add stack depth

src/Instructions/ExecInstructions.hs

@@ -32,6 +32,9 @@ instructionExecFlush state = instructionFlush state exec
 instructionExecEq :: State -> State
 instructionExecEq state = instructionEq state exec
 
+instructionExecStackDepth :: State -> State
+instructionExecStackDepth state = instructionStackDepth state exec
+
 instructionExecDoRange :: State -> State
 instructionExecDoRange state@(State {_exec = (e1 : es), _int = (i0 : i1 : is)}) =
   if increment i0 i1 /= 0

src/Instructions/FloatInstructions.hs

@@ -71,3 +71,6 @@ instructionFloatFlush state = instructionFlush state float
 
 instructionFloatEq :: State -> State
 instructionFloatEq state = instructionEq state float
+
+instructionFloatStackDepth :: State -> State
+instructionFloatStackDepth state = instructionStackDepth state float

src/Instructions/GenericInstructions.hs

@@ -63,3 +63,6 @@ instructionEq state accessor =
   where
     stackTop :: [a]
     stackTop = take 2 $ view accessor state
+
+instructionStackDepth :: State -> Lens' State [a] -> State
+instructionStackDepth state accessor = state & int .~ (length (view accessor state) : view int state)

src/Instructions/IntInstructions.hs

@@ -76,3 +76,6 @@ instructionIntFlush state = instructionFlush state int
 
 instructionIntEq :: State -> State
 instructionIntEq state = instructionEq state int
+
+instructionIntStackDepth :: State -> State
+instructionIntStackDepth state = instructionStackDepth state int