Function prototype: Difference between revisions
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int anyargs(); /* An empty parameter list can be used to declare a function that accepts varargs */ |
int anyargs(); /* An empty parameter list can be used to declare a function that accepts varargs */ |
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int atleastoneargs(int, ...); /* One mandatory integer argument followed by varargs */</lang> |
int atleastoneargs(int, ...); /* One mandatory integer argument followed by varargs */</lang> |
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=={{header|C sharp}}== |
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'''Abstract methods'''<br/> |
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Interfaces and abstract classes can define abstract methods that must be implemented by subclasses. |
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<lang csharp>using System; |
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abstract class Printer |
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{ |
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public abstract void Print(); |
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} |
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class PrinterImpl : Printer |
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{ |
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public override void Print() { |
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Console.WriteLine("Hello world!"); |
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} |
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}</lang> |
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'''Delegates'''<br/> |
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A delegate is similar to a function pointer. They are multicast: multiple methods can be attached to them. |
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<lang csharp>using System; |
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public delegate int IntFunction(int a, int b); |
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public class Program |
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{ |
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public static int Add(int x, int y) { |
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return x + y; |
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} |
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public static int Multiply(int x, int y) { |
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return x * y; |
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} |
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public static void Main() { |
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IntFunction func = Add; |
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Console.WriteLine(func(2, 3)); //prints 5 |
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func = Multiply; |
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Console.WriteLine(func(2, 3)); //prints 6 |
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func += Add; |
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Console.WriteLine(func(2, 3)); //prints 5. Both functions are called, but only the last result is kept. |
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} |
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}</lang> |
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'''Partial methods'''<br/> |
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A partial type is a type that is defined in multiple files.<br/> |
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A partial method has its signature defined in one part of a partial type, and its implementation defined in another part of the type. If it is not implemented, the compiler removes the signature at compile time.<br/> |
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The following conditions apply to partial methods:<br/> |
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- Signatures in both parts of the partial type must match.<br/> |
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- The method must return void.<br/> |
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- No access modifiers are allowed. Partial methods are implicitly private. |
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<lang csharp>//file1.cs |
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public partial class Program |
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{ |
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partial void Print(); |
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} |
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//file2.cs |
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using System; |
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public partial class Program |
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{ |
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partial void Print() { |
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Console.WriteLine("Hello world!"); |
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} |
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static void Main() { |
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Program p = new Program(); |
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p.Print(); //If the implementation above is not written, the compiler will remove this line. |
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} |
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}</lang> |
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=={{header|C++}}== |
=={{header|C++}}== |
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