function-declaration

问题 I see that in the answer of In Javascript, why write "var QueryStringToHash = function QueryStringToHash (query) { ... }"? which is doing something like var foo = function foo(param) { ... } in that particular case, why do that instead of just using function foo(param) { ... } ? What is the advantage or motivation of doing that? 回答1: In shortly, if you take the following code, the first example creates a function, named foo , the second example creates an anonymous function and assign it to

问题 6.7.6 Declarators says Each declarator declares one identifier , and asserts that when an operand of the same form as the declarator appears in an expression, it designates a function or object with the scope, storage duration, and type indicated by the declaration specifiers. And also states about syntax of parameter: parameter-declaration: declaration-specifiers declarator declaration-specifiers abstract-declarator(opt) For the given function prototype int f( int a[], int n); int a[]

问题 In such a situation namespace n { void f() { void another_function(); } } Should the function another_function be defined inside the namespace n or outside? VS 2012 (with the November CTP) says it should be outside, and GCC 4.7.2 on the Mac says it should be inside. If I do the wrong one, I get undefined symbol errors from the linkers. I generally trust GCC to be more compliant to the standard, but this is C++ and you can never be sure. 回答1: C++11 3.5 (as well as C++03) 7 When a block scope

问题 In such a situation namespace n { void f() { void another_function(); } } Should the function another_function be defined inside the namespace n or outside? VS 2012 (with the November CTP) says it should be outside, and GCC 4.7.2 on the Mac says it should be inside. If I do the wrong one, I get undefined symbol errors from the linkers. I generally trust GCC to be more compliant to the standard, but this is C++ and you can never be sure. 回答1: C++11 3.5 (as well as C++03) 7 When a block scope

问题 Local function declaration seems to be permitted in gcc, and I found a discussion on this: Is there any use for local function declarations? However, my question is: is it allowed by ISO C standard? If it is, how to explain the following phenomenon which makes it puzzling: int main(void) { int f(void); f(); } void g(void) { /* g has no idea about f. It seems that the decl is limited within its * scope */ f(); } int f(void) {} while int main(void) { int f(void); f(); } void f(void); /* error

问题 From § 8.3.5.11 of ISO/IEC 14882:2011(E): A typedef of function type may be used to declare a function but shall not be used to define a function The standard goes on to give this example: typedef void F(); F fv; // OK: equivalent to void fv(); F fv { } // ill-formed void fv() { } // OK: definition of fv What motivates this rule? It seems to limit the potential expressive usefulness of function typedefs. 回答1: Though this question is about C++, but since C++ inherits typedef and function pointer

问题 From § 8.3.5.11 of ISO/IEC 14882:2011(E): A typedef of function type may be used to declare a function but shall not be used to define a function The standard goes on to give this example: typedef void F(); F fv; // OK: equivalent to void fv(); F fv { } // ill-formed void fv() { } // OK: definition of fv What motivates this rule? It seems to limit the potential expressive usefulness of function typedefs. 回答1: Though this question is about C++, but since C++ inherits typedef and function pointer

问题 How to I define the equivalent of this function (taken from learnyouahaskell) inside GHCi? import Data.List numUniques :: (Eq a) => [a] -> Int numUniques = length . nub Without the type declaration, GHCi accepts the function definition, but it ends up with an unhelpful type: Prelude Data.List> import Data.List Prelude Data.List> let numUniques' = length . nub Prelude Data.List> :t numUniques' numUniques' :: [()] -> Int The resulting function only accepts a list of units as a parameter. Is

问题 How to I define the equivalent of this function (taken from learnyouahaskell) inside GHCi? import Data.List numUniques :: (Eq a) => [a] -> Int numUniques = length . nub Without the type declaration, GHCi accepts the function definition, but it ends up with an unhelpful type: Prelude Data.List> import Data.List Prelude Data.List> let numUniques' = length . nub Prelude Data.List> :t numUniques' numUniques' :: [()] -> Int The resulting function only accepts a list of units as a parameter. Is

问题 What's the difference between inline function and then main like so: inline double cube(double side) { return side * side * side; } int main( ) { cube(5); } vs just declaring a function regularly like: double cube(double side) { return side * side * side; } int main( ) { cube(5); } vs function prototype? double cube(double); int main( ) { cube(5); } double cube(double side) { return side * side * side; } 回答1: An inline function can be defined in multiple translation units (cpp file + includes