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digitalmars.D.learn - auto function attributes based on type

reply "amber" <amber.swan gmail.com> writes:
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
Mar 11 2015
parent reply "weaselcat" <weaselcat gmail.com> writes:
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.
Mar 11 2015
parent reply "amber" <amber.swan gmail.com> writes:
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
Mar 11 2015
next sibling parent reply "amber" <amber.swan gmail.com> writes:
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
Mar 11 2015
parent "weaselcat" <weaselcat gmail.com> writes:
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
Mar 11 2015
prev sibling parent ketmar <ketmar ketmar.no-ip.org> writes:
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.


=20
 I did read it but didn't really understand it, so I've come to D.learn
 for more help.
=20
 I think it means I can just write the function like so:
=20
 struct S(T) {
      someFunc(int i) {// impl}
 }
=20
 and if possible it will be pure, nothrow,  safe and  nogc.


yes. all templated functions (and `someFunc()` is templated due to `S`=20
being templated) are subjects of attribute inference. due to this fact=20
people sometimes writing even free functions as argument-less templates,

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

so compiler will infer attributes for `freeFunc()`. this has almost no=20
cost, as compiler will merge all produced templates into one.=
Mar 12 2015