Function overloading
Regan Heath
regan at netmail.co.nz
Tue Jul 31 02:05:22 PDT 2007
Vladimir wrote:
> Hi there,
>
> Why not to allow template function overloading? Like
>
> void test (T) (T)
> {
> }
>
> void test (int)
> {
> }
It is:
import std.stdio;
void test(T)(T p)
{
writefln("misc called");
}
void test(T : int)(T p)
{
writefln("int called");
}
void main()
{
int i;
long l;
float f;
test!(int)(i);
test!(long)(l);
test!(float)(f);
}
Output:
int called
misc called
misc called
However, without the !(int) etc it fails to compile with: "template
tplspec.test(T : int) specialization not allowed for deduced parameter T"
Given the documentation:
<copy>
Argument Deduction
The types of template parameters are deduced for a particular template
instantiation by comparing the template argument with the corresponding
template parameter.
For each template parameter, the following rules are applied in order
until a type is deduced for each parameter:
1. If there is no type specialization for the parameter, the type of
the parameter is set to the template argument.
2. If the type specialization is dependent on a type parameter, the
type of that parameter is set to be the corresponding part of the type
argument.
3. If after all the type arguments are examined there are any type
parameters left with no type assigned, they are assigned types
corresponding to the template argument in the same position in the
TemplateArgumentList.
4. If applying the above rules does not result in exactly one type
for each template parameter, then it is an error.
</copy>
It seems that for the first call "foo(i)" step #1 does nothing, step #2
sets the type to 'int', step #3 does nothing and step #4 finds that
there _is_ exactly 1 type per argument so why the error?
Is this a bug?
Regan
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