Jump to content
  • Advertisement
Sign in to follow this  
  • entries
  • comments
  • views

Two things I wish C++ had.

Sign in to follow this  


I thought I'd share some thoughts on two features I wished C++ had, tell me what you think.

Identifier Template Parameters

I'd really like to be able to take an identifier token as a template parameter, similar to a macro but it could only accept a single identifier.

You could use it somewhat like this.template void AddOne (T &value){ ++value.variablename;}
ortemplate class NamedPair{public: T1 first; T2 second; ...pair like functions...};NamedPair pair;pair.A = 10;pair.B = 20;
You may be wondering why I would want such a feature. While there are more uses the one that prompted me to wish for this was a sort of "Compile Time Reflection" set of helpers. Similar to those in type_traits, but to check if a type has certain functions or variables.

You wouldn't need a macro to create SFINAE member checking classes anymore.template class has_member{ ... };class A{public: int foo;};class B{};has_member::value; //truehas_member::value; //false
Which means you could use std::enable_if to turn on and off functions based of the contents of a template parameter. Which would be really nifty.

You would probably need the equivalent of typedef for identifiers (alias?) if you were to use this in a more complex template situation something like...identdef foo bar;class A{public: int foo;};A.bar = 10;
Which could introduce a whole host of issues... maybe I haven't thought it all the way through.

Perfect Forwarding Without Templates

C++11 added R-Value references and move semantics which ease a lot of the pain from C++03. However to take advantage of this you need to handle forwarding R-Value and L-Value references properly. Which either means using a template or dealing with the permutation explosion of arguments.void A (const int &value){ ... }void A (int &&value){ ... }//ortemplate void A (T &&value){ ... }
Writing out the cases is ok if you have just one argument, but if you have more than one its time to use a template. But with a template you lose the ability to assert which type you would like to accept.template void B (T1 &&one, T2 &&two){ ... }
If I wanted to make sure B only excepted type "Foo" I could only use static asserts to inform the programmer. Instead I'd love to be able to write something likevoid B (Foo &@one, Foo &@two){ ... }
And have the compiler generate the permutations, just as the compiler does for template type && arguments. (Except enforcing type Foo). I chose an @ sign at random, its kind of ugly substitute what you wish.
Sign in to follow this  


Recommended Comments

Uhm, I'm not quite sure about the identifier thing, but I try to stay away from templates as much as I can so I guess I cannot appreciate those things in full.

Share this comment

Link to comment

Templates are exceptionally useful, as long as they aren't overly-used. There is quite a bit of fighting against non-simple templates to make them work, but once a templated function or class works, it works very well.

Share this comment

Link to comment

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
  • Advertisement

Important Information

By using GameDev.net, you agree to our community Guidelines, Terms of Use, and Privacy Policy.

GameDev.net is your game development community. Create an account for your GameDev Portfolio and participate in the largest developer community in the games industry.

Sign me up!