\n73\n74\n75\n76\n77\n78\n79\n80\n81\n82\n83\n84\n85\n86\n87\n88\n89\n90\n91\n92\n93\n94\n95\n96\n97\n98\n99\ndone\n"

tests/snapshots/control_flow__while_run_never.snap

@@ -0,0 +1,7 @@
+---
+source: tests/control_flow.rs
+assertion_line: 108
+expression: output
+
+---
+"good.\n"

tests/snapshots/control_flow__while_single_loop.snap

@@ -0,0 +1,7 @@
+---
+source: tests/control_flow.rs
+assertion_line: 82
+expression: output
+
+---
+"iter\ndone\n"