template bug?

[Koroskin Denis]

On Fri, 29 Feb 2008 08:35:02 +0300, Denton Cockburn <diboss at hotmail.com>  
wrote:

> In DMD 2.011
>
> import std.stdio;
>
> template factorial(real n)
> {
> 	static if (n == 1)
> 		const factorial = 1;
> 	else const factorial = n * factorial!(n - 1);
> }
>
> void main()
> {
> 	writefln(factorial!(5));
> }
>
> produces: -3.10504e+231
>
> when the template is changed to accept an int instead of a real, it
> produces the right output: 120
>
> What's the cause of this?
>
> Note: in 1.027, the version accepting a real still produces the correct
> output of 120.

Seems like a bug to mee, too. This produces incorrect output as well:

template factorial(real n) {
     const real factorial = 1;
}

void main() {
     writefln(factorial!(5));
}

In C++, one cannot use real as a template parameter. The following code  
won't compile, although the code looks harmless :)

template<float t> class SomeClass {
     static const float someValue = t;
}

void main() {
    float value = SomeClass<5.0f>::someValue;  // 5.0f expected
}

However this one can easily instanciate as much templates, at it wishes  
because of rounding error on floating point arithmetics:

template<float t> float factorial() {
     if (t == 1) {	///< this condition might never be satisfied
         return 1;
     } else {
         return t*factorial(t-1);
     }
}

int main() {
    float t1 = factorial<5.0f>();
    float t2 = factorial<5.1f>();
}