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objective-clvaluervalue

What is LValues and RValues in objective c?

There are two kinds of expressions in Objective-C

1. RValue 

 The term rvalue refers to a data value that is stored at some address in memory

2. LValue

Expressions that refer to a memory location is called "lvalue" expression. An lvalue may appear as either the left-hand or right-hand side of an assignment

I didn't get it . can someone explain it to me?

Solution

  • RValue is a value that is evaluated but does not have a designated memory address to be stored until assigned to such a memory location. For example :

    5 * 2 is an expression evaluated to the number 10. This evaluated expression is still not assigned to a memory address (only a temporary one used for the calculation but you cannot directly refer to it) and will be lost if not stored. And this is the role of the LValue to provide a memory location to store the evaluated expression :

    int x;
x = 5 * 2;

    Here x refers to a certain memory address and the calculated number (10) can now be stored where x refers to (i.e. in the memory space assigned to x) via the assignment operator. So in the example above x is the LValue and the expression 5 * 2 is the RValue