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Assignment Operators
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Syntax
unaryexpression assignmentop assignmentexpression
Remarks
The assignment operators are:
= *= /= %= += = <<= >>= &= ^= =
The = operator is the only simple assignment operator, the others are compound assignment operators.
In the expression E1 = E2
, E1
must be a modifiable lvalue. The assignment expression itself is not an lvalue.
The expression
E1 op= E2
has the same effect as
E1 = E1 op E2
except the lvalue E1
is evaluated only once. For example, E1 += E2
is the same as E1 = E1 + E2
.
The expression's value is E1
after the expression evaluates.
For both simple and compound assignment, the operands E1
and E2
must obey one of the following rules:

E1
is a qualified or unqualified arithmetic type andE2
is an arithmetic type. 
E1
has a qualified or unqualified version of a structure or union type compatible with the type ofE2
. 
E1
andE2
are pointers to qualified or unqualified versions of compatible types, and the type pointed to by the left has all the qualifiers of the type pointed to by the right.  Either
E1
orE2
is a pointer to an object or incomplete type and the other is a pointer to a qualified or unqualified version of void. The type pointed to by the left has all the qualifiers of the type pointed to by the right. 
E1
is a pointer andE2
is a null pointer constant.
Note: Spaces separating compound operators (+
<space>=
) will generate errors.
Note: There are certain conditions where assignment operators are not supported when used with properties.