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Saying that C++ is internally consistent at all is a huge exaggeration. Actually I'd be very careful with stating it is more consistent than PHP. Both have many

Saying that C++ is internally consistent at all is a huge exaggeration. Actually I'd be very careful with stating it is more consistent than PHP. Both have many sharp-edges and in both there are plenty of features that feel "tacked on" and are non-orthogonal to each other. E.g. why I can't make a generic (template) function virtual or why I cannot overload some overloadable operators to have exactly same semantics as the builtin ones.

pjmlp 13y ago
In C++'s case "The Design and evolution of C++" is a good read to understand how the language turnout that way and why certain compromises were done.
- pkolaczk 13y ago
  Sure, all the inconsistencies have a nice explanation, I never questioned that. PHPs === operator has a nice explanation, too.
nly 13y ago
You can't make a member function template virtual because it's just a template, the function doesn't exist until it's statically instantiated. Instantiation can happen across units of compilation, making it impossible for the compiler to generate a vtable with all the instantiations within it. It's not a "tacked on" feature/limitation at all, and I don't see how any statically typed language that allowed function overloading could really work around that issue. I'm not sure what you mean about the operator overloading thing.
- pkolaczk 13y ago
  This was a rhetoric question. I perfectly know why I can't do that in C++. C++ does not allow this because of particular generics implementation (done by static compile-time macro expansion), not because those two features are inherently contradictory. In fact, they are completely orthogonal and Java/Scala/C# have no problems with that, despite being statically typed.
pandaman 13y ago
As nly pointed out - the virtual template function just does not make sense if you understand what it is. As for the operators I'd guess you mean && and ||? You cannot make them shortcut because the user defined operators are just functions and functions in C++ do always evaluate their arguments.
- pkolaczk 13y ago
  Virtual generic functions do make sense and many languages allow them. The problem is C++ implements them by compile-time macro expansion (called templates), which renders them impossible. Template types are also not really first-class members of the type system. The compiler can't really reason about them, it only type-checks them after expansion, when all the genericity disappears. This is completely different than the fail-fast approach in Haskell or even Java, where the code is type-checked at the generic level. Don't get me wrong - templates is an awesome, extremely powerful feature of C++, but it doesn't play well with the rest of the language, and really feels tacked-on.
  - pandaman 13y ago
    Sure, generic functions are awesome when you don't care about performance. This is why C++ does not have them. If you knew nothing about C++ and somebody told you "here, we have a language with zero run-time overhead, can you guess if we managed to implement generic functions?" what would you say? Function templates are not generic functions. Same as template classes are not types. They play really well with the rest of C++ but I agree, not so well with the rest of Java or Haskell :) This is the major problem people nowadays have with C++ - they learn some "practical" high-level language in school (usually riddled with random stuff, judging by how much people here are pissed with my mentioning of PHP) and try to think about C++ in concepts of such a language. Then blame C++ for not being their favorite language. Don't get me wrong. I am quite happy with this making my skills very rare and expensive, giving me both job security and decent compensation. I also want to thank all the people spreading the "C++ is complex hodgepodge of completely random things so it's impossible to learn" idea :)
    - 13y ago

pjmlp 13y ago

In C++'s case "The Design and evolution of C++" is a good read to understand how the language turnout that way and why certain compromises were done.

pkolaczk 13y ago
Sure, all the inconsistencies have a nice explanation, I never questioned that. PHPs === operator has a nice explanation, too.

nly 13y ago

You can't make a member function template virtual because it's just a template, the function doesn't exist until it's statically instantiated. Instantiation can happen across units of compilation, making it impossible for the compiler to generate a vtable with all the instantiations within it. It's not a "tacked on" feature/limitation at all, and I don't see how any statically typed language that allowed function overloading could really work around that issue. I'm not sure what you mean about the operator overloading thing.

pkolaczk 13y ago
This was a rhetoric question. I perfectly know why I can't do that in C++. C++ does not allow this because of particular generics implementation (done by static compile-time macro expansion), not because those two features are inherently contradictory. In fact, they are completely orthogonal and Java/Scala/C# have no problems with that, despite being statically typed.

pandaman 13y ago

As nly pointed out - the virtual template function just does not make sense if you understand what it is. As for the operators I'd guess you mean && and ||? You cannot make them shortcut because the user defined operators are just functions and functions in C++ do always evaluate their arguments.

pkolaczk 13y ago
Virtual generic functions do make sense and many languages allow them. The problem is C++ implements them by compile-time macro expansion (called templates), which renders them impossible. Template types are also not really first-class members of the type system. The compiler can't really reason about them, it only type-checks them after expansion, when all the genericity disappears. This is completely different than the fail-fast approach in Haskell or even Java, where the code is type-checked at the generic level. Don't get me wrong - templates is an awesome, extremely powerful feature of C++, but it doesn't play well with the rest of the language, and really feels tacked-on.
- pandaman 13y ago
  Sure, generic functions are awesome when you don't care about performance. This is why C++ does not have them. If you knew nothing about C++ and somebody told you "here, we have a language with zero run-time overhead, can you guess if we managed to implement generic functions?" what would you say? Function templates are not generic functions. Same as template classes are not types. They play really well with the rest of C++ but I agree, not so well with the rest of Java or Haskell :) This is the major problem people nowadays have with C++ - they learn some "practical" high-level language in school (usually riddled with random stuff, judging by how much people here are pissed with my mentioning of PHP) and try to think about C++ in concepts of such a language. Then blame C++ for not being their favorite language. Don't get me wrong. I am quite happy with this making my skills very rare and expensive, giving me both job security and decent compensation. I also want to thank all the people spreading the "C++ is complex hodgepodge of completely random things so it's impossible to learn" idea :)
  - 13y ago