method-signature | 易学教程

What does this signature mean (&) in PHP?

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问题 Consider: public function & get($name, $default = null) Why & ? 回答1: In PHP's syntax, this means that the function returns a reference instead of a value. For example: <?php $foo = 'foo'; function & get_foo_ref () { global $foo; return $foo; } // Get the reference to variable $foo stored into $bar $bar = & get_foo_ref(); $bar = 'bar'; echo $foo; // Outputs 'bar', since $bar references to $foo. ?> In the above example, removing the & from the function declaration would make the $foo variable

Why varargs should be the last in method signature?

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If I try to write a method like below public void someStuff(Object ... args, String a ) I get this error The variable argument type Object of the method someStuff must be the last parameter. I don't fully understand the requirement of variable argument type to be the last. Any inputs will be helpful. It follows the C convention. The C convention in turn is based on CPU architectures which pass arguments on the stack. The first non-vararg arguments end up at a fixed offset in the stackframe. If you could put the vararg arguments first, the stack offset of the following arguments would depend on

Static member functions error; How to properly write the signature?

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问题 I am getting an error when trying to compile my code in g++ using the current signature: cannot declare member function static void Foo::Bar(std::ostream&, const Foo::Node*) to have static linkage My question is twofold: Why does it not Compile this way? What is the correct signature, and why? Signatures have always been the death of me when using C++ Edit: Here is the class header file, as well: class Foo { public: Foo(); ~Foo(); bool insert(const Foo2 &v); Foo * find(const Foo2 &v); const

Why can't two methods be declared with the same signature even though their return types are different? [duplicate]

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Duplicate : Function overloading by return type? Maybe this is a very silly question but I don't understand why I can't declare two methods that have the same signature when they have different return types. public class MyClass { private double d = 0; public double MyMethod() { return d; } public string MyMethod() { return d.ToString(); } } I get a compile error that states that the class already defines a member with the same parameter types. (Obviously the way I'm using this in my code isn't as simple as my example code...but I think it gets the idea across.) Am I missing something

Is it possible to write a Rust macro that will expand into a function/method signature?

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问题 I would love to be able to something like the following: macro_rules! impl_a_method( ($obj:ident, $body:block) => ( fn a_method(foo: Foo, bar: Bar, baz: Baz) -> $obj $body ) ) // Implementation would look like: impl_a_method!(MyType, { MyType { foo: foo.blah(), bar: bar.bloo(), baz: baz.floozy(), } }) My real-world example features methods with much larger signatures which I have to implement in unique ways for 30+ different types. I have tried something similar to the above macro, however I

How can an interface include a method that references the concrete implementation type of the interface in its signature or return type?

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问题 Suppose I am designing something like the following interface: public interface MyInterface{ public MyInterface method1(); public void method2(MyInterface mi); } However, there is the caveat that the return type for method1 and the parameter for method2 match the concrete implementation and not just MyInterface . That is, if I have MyInterfaceImpl that implements MyInterface , it needs to have the following: public class MyInterfaceImpl implements MyInterface{ @Override public MyInterfaceImpl

Why varargs should be the last in method signature?

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问题 If I try to write a method like below public void someStuff(Object ... args, String a ) I get this error The variable argument type Object of the method someStuff must be the last parameter. I don't fully understand the requirement of variable argument type to be the last. Any inputs will be helpful. 回答1: It follows the C convention. The C convention in turn is based on CPU architectures which pass arguments on the stack. The first non-vararg arguments end up at a fixed offset in the

Why can't two methods be declared with the same signature even though their return types are different? [duplicate]

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问题 This question already has answers here : Closed 10 years ago . Duplicate : Function overloading by return type? Maybe this is a very silly question but I don't understand why I can't declare two methods that have the same signature when they have different return types. public class MyClass { private double d = 0; public double MyMethod() { return d; } public string MyMethod() { return d.ToString(); } } I get a compile error that states that the class already defines a member with the same

How to return an array from a function?

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问题 How can I return an array from a method, and how must I declare it? int[] test(void); // ?? 回答1: int* test(); but it would be "more C++" to use vectors: std::vector< int > test(); EDIT I'll clarify some point. Since you mentioned C++, I'll go with new[] and delete[] operators, but it's the same with malloc/free. In the first case, you'll write something like: int* test() { return new int[size_needed]; } but it's not a nice idea because your function's client doesn't really know the size of

How to return an array from a function?

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How can I return an array from a method, and how must I declare it? int[] test(void); // ?? Simone int* test(); but it would be "more C++" to use vectors: std::vector< int > test(); EDIT I'll clarify some point. Since you mentioned C++, I'll go with new[] and delete[] operators, but it's the same with malloc/free. In the first case, you'll write something like: int* test() { return new int[size_needed]; } but it's not a nice idea because your function's client doesn't really know the size of the array you are returning, although the client can safely deallocate it with a call to delete[] . int