What does &= mean in objective c?
I ran into this bit of code today:
indexValid &= x >= 0;
What does the &= mean? Could someone explain what is occurring in this statement?
This is not about Objective-C, but regular C.
Here the statement with the &= operator is equivalent to indexValid = indexValid & (x >= 0) . The & operator itself is called the bitwise and operator, and AND s the operands. Which means, returns 1 only if both operands are 1 , else returns 0 if any of the operands is not 1 . AND ing and OR ing is commonly used in setting flags in software.
For example, if indexValid is 0011010 in binary and you AND it with (x >= 0) (which is a boolean expression result, either 1 or 0), the result is 0000000 and (let's say x >= 0 evaluates to 1) as 0011010 & 0000001 evaluates to 0000000 .
If you don't know about binary logic, http://en.wikipedia.org/wiki/Boolean_logic is a good source to start.
It is the bitwise AND plus assignment operator (or 'and accumulate').
It combines a bitwise AND against the left-hand operand with assignment to said operand.
x&= y;
is
x= x & y;
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