On 03/02/2011 08:56 PM, Peter Lundgren wrote:
Where can I go to learn about parameterized structs? I can't seem to find any
literature on the subject. In particular, what are you allowed to use as a
parameter? I would like to define a struct like so:
struct MyStruct(T, T[] a) {
...
}
but I receive the following error:
Error: arithmetic/string type expected for value-parameter, not T[]
Are arrays not allowed?
Are you trying to parametrize by the type of the container or just
trying to use an array of a specified type? (As opposed to say, a linked
list of the specified type?)
If the former, it's simple. And the simplest thing is to just use an
array in the implementation:
struct S(T)
{
T[] a;
void foo(T element)
{
/* Just use like an array */
a ~= element;
a[0] = element;
}
}
void main()
{
auto s = S!double();
s.foo(1.5);
}
If you want to use a different container of the specified T, then a
second template parameter can be used. This one uses an array as the
default one:
class SomeContainer
{}
struct S(T, Cont = T[])
{
Cont a;
void foo(T element)
{
/* This time the use must match the allowed container types */
}
}
void main()
{
auto s = S!(double, SomeContainer)();
s.foo(1.5);
}
I would recommend pulling information out ;) of this page:
http://digitalmars.com/d/2.0/template.html
"Template Alias Parameters" is very different after C++ and can be very
powerful:
http://digitalmars.com/d/2.0/template.html#TemplateAliasParameter
Ali
