rpn: Fix =: operator pop order for REPL mode

3 files changed, 39 insertions, 4 deletions

diff --git a/internal/repl/repl_test.go b/internal/repl/repl_test.go
index cd062cb..2b7ed16 100644
--- a/internal/repl/repl_test.go
+++ b/internal/repl/repl_test.go
@@ -627,3 +627,39 @@ func TestDefaultExecutorCodePaths(t *testing.T) {
 	// Path 5: Whitespace only (trimmed to empty, returns early)
 	executor("   ")
 }
+
+func TestExecutorWithAssignmentRight(t *testing.T) {
+	// Test := and =: operators
+	executor("5 x :=")
+	state := getRPNState()
+	val, exists := state.vars.GetVariable("x")
+	if !exists {
+		t.Errorf("Variable x should exist after x :=")
+	}
+	if val != 5 {
+		t.Errorf("Variable x = %v, want 5", val)
+	}
+
+	executor("y 3 =:")
+	state = getRPNState()
+	val, exists = state.vars.GetVariable("y")
+	if !exists {
+		t.Errorf("Variable y should exist after y =:")
+	}
+	if val != 3 {
+		t.Errorf("Variable y = %v, want 3", val)
+	}
+}
+
+func TestExecutorWithAssignmentAfterCalculation(t *testing.T) {
+	// Test that assignment works after a calculation
+	executor("1 2 + x =:")
+	state := getRPNState()
+	val, exists := state.vars.GetVariable("x")
+	if !exists {
+		t.Errorf("Variable x should exist")
+	}
+	if val != 3 {
+		t.Errorf("Variable x = %v, want 3", val)
+	}
+}
diff --git a/internal/rpn/operations.go b/internal/rpn/operations.go
index 11aa624..b21e3a9 100644
--- a/internal/rpn/operations.go
+++ b/internal/rpn/operations.go
@@ -990,13 +990,12 @@ func (o *Operations) AssignLeft(stack *Stack) error {
 // Note: When called via the RPN parser, the name is pushed as StringNum.
 // We pop name first (StringNum), then value (Number).
 func (o *Operations) AssignRight(stack *Stack) error {
-	// Pop name first (top of stack), which should be StringNum
+	// Pop name first (top of stack), then value
 	name, err := stack.Pop()
 	if err != nil {
 		return fmt.Errorf("insufficient operands for =: : need variable name")
 	}
 
-	// Pop value (below name on stack)
 	val, err := stack.Pop()
 	if err != nil {
 		return fmt.Errorf("insufficient operands for =: : need value")
diff --git a/internal/rpn/operations_test.go b/internal/rpn/operations_test.go
index e1a9b53..4725f7b 100644
--- a/internal/rpn/operations_test.go
+++ b/internal/rpn/operations_test.go
@@ -1019,7 +1019,7 @@ func TestAssignLeft(t *testing.T) {
 	s := NewStack()
 
 	// For "5 x :=":
-	// Stack should have value (5) on top, name ("x") below
+	// AssignLeft pops val first, then name
 	// Push name first (will be popped second), then value (will be popped first)
 	s.Push(NewStringNum("x"))  // name (will be popped second)
 	s.Push(NewNumber(5, FloatMode))  // value (will be popped first)
@@ -1050,7 +1050,7 @@ func TestAssignRight(t *testing.T) {
 	s := NewStack()
 
 	// For "x 5 =:":
-	// Stack should have name ("x") on top, value (5) below
+	// AssignRight pops name first, then value
 	// Push value first (will be popped second), then name (will be popped first)
 	s.Push(NewNumber(5, FloatMode))  // value (will be popped second)
 	s.Push(NewStringNum("x"))  // name (will be popped first)