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I am not convinced that C++ examples are valid as a generalization of the failures of generics for other languages. C++ libraries are often overly generalized

by alok-g 13y ago

I am not convinced that C++ examples are valid as a generalization of the failures of generics for other languages. C++ libraries are often overly generalized with means to "configure" the generics by passing additional type arguments. I do not think it has to be like that.

davidcuddeback 13y ago
C++ templates are also latently typed. The bad error messages arise from the fact that C++ templates behave more like a duck-typed language than a strongly-typed language. Look at the error messages that arise from C++ template errors and a lot of them are about missing functions, just like you get at runtime when you have a type error is a dynamically-typed language. I think C++ concepts will improve this when they're standardized, because they will allow C++ compilers to type-check template arguments. (See bounded polymorphism.)
AnthonyMouse 13y ago
Some of it is also the fault of the compilers for being too explicit in their default error messages. You get that horrible output because string is really a typedef to "basic_string<char>" and basic_string takes two more template arguments with defaults. But why is the compiler resolving the typedef in the error message by default? At least let it be "std::map<std::string, std::string, std::less<std::string>, std::allocator<std::pair<std::string const, std::string> > >" instead of that inscrutable noise. And if you really need to provide the information that "std::string" is "std::basic_string<char, std::char_traits<char>, std::allocator<char> >" then put it on a separate line in the output, once, instead of repeating it internally within every recursive template instantiation.
- nikbackm 13y ago
  Maybe the typedef:s have been resolved and discarded at the point in compilation where the error is reported? So using it in the error message would require extra work.
  - rapala 13y ago
    So why do we pass that work from the compiler,the tool, to the programmer? Except that I think I know the reason, as I have looked upon the specification and it was not sane.

by alok-g 13y ago

davidcuddeback 13y ago

C++ templates are also latently typed. The bad error messages arise from the fact that C++ templates behave more like a duck-typed language than a strongly-typed language. Look at the error messages that arise from C++ template errors and a lot of them are about missing functions, just like you get at runtime when you have a type error is a dynamically-typed language. I think C++ concepts will improve this when they're standardized, because they will allow C++ compilers to type-check template arguments. (See bounded polymorphism.)

AnthonyMouse 13y ago

Some of it is also the fault of the compilers for being too explicit in their default error messages. You get that horrible output because string is really a typedef to "basic_string<char>" and basic_string takes two more template arguments with defaults. But why is the compiler resolving the typedef in the error message by default? At least let it be "std::map<std::string, std::string, std::less<std::string>, std::allocator<std::pair<std::string const, std::string> > >" instead of that inscrutable noise. And if you really need to provide the information that "std::string" is "std::basic_string<char, std::char_traits<char>, std::allocator<char> >" then put it on a separate line in the output, once, instead of repeating it internally within every recursive template instantiation.

nikbackm 13y ago
Maybe the typedef:s have been resolved and discarded at the point in compilation where the error is reported? So using it in the error message would require extra work.
- rapala 13y ago
  So why do we pass that work from the compiler,the tool, to the programmer? Except that I think I know the reason, as I have looked upon the specification and it was not sane.