Parameter names in a std::function typedef

Question

I know I can typedef a std::function like so:

typedef std::function<void (const std::string&)> TextChangedHandler

Is it permitted to specify parameter names in the typedef, in order to make it more self-documenting? For example:

typedef std::function<void (const std::string& text)> TextChangedHandler

I can add parameter names and it compiles fine on Visual C++ 2010, but I wanted to make sure that it's allowed by the C++03/C++11 standards.

Answer 1

Yes.

This form of specifying a function type with no declarator naming the function is syntactically a type-id (8.1):

type-id:
    type-specifier-seq abstract-declarator[opt]

abstract-declarator:
    ptr-operator abstract-declarator[opt]
    direct-abstract-declarator

direct-abstract-declarator:
    direct-abstract-declarator[opt] ( parameter-declaration-clause ) cv-qualifier-seq exception-specification
    direct-abstract-declarator[opt] [ constant-expression ]
    ( abstract-declarator )

The parameter-declaration-clause syntax is the same as in ordinary function declarations, and it allows each argument to either have a name (declarator) or not (abstract-declarator) (8.3.5):

parameter-declaration-clause:
    parameter-declaration-list[opt] ...[opt]
    parameter-declaration-list[opt] , ...

parameter-declaration-list:
    parameter-declaration
    parameter-declaration-list , parameter-declaration

parameter-declaration:
    decl-specifier-seq declarator
    decl-specifier-seq declarator = assignment-expression
    decl-specifier-seq abstract-declarator[opt]
    decl-specifier-seq abstract-declarator[opt] = assignment-expression

Answer 2

Yes you can specify parameter names just as with regular function pointers. Keep in mind though these names are only valuable for documenting the function they have no 'real' effect.