Hi,

Is there a way in D to specify function attributes for a template struct/class by type?

E.g. given  a template struct/class as follows:

---
struct S(T) {
    T[] values;
    void someFunc(int i) pure nothrow @safe {}
}
---

For some types the pure, nothrow, @safe attributes are valid and for others they're not.

I'd rather not duplicate each function body just to get attributes working.

Hmm, just had a thought, would this work??
---

struct S(T) {
    T[] values;
    private void someFuncImpl()(int i) {
         // the impl goes here with auto-deduced attributes
    }
    // Here's the public interface
    static if(is(T == SOME_TYPE)) {
        void someFunc(int i) pure nothrow @safe {this.someFuncImpl(i);}
    } else {
        void someFunc(int i) {this.someFuncImpl(i);}
    }
}
---

 ...  and is it "good" D?

If it works it's still annoying, but saves duplicating the impl.


thanks,
amber

On Thursday, 12 March 2015 at 03:12:15 UTC, amber wrote:
> ...
http://dlang.org/function.html#function-attribute-inference might be a good read if you haven't read it already.

On Thursday, 12 March 2015 at 04:04:28 UTC, weaselcat wrote:
> On Thursday, 12 March 2015 at 03:12:15 UTC, amber wrote:
>> ...
> http://dlang.org/function.html#function-attribute-inference might be a good read if you haven't read it already.

I did read it but didn't really understand it, so I've come to D.learn for more help.

I think it means I can just write the function like so:

struct S(T) {
    someFunc(int i) {// impl}
}

and if possible it will be pure, nothrow, @safe and @nogc.



thanks,
amber

On Thursday, 12 March 2015 at 04:51:42 UTC, amber wrote:
> On Thursday, 12 March 2015 at 04:04:28 UTC, weaselcat wrote:
>> On Thursday, 12 March 2015 at 03:12:15 UTC, amber wrote:
>>> ...
>> http://dlang.org/function.html#function-attribute-inference might be a good read if you haven't read it already.
>
> I did read it but didn't really understand it, so I've come to D.learn for more help.
>
> I think it means I can just write the function like so:
>
> struct S(T) {
>     someFunc(int i) {// impl}
> }
>
> and if possible it will be pure, nothrow, @safe and @nogc.
>
>
>
> thanks,
> amber

This works nicely after checking with __traits(getFunctionAttributes, S!T.someFunc)

Very cool :)

bye,
amber

On Thursday, 12 March 2015 at 05:01:50 UTC, amber wrote:
> On Thursday, 12 March 2015 at 04:51:42 UTC, amber wrote:
>> On Thursday, 12 March 2015 at 04:04:28 UTC, weaselcat wrote:
>>> On Thursday, 12 March 2015 at 03:12:15 UTC, amber wrote:
>>>> ...
>>> http://dlang.org/function.html#function-attribute-inference might be a good read if you haven't read it already.
>>
>> I did read it but didn't really understand it, so I've come to D.learn for more help.
>>
>> I think it means I can just write the function like so:
>>
>> struct S(T) {
>>    someFunc(int i) {// impl}
>> }
>>
>> and if possible it will be pure, nothrow, @safe and @nogc.
>>
>>
>>
>> thanks,
>> amber
>
> This works nicely after checking with __traits(getFunctionAttributes, S!T.someFunc)
>
> Very cool :)
>
> bye,
> amber

You can also use the __PRETTY_FUNCTION__ keyword to display information about a function.
http://dlang.org/traits.html#specialkeywords

On Thu, 12 Mar 2015 04:51:40 +0000, amber wrote:

> On Thursday, 12 March 2015 at 04:04:28 UTC, weaselcat wrote:
>> On Thursday, 12 March 2015 at 03:12:15 UTC, amber wrote:
>>> ...
>> http://dlang.org/function.html#function-attribute-inference might be a good read if you haven't read it already.
> 
> I did read it but didn't really understand it, so I've come to D.learn for more help.
> 
> I think it means I can just write the function like so:
> 
> struct S(T) {
>      someFunc(int i) {// impl}
> }
> 
> and if possible it will be pure, nothrow, @safe and @nogc.

yes. all templated functions (and `someFunc()` is templated due to `S` being templated) are subjects of attribute inference. due to this fact people sometimes writing even free functions as argument-less templates,

  void freeFunc() (...) { ... }

so compiler will infer attributes for `freeFunc()`. this has almost no cost, as compiler will merge all produced templates into one.