any suggestion for importing external generic method

[abakoboParticipant]

I’d like to finish the box2d modules and for that I only need to import some generic methods (from non generic struct).

The only thing missing then would be operators. I’ve seen that operators are not possible for now but I saw that it was almost ok in the output cpp file (just to say it). And after all, operators are an mx2 feature too.. So it would be great if we could import them (in my test the +cpp just had some postfix member operator and brackets to be removed and it compiled ok).

…But this topic is about external generic methods!

This is a method (Query) that I’d like to be able to call from mx2:

Monkey

[crayon-5cba1666985d6772321486 inline="true" ]class b2BroadPhase { public: template <typename T> void Query(T* callback, const b2AABB& aabb) const; . .

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[crayon-5cba1666985d6772321486 inline="true" ]class b2BroadPhase { public: template <typename T> void Query(T* callback, const b2AABB& aabb) const; . .

[/crayon]

I made simplified test to see how it could be imported. The global function with generics could be imported without problem and the passing by ref if OK! but the method was not…

test.monkey2

Monkey

[crayon-5cba1666985dd057981161 inline="true" ]Namespace myapp #Import "<std>" #Import "v2.h" Using std.. Extern struct sVect2 Field x:Float Field y:Float Method New() Method New(a:float,b:float) Method aroule:float (a:Float ptr) Method MSwap<T>(a:T,b:T) End Function FSwap<T>(a:T,b:T) Public Function Main() Local va:sVect2 va=New sVect2(1.0,2.0) Local vb:sVect2 vb=New sVect2(20.0,20.0) Local arr:=New Float[] (10.0,7.0) Print va.aroule(arr.Data) Print va.x+" "+vb.x FSwap (va,vb) 'this works with variables passed by reference Print va.x+" "+vb.x 'swap has succeded !! 'va.MSwap(va,vb) 'This one doesn't work (has 3 params instead of 2 and g++ says " 'MSwap' was not declared in this scope ") Print va.x+" "+vb.x ' :( End

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[crayon-5cba1666985dd057981161 inline="true" ]Namespace myapp #Import "<std>" #Import "v2.h" Using std..   Extern   struct sVect2 Field x:Float Field y:Float Method New() Method New(a:float,b:float) Method aroule:float (a:Float ptr) Method MSwap<T>(a:T,b:T) End   Function FSwap<T>(a:T,b:T)   Public   Function Main()   Local va:sVect2 va=New sVect2(1.0,2.0) Local vb:sVect2 vb=New sVect2(20.0,20.0) Local arr:=New Float[] (10.0,7.0) Print va.aroule(arr.Data) Print va.x+" "+vb.x FSwap (va,vb) 'this works with variables passed by reference Print va.x+" "+vb.x 'swap has succeded !! 'va.MSwap(va,vb) 'This one doesn't work (has 3 params instead of 2 and g++ says " 'MSwap' was not declared in this scope ") Print va.x+" "+vb.x ' :( End

[/crayon]

v2.h

Monkey

[crayon-5cba1666985e3503829564 inline="true" ]#ifndef V2_H #define V2_H struct sVect2 { float x, y; // sVect2() = default; // sVect2(float a, float b) { x = a; y = b; } // float aroule(float a[2]) { return a[0]+a[1]; } template<typename T> void MSwap(T& a, T& b) { T tmp = a; a = b; b = tmp; } }; // template<typename T> void FSwap(T& a, T& b) { T tmp = a; a = b; b = tmp; } #endif

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[crayon-5cba1666985e3503829564 inline="true" ]#ifndef V2_H #define V2_H   struct sVect2 { float x, y;     // sVect2() = default;     // sVect2(float a, float b) { x = a; y = b; }     // float aroule(float a[2]) { return a[0]+a[1]; } template<typename T> void MSwap(T& a, T& b) { T tmp = a; a = b; b = tmp; } }; // template<typename T> void FSwap(T& a, T& b) { T tmp = a; a = b; b = tmp; } #endif

[/crayon]

if I uncomment the line with MSwap I get this error:

Monkey

[crayon-5cba1666985e9362968457 inline="true" ] error: 'MSwap' was not declared in this scope MSwap(f0.l_va,f0.l_va,f0.l_vb);

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[crayon-5cba1666985e9362968457 inline="true" ] error: 'MSwap' was not declared in this scope    MSwap(f0.l_va,f0.l_va,f0.l_vb);

[/crayon]

any suggestion on how to deal with that T* method?

It’s fun to see that it has 3 parameters instead of 2 and that the additional parameter is actualy the instance that has the scope. So everything seem to be there but not well placed?!

[abakoboParticipant]

I just saw in the docs commit of yesterday that extern generic functions can not be imported. Global extern generic functions I tested did work though..

[Mark SiblyKeymaster]

I am VERY uncomfortable with attempting to support this (and ‘native’ operator overloading) for the simple reason I can’t guarantee it’ll work reliably all of the time without giving ‘weird’ results. In fact, I know it wont.

The main reason for this is that monkey2 doesn’t actually use native c++ generics or operator overloading when translating monkey2 code so they actually don’t work identically to c++’s. There are things you can do with monkey2 operators/generics that you CAN’T do in c++ because of this – and of course vice versa.

So sorry, but the current official line is ‘no native generics/operators’ (even if it’s not fully enforced yet) as I don’t want to have to support c++ generics/operators on top of having to support monkey2 generics/operators, if you see what I mean.

As for box2d, I believe there are existing wrappers around that don’t use generics (objc? bmx? monkeyx?) so it should at least be possible (if not as easy).

[abakoboParticipant]

Ok thanks for the info. Just wanted it to be as identical as possible to original box2D. Will wrap it around then. Don’t know what to do with generics global function though, because they actualy work, so I think I’ll keep them like that until(if) a problem occurs..

[Mark SiblyKeymaster]

Don’t know what to do with generics global function though

What do other wrappers do? I would recommend NOT leaving them as is though as I may prohibit extern generics altogether soon to prevent any confusion.

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