Hey, i dont know to name my problem the right way, but i got a problem while using pengines.
This is my whole code so far. You can try it with swish 🙂
```prolog
Create sine table using Pengines
```
My problem now is, that pengine should show “Gaming oder Office” at the beginning and should wait for the response. But for know it just shows it, after i already made an input. It worked before i used that conditional stuff " (Type = ‘Gaming’-\>…; Type=‘Office’ → …)". Is there anything wrong with my prolog code or what is the problem? Trying to solve this now for like 5 hours and cant fix it…
Hope you guys can help me.
---
One suggestion is to simplify the conditional statement under `go` to see if your problem is there. Maybe just:
```prolog
go:-
pengine_input("Gaming oder Office",Type),
(Type = 'Gaming'-> pengine_output('Says gaming'); pengine_output('Says something else')).
```
Good luck!
---
> [@JCR](#):
>
> ```prolog
> go:-
> pengine_input("Gaming oder Office",Type),
> (Type = 'Gaming'-> pengine_output('Says gaming'); pengine_output('Says something else')).
>
> ```
This works well, but if I replace the first output with a new input, it doesn’t work as expected.
So this doesn’t work:
```prolog
go:-
pengine_input("Gaming oder Office",Type),
(Type = 'Gaming'-> pengine_input("Gaming also, welche spiele?", Game1);
Type = 'Office' ->
pengine_output('Says something else')).
```
but I don’t get why?
---
Friendly reminder
=/2 is unification.
==/2 is comparison.
-\>/2 is usually used with comparison and not unification.
I don’t know if that is the cause of your problem but worth remembering and checking. 🙂
---
I get this error in the console. Could this be related to my problem? And how to fix this? 🙂
---
Who knows … If I go to swish and run `?- write(hello).` after enabling the browser debugging tools with network monitoring, I see a pull request with as answer:
```prolog
HTTP/2 200 OK
server: nginx/1.14.0 (Ubuntu)
date: Tue, 18 Jan 2022 15:58:53 GMT
content-type: application/json; charset=UTF-8
content-length: 214
access-control-allow-origin: *
cache-control: no-cache, no-store, must-revalidate
pragma: no-cache
expires: 0
X-Firefox-Spdy: h2
```
That looks fine to me.
---
I tend to write if-then-else patterns in Prolog by splitting different conditions across different clauses because i feel that this is easier to read (not sure if this is the best way though), e.g.
```prolog
go:-
writeln('What food do you like? choose italian, german or mexican.'),
read(Input),
condition(Input).
condition('italian'):-
writeln('Are you vegetarian? yes/no'),
read(Input),
conditionVeg(Input).
condition('german'):- writeln('Knödel it is!').
condition('mexican'):- writeln('Tacos it is!').
conditionVeg('yes'):- writeln('Pizza Margerita it is!').
conditionVeg('no'):- writeln('Vitello Tonnato it is!').
```
Maybe it helps to try something similar 🙂
---
Ok i found a solution by myself now 🤩 .
I changed the pengine object to this:
> var pengine = new Pengine({server: “[https://swish.swi-prolog.org/pengine](https://swish.swi-prolog.org/pengine)”,
> ask:‘go’,
> format:‘json-html’,
> application:‘swish’,
> onprompt:handlePrompt,
> onoutput:handleOutput
> });
> So i added the format option, now the CORS error is gone and it works as expected. Now the prolog messages will also be printed but thats fine, i will just hide them with css or remove them from the DOM with JS.
---