Re: Overloading doesn't work like described in "The D programming language"

[Steven Schveighoffer]

On Wed, 07 Dec 2011 16:35:04 -0500, Michael Kremser  
 wrote:



Hi!

On pages 145 and 146 (§ 5.5.1) of "The D programming language" there is  
an example with overloading a function with uint, long, and a  
parameterized type. I tried to reproduce that using a similar example:



module main;

import std.stdio;

void overloadme(uint number)
{
writeln("This is overloadme with uint.");
}

void overloadme(long number)
{
writeln("This is overloadme with long.");
}

void overloadme(T)(T number)
{
writeln("Generic overloadme called.");
}

int main(string[] argv)
{
overloadme(25);
overloadme("Bla");

writeln("\nFinished");
readln();
return 0;
}


However, if I try to compile that code, the compiler yields an error in  
line 15:


Error: template main.overloadme(T) conflicts with function  
main.overloadme at main.d(5)


In the book it says that "non-generic functions are generally preferred  
to generic functions, even when the non-generic function need an  
implicit conversion". But in my case that doesn't work.


Can anyone explain me what's going on here? Is the example in the book  
wrong or did I misinterpret something?


The compiler has not implemented overloads with templates yet.

Looks like there isn't a bug on it yet...

-Steve

Re: Overloading doesn't work like described in "The D programming language"

[Jonathan M Davis]

On Wednesday, December 07, 2011 22:35:04 Michael Kremser wrote:
> Hi!
> 
> On pages 145 and 146 (§ 5.5.1) of "The D programming language" there is
> an example with overloading a function with uint, long, and a
> parameterized type. I tried to reproduce that using a similar example:
> 
> 
> module main;
> 
> import std.stdio;
> 
> void overloadme(uint number)
> {
> writeln("This is overloadme with uint.");
> }
> 
> void overloadme(long number)
> {
> writeln("This is overloadme with long.");
> }
> 
> void overloadme(T)(T number)
> {
> writeln("Generic overloadme called.");
> }
> 
> int main(string[] argv)
> {
> overloadme(25);
> overloadme("Bla");
> 
> writeln("\nFinished");
> readln();
> return 0;
> }
> 
> 
> However, if I try to compile that code, the compiler yields an error in
> line 15:
> 
> Error: template main.overloadme(T) conflicts with function
> main.overloadme at main.d(5)
> 
> In the book it says that "non-generic functions are generally preferred
> to generic functions, even when the non-generic function need an
> implicit conversion". But in my case that doesn't work.
> 
> Can anyone explain me what's going on here? Is the example in the book
> wrong or did I misinterpret something?

Currently, you cannot overload templated functions with non-templated ones. It 
should be fixed at some point, but it hasn't been yet. There's a bug report on 
it: http://d.puremagic.com/issues/show_bug.cgi?id=2972

The workaround is to templatize the non-templated functions with an empty 
template parameter list. e.g.

void overloadme(uint number)

becomes

void overloadme()(uint number)

- Jonathan M Davis