tail-position if no longer needs ret

1 files changed, 23 insertions, 11 deletions

diff --git a/src/forth/vm.rs b/src/forth/vm.rs
index 7ce9c03..9c7f203 100644
--- a/src/forth/vm.rs
+++ b/src/forth/vm.rs
@@ -254,6 +254,8 @@ impl VM {
                 } else if let Some(false_clause) = false_clause {
                     self.jmp(false_clause);
                     return Ok(true)
+                } else {
+                    self.ip = self.callstack.0.pop().ok_or(RuntimeError::StackUnderflow)?;
                 }
             },
         }
@@ -501,24 +503,21 @@ mod tests {
 
     #[test]
     fn tail_if_then_false() -> Result<(), RuntimeError> {
-        let mut wordlist = WordList(vec![]);
-        wordlist.0.push(ByteCode(vec![OpCode::Call(1), OpCode::Num(0)]));
-        wordlist.0.push(ByteCode(vec![OpCode::Num(0), OpCode::TIf(2, None), OpCode::Ret]));
-        wordlist.0.push(ByteCode(vec![OpCode::Num(1), OpCode::Ret]));
+        let wordlist = wl_for(vec![
+            vec![OpCode::Call(1), OpCode::Num(0)],
+            vec![OpCode::Num(0), OpCode::TIf(2, None)],
+            vec![OpCode::Num(1), OpCode::Ret],
+        ]);
         let mut vm = VM::new(wordlist);
 
         vm.tick()?;
         assert_eq!(vm.stack.0.len(), 0, "call(1) stack len");
         vm.tick()?;
-        assert_eq!(vm.stack.0.len(), 1, "push 0 stack len");
-        assert_eq!(vm.stack.0[0], 0, "push 0 val");
-        vm.tick()?;
-        assert_eq!(vm.stack.0.len(), 0, "tif stack len");
+        assert_eq!(vm.stack.0, vec![0], "push 0 stack");
         vm.tick()?;
-        assert_eq!(vm.stack.0.len(), 0, "ret stack len");
+        assert_eq!(vm.stack.0, vec![], "tif stack");
         vm.tick()?;
-        assert_eq!(vm.stack.0.len(), 1, "push 0 stack len");
-        assert_eq!(vm.stack.0[0], 0, "push 0 val");
+        assert_eq!(vm.stack.0, vec![0], "push 0 stack");
 
         Ok(())
     }
@@ -599,4 +598,17 @@ mod tests {
         assert_eq!(vm.stack.0, vec![2, 3, 1]);
         Ok(())
     }
+
+    #[test]
+    fn tif_no_ret() -> Result<(), RuntimeError> {
+        let wordlist = wl_for(vec![
+            vec![OpCode::Call(1)],
+            vec![OpCode::Num(0), OpCode::TIf(2, None), OpCode::Num(3)],
+            vec![OpCode::Num(-2)],
+        ]);
+        let mut vm = VM::new(wordlist);
+        vm.run()?;
+        assert_eq!(vm.stack.0, vec![]);
+        Ok(())
+    }
 }