Template constraints in D

[Dee Girl]

Walter Bright Wrote:

> bearophile wrote:
> > They look nice (but I may use a bigger list of examples to understand
> > how they can be used). What can they do that can't be done with the
> > things already present?
> > 
> > bool isprime(int n) { ... } template Foo(int N) { static assert
> > (isprime(N), "error"); ... }
> > 
> > 
> > template Foo(int N) { static if (N & 1) { // A code } else { // B
> > code } Foo!(3)    // instantiates Foo with A code Foo!(64)   //
> > instantiates Foo with B code
> 
> Very good question. The answer is that the user can add overloads that 
> handle more cases without having to edit the original (which may be in a 
> module that is not editable for various reasons).

Good example is a hashtable. If the bucket size is prime then use a strategy. If is a power of two use another strategy. Otherwise use third strategy. Thanks, Dee Girl