When I compile this code I get "stack overflow" printed in the console. Anyone know why?

---
int fact(int X)() {
	if(X == 0) {
		return 1;
	} else {
		int temp = fact!(X - 1)();
		return X * temp;
	}
}

const someVar = fact!(0)();
---

On Sun, 24 May 2009 20:49:53 -0300, Ary Borenszweig wrote:

> When I compile this code I get "stack overflow" printed in the console. Anyone know why?
> 
> ---
> int fact(int X)() {
> 	if(X == 0) {
> 		return 1;
> 	} else {
> 		int temp = fact!(X - 1)();
> 		return X * temp;
> 	}
> }
> 
> const someVar = fact!(0)();
> ---

Because you generate fact!(-1)(), fact!(-2)() and so on at compile time.
You recursive template doesn't terminate.

Ary Borenszweig wrote:
> When I compile this code I get "stack overflow" printed in the console. Anyone know why?
> 
> ---
> int fact(int X)() {
>     if(X == 0) {
>         return 1;
>     } else {
>         int temp = fact!(X - 1)();
>         return X * temp;
>     }
> }
> 
> const someVar = fact!(0)();
> ---

Like Moritz said. You need to use "static if" there rather than "if".

Moritz Warning escribió:
> On Sun, 24 May 2009 20:49:53 -0300, Ary Borenszweig wrote:
> 
>> When I compile this code I get "stack overflow" printed in the console.
>> Anyone know why?
>>
>> ---
>> int fact(int X)() {
>> 	if(X == 0) {
>> 		return 1;
>> 	} else {
>> 		int temp = fact!(X - 1)();
>> 		return X * temp;
>> 	}
>> }
>>
>> const someVar = fact!(0)();
>> ---
> 
> Because you generate fact!(-1)(), fact!(-2)() and so on at compile time.
> You recursive template doesn't terminate.

Thanks. Later in my head I instantiated the template and noticed the problem.

Ary Borenszweig:
> Thanks. Later in my head I instantiated the template and noticed the problem.

In time I have created similar problems in my code 2-3 times, missing a "static" before some "if".
Can't the compiler help spot such bugs? If the variables a dynamic if works on are constants (expecially if they are types) the compiler may give a warning...

Bye,
bearophile