Loop word

crates/forth/src/vm.rs

@@ -647,6 +647,13 @@ impl Forth {
                     }
                 }
 
+                Op::Loop => {
+                    let beats = stack.pop().ok_or("stack underflow")?.as_float()?;
+                    let dur = beats * 60.0 / ctx.tempo / ctx.speed;
+                    cmd.set_param("fit".into(), dur.to_string());
+                    cmd.set_param("dur".into(), dur.to_string());
+                }
+
                 Op::ListStart => {
                     stack.push(Value::Marker);
                 }