Description |
 |
The usual arithmetic conversions are performed on the operands
if both have arithmetic type. Both operands must be arithmetic,
or both operands must be pointers to the same type, or one operand
can be a pointer and the other a null pointer constant or a pointer
to void.
Both of the operators == (equal) and
!= (not equal) yield 1 if the specified relation
is true; otherwise they will yield 0. The result is of type int
and is not an lvalue.
The ==
and != operators
are analogous to the relational operators except for their lower
precedence. This means that the expression a<b==c<d
is true if and only if a<b
and c<d have
the same truth value.
Use caution with the ==
operator. It resembles the assignment operator (=)
and is often pronounced the same when programs are read. Further,
you can use the ==
operator in expressions syntactically the same as you would the
= operator. For
example, the statements
if(a==b) return 0;
if(a=b) return 0; |
look very much alike, but are very different. The first statement
says "if a is
equal to b, return
a value of zero." The second statement says "store b
into a and if
the value stored is nonzero, return a value of zero."
