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A const parameter in pass-by-reference means that the referenced value is not modified – it is part of the contract – while a const parameter in pass-by-value (or the pointer itself, in pass-by-reference) does not add anything to the interface (as the value has been copied), but indicates that internally, the function does not modify the ...
int f (int z, int * k) {//function accepts an int (by value) and a pointer to int (also by value) as parameter z = 1; // idem Pascal, local value is modified but outer u will not be modified * k = 1; // variable referenced by k (eg, t) will be modified // up to here, z exists and equals 1} x = f (u, & t); // the value of u and the (value of ...
The specification for pass-by-reference or pass-by-value would be made in the function declaration and/or definition. Parameters appear in procedure definitions; arguments appear in procedure calls. In the function definition f(x) = x*x the variable x is a parameter; in the function call f(2) the value 2 is the argument of the function.
For a simple type like a number these conventions are relatively clear. Passing ByRef allows the procedure to modify the passed variable whereas passing ByVal does not. For an object, semantics can confuse programmers since an object is always treated as a reference. Passing an object ByVal copies the reference; not the state of the object. The ...
Unlike C++, C# does not permit methods and parameters to be marked as const. However one may also pass around read-only subclasses, and the .NET Framework provides some support for converting mutable collections to immutable ones which may be passed as read-only wrappers.
In the following tables, lower case letters such as a and b represent literal values, object/variable names, or l-values, as appropriate. R, S and T stand for a data type, and K for a class or enumeration type. Some operators have alternative spellings using digraphs and trigraphs or operator synonyms.
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In the C++ programming language, a reference is a simple reference datatype that is less powerful but safer than the pointer type inherited from C.The name C++ reference may cause confusion, as in computer science a reference is a general concept datatype, with pointers and C++ references being specific reference datatype implementations.