hey.

is this valid code?

void func1(int i, double j = 1.0) {
}

void main() {
    auto fn = &func1;
    func1(1); //dmd: ok
    fn(1); // dmd: not ok
}

On 08/22/2012 11:51 AM, Ellery Newcomer wrote:
> hey.
>
> is this valid code?
>
> void func1(int i, double j = 1.0) {
> }
>
> void main() {
> auto fn = &func1;
> func1(1); //dmd: ok
> fn(1); // dmd: not ok
> }

The type of the function pointer does not include the values of the default parameters.

The type of fn is "a function taking int and a double, returning nothing". So the compiler must require that information at the call site.

The alternative could work too: The compiler could keep a table from function pointers to default parameters. But that would be slow.

I am not surprised by dmd's behavior.

Ali

On 08/22/2012 12:03 PM, Ali Çehreli wrote:
> On 08/22/2012 11:51 AM, Ellery Newcomer wrote:
>  > hey.
>  >
>  > is this valid code?
>  >
>  > void func1(int i, double j = 1.0) {
>  > }
>  >
>  > void main() {
>  > auto fn = &func1;
>  > func1(1); //dmd: ok
>  > fn(1); // dmd: not ok
>  > }
>
> The type of the function pointer does not include the values of the
> default parameters.

typeof lies.

pragma(msg, typeof(fn));

> void function(int i, double j = 1)

On Wednesday, August 22, 2012 11:51:45 Ellery Newcomer wrote:
> hey.
> 
> is this valid code?
> 
> void func1(int i, double j = 1.0) {
> }
> 
> void main() {
> auto fn = &func1;
> func1(1); //dmd: ok
> fn(1); // dmd: not ok
> }

Default arguments are not part of the type. This behavior is very much on purpose.

http://d.puremagic.com/issues/show_bug.cgi?id=3866 http://d.puremagic.com/issues/show_bug.cgi?id=8402 http://d.puremagic.com/issues/show_bug.cgi?id=8515

- Jonathan M Davis

On 08/22/2012 12:15 PM, Ellery Newcomer wrote:
> On 08/22/2012 12:03 PM, Ali Çehreli wrote:
>> On 08/22/2012 11:51 AM, Ellery Newcomer wrote:
>> > hey.
>> >
>> > is this valid code?
>> >
>> > void func1(int i, double j = 1.0) {
>> > }
>> >
>> > void main() {
>> > auto fn = &func1;
>> > func1(1); //dmd: ok
>> > fn(1); // dmd: not ok
>> > }
>>
>> The type of the function pointer does not include the values of the
>> default parameters.
>
> typeof lies.
>
> pragma(msg, typeof(fn));
>
>  > void function(int i, double j = 1)
>

Opened:

  http://d.puremagic.com/issues/show_bug.cgi?id=8579

Ali