change out to a single datum

it can only get, at most, one item per tick, so only represent that.

1 files changed, 4 insertions, 5 deletions

diff --git a/src/forth/vm.rs b/src/forth/vm.rs
index 25ed516..6bab8b9 100644
--- a/src/forth/vm.rs
+++ b/src/forth/vm.rs
@@ -126,7 +126,7 @@ pub struct VM {
     pub wordlist: WordList,
     pub ip: InstructionPointer,
 
-    pub out: Vec<String>,
+    pub out: Option<DataStackType>,
     pub heading: DataStackType,
     pub speed: DataStackType,
     pub doppler: DataStackType,
@@ -153,7 +153,7 @@ impl VM {
             ip: InstructionPointer::new(),
             wordlist,
 
-            out: vec![],
+            out: None,
             heading: 0,
             speed: 0,
             doppler: 0,
@@ -313,7 +313,7 @@ impl VM {
             }
             OpCode::Say => {
                 let v = self.stack.0.pop().ok_or(RuntimeError::StackUnderflow)?;
-                self.out.push(format!("{}", v));
+                let _ = self.out.insert(v);
             }
             OpCode::Heading => {
                 self.stack.0.push(self.heading);
@@ -829,8 +829,7 @@ mod tests {
         let mut vm = VM::new(wordlist);
         vm.run().expect("should run to completion");
         assert_eq!(vm.stack.0.len(), 0, "empty stack");
-        assert_eq!(vm.out.len(), 1, "output length");
-        assert_eq!(vm.out[0], "-1", "output value");
+        assert_eq!(vm.out.expect("output is set"), -1, "output value");
     }
 
     #[test]