www.digitalmars.com         C & C++   DMDScript  

digitalmars.D.learn - Template type parameters with their own type parameters

reply Peter Lundgren <lundgrpb rose-hulman.edu> writes:
I have a function that I think should look something like this:

MyStruct!T myFunc(T)(MyStruct!T x, ...) {
	...
	return MyStruct!T(...);
}

and the closest I can get to is:

T myFunc(T)(T x, ...) {
	...
	return T(...);
}

which works, but doesn't make clear the intended use and gets in the way of
overloading. How can I express the intent of the first version.
Mar 04 2011
parent reply spir <denis.spir gmail.com> writes:
On 03/05/2011 04:02 AM, Peter Lundgren wrote:
 I have a function that I think should look something like this:

 MyStruct!T myFunc(T)(MyStruct!T x, ...) {
 	...
 	return MyStruct!T(...);
 }

 and the closest I can get to is:

 T myFunc(T)(T x, ...) {
 	...
 	return T(...);
 }

 which works, but doesn't make clear the intended use and gets in the way of
 overloading. How can I express the intent of the first version.

Maybe I do not exactly understand your problem; anyway, the following runs fine by me: struct S (T) { T v; } S!T inc (T) (S!T s) { return S!T(s.v + 1); } unittest { auto s1 = S!int(1); auto s2 = inc(s1); assert ( s2.v == 2 ); } Could you provide (1) context (2) example (3) errors? Denis -- _________________ vita es estrany spir.wikidot.com
Mar 05 2011
parent Peter Lundgren <lundgrpb rose-hulman.edu> writes:
== Quote from spir (denis.spir gmail.com)'s article
 On 03/05/2011 04:02 AM, Peter Lundgren wrote:
 I have a function that I think should look something like this:

 MyStruct!T myFunc(T)(MyStruct!T x, ...) {
 	...
 	return MyStruct!T(...);
 }

 and the closest I can get to is:

 T myFunc(T)(T x, ...) {
 	...
 	return T(...);
 }

 which works, but doesn't make clear the intended use and gets in the way of
 overloading. How can I express the intent of the first version.

by me: struct S (T) { T v; } S!T inc (T) (S!T s) { return S!T(s.v + 1); } unittest { auto s1 = S!int(1); auto s2 = inc(s1); assert ( s2.v == 2 ); } Could you provide (1) context (2) example (3) errors? Denis

Thanks for the help. I'd convinced myself that it didn't work and missed the actual problem. I was mixing template type and template value parameters. What I really wanted was this: MyStruct!v myFunc(string v)(MyStruct!v x, ...) { ... return MyStruct!v(...); }
Mar 05 2011