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digitalmars.D - [hackathon] An article about metaprogramming

reply "Mafi" <mafi example.org> writes:
Hello there,

I took the occasion of the D hackathon to finally write a 
technical article. I am programming games as a hobby and find the 
D programming language perfectly suited for this task. So I 
thought I could write an article about how I use D's capabilities 
to program games efficiently.

So here it is: 
https://marfisc.wordpress.com/2015/04/29/using-d-templates-for-gamedev/

What do you think? Any remarks?

Mafi
Apr 29 2015
next sibling parent Andrei Alexandrescu <SeeWebsiteForEmail erdani.org> writes:
On 4/29/15 8:26 AM, Mafi wrote:

 Hello there,

 I took the occasion of the D hackathon to finally write a technical
 article. I am programming games as a hobby and find the D programming
 language perfectly suited for this task. So I thought I could write an
 article about how I use D's capabilities to program games efficiently.

 So here it is:
 https://marfisc.wordpress.com/2015/04/29/using-d-templates-for-gamedev/

 What do you think? Any remarks?

 Mafi


https://www.reddit.com/r/programming/comments/34ah1q/using_d_templates_for_game_development/

https://news.ycombinator.com/newest

https://twitter.com/D_Programming/status/593450243942940672

https://www.facebook.com/dlang.org/posts/1059784987368515


Andrei
Apr 29 2015
prev sibling next sibling parent reply "bearophile" <bearophileHUGS lycos.com> writes:
Mafi:


 https://marfisc.wordpress.com/2015/04/29/using-d-templates-for-gamedev/

 What do you think? Any remarks?



The SDL_Event is a union. Accessing it is inherently unsafe for 
type consistency and memory safety. The SDL library mitigates 
this problem by adding a tag (the member type) which encodes 
which union-member is to be used.<


In Rust you use the built-in tagged unions and call it a day...



switch(polledEvent.type) {
     mixin(caseOnEvent!("SDL_QUIT", "quit"));
     mixin(caseOnEvent!("SDL_ACTIVEEVEENT", "active"));
     mixin(caseOnEvent!("SDL_KEYDOWN", "eventKeyDown")); // (*)
     mixin(caseOnEvent!("SDL_KEYUP", "eventKeyUp")); // (*)
     mixin(caseOnEvent!("SDL_MOUSEMOTION", "motion"));
     mixin(caseOnEvent!("SDL_MOUSEBUTTONUP", 
"eventMouseButtonUp")); // (*)
     mixin(caseOnEvent!("SDL_MOUSEBUTTONDOWN", 
"eventMouseButtonDown")); // (*)
     mixin(caseOnEvent!("SDL_JOYAXISMOTION", "jaxis"));
     mixin(caseOnEvent!("SDL_JOYBALLMOTION", "jball"));
     mixin(caseOnEvent!("SDL_JOYHATMOTION", "jhat"));
     mixin(caseOnEvent!("SDL_JOYBUTTONDOWN", 
"eventJoyButtonDown")); // (*)
     mixin(caseOnEvent!("SDL_JOYBUTTONUP", "eventJoyButtonUp")); 
// (*)
     mixin(caseOnEvent!("SDL_USEREVENT", "user"));
     mixin(caseOnEvent!("SDL_SYSWMEVENT", "syswm"));
default: //has to be there even if empty
     static if(is(typeof(that.onOther(Event.init)))) {
         that.onOther(polledEvent); break;
     }
}

The default should be aligned just like the other cases. Often is 
a good idea to use "final switch" with enumerations.
Probably there are ways to make that code more dry, using a 
TypeTuple of pairs like ("SDL_QUIT", "quit").

Bye,
bearophile
Apr 29 2015
parent reply "Mafi" <mafi example.org> writes:
On Wednesday, 29 April 2015 at 16:55:58 UTC, bearophile wrote:

 Mafi:


 https://marfisc.wordpress.com/2015/04/29/using-d-templates-for-gamedev/

 What do you think? Any remarks?



The SDL_Event is a union. Accessing it is inherently unsafe for 
type consistency and memory safety. The SDL library mitigates 
this problem by adding a tag (the member type) which encodes 
which union-member is to be used.<


 In Rust you use the built-in tagged unions and call it a day...


Well, it is an already existing C library I am only adapting. And 
additionally the shonwn template encapsulates the whole outer 
loop as well.


[...]

 The default should be aligned just like the other cases. Often 
 is a good idea to use "final switch" with enumerations.
 Probably there are ways to make that code more dry, using a 
 TypeTuple of pairs like ("SDL_QUIT", "quit").

 Bye,
 bearophile


I cannot use a final switch there because it is not enumerated 
type. The values are just constants. Moreover I want to skip 
unneeded labels and instead unify them into the default branch. 
This is impossible with a final switch.
Apr 29 2015
parent "Idan Arye" <GenericNPC gmail.com> writes:
On Wednesday, 29 April 2015 at 18:13:10 UTC, Mafi wrote:

 On Wednesday, 29 April 2015 at 16:55:58 UTC, bearophile wrote:

 Mafi:


 https://marfisc.wordpress.com/2015/04/29/using-d-templates-for-gamedev/

 What do you think? Any remarks?



The SDL_Event is a union. Accessing it is inherently unsafe 
for type consistency and memory safety. The SDL library 
mitigates this problem by adding a tag (the member type) which 
encodes which union-member is to be used.<


 In Rust you use the built-in tagged unions and call it a day...


 Well, it is an already existing C library I am only adapting. 
 And additionally the shonwn template encapsulates the whole 
 outer loop as well.


[...]

 The default should be aligned just like the other cases. Often 
 is a good idea to use "final switch" with enumerations.
 Probably there are ways to make that code more dry, using a 
 TypeTuple of pairs like ("SDL_QUIT", "quit").

 Bye,
 bearophile


 I cannot use a final switch there because it is not enumerated 
 type. The values are just constants. Moreover I want to skip 
 unneeded labels and instead unify them into the default branch. 
 This is impossible with a final switch.


If you invest some effort in redefining the event types as D 
structs and the event codes as a D enum, you can get rid of that 
routing-list construct altogether: 
http://dpaste.dzfl.pl/1e992d248355
Apr 30 2015
prev sibling parent "weaselcat" <weaselcat gmail.com> writes:
On Wednesday, 29 April 2015 at 15:26:58 UTC, Mafi wrote:

 Hello there,

 I took the occasion of the D hackathon to finally write a 
 technical article. I am programming games as a hobby and find 
 the D programming language perfectly suited for this task. So I 
 thought I could write an article about how I use D's 
 capabilities to program games efficiently.

 So here it is: 
 https://marfisc.wordpress.com/2015/04/29/using-d-templates-for-gamedev/

 What do you think? Any remarks?

 Mafi


I think the article highlights the issue with the current 
std.variant implementation, lack of pattern 
matching/destructuring in D, and need for better tuple syntax.
Nice article
Apr 29 2015