Otherwise the following code:
```
-- count the number of top between two tick
node counting (tick:bool; top:bool)
returns (o: bool);
var v: int;
let o = if tick then v else 0 -> pre o + v;
v = if top then 1 else 0
tel;
```
was involving the following error:
```
Syntax error at <line 1: -- count the number of top between two tick >
```
