C Language Operators
Introduction
An operator in a programming language is a symbol that tells the compiler or interpreter to perform a specific mathematical, relational or logical operation and produce a final result.
C has many powerful operators.
Many C operators are binary operators, which means they have two operands. For example, in a / b, / is a binary operator that accepts two operands (a, b).
There are some unary operators which take one operand (for example: ~, ++),
and only one ternary operator ? :.
Syntax
- expr1 operator
- operator expr2
- expr1 operator expr2
- expr1 ? expr2 : expr3
Remarks
Operators have an arity, a precedence and an associativity.
-
Arity indicates the number of operands. In C, three different operator arities exist:
- Unary (1 operand)
- Binary (2 operands)
- Ternary (3 operands)
-
Precedence indicates which operators "bind" first to their operands. That is, which operator has priority to operate on its operands. For instance, the C language obeys the convention that multiplication and division have precedence over addition and subtraction:
a * b + cGives the same result as
(a * b) + cIf this is not what was wanted, precedence can be forced using parentheses, because they have the highest precedence of all operators.
a * (b + c)This new expression will produce a result that differs from the previous two expressions.
The C language has many precedence levels; A table is given below of all operators, in descending order of precedence.
Precedence Table
Operators Associativity ()[]->.left to right !~++--+-*(dereference)(type)sizeofright to left *(multiplication)/%left to right +-left to right <<>>left to right <<=>>=left to right ==!=left to right &left to right ^left to right |left to right &&left to right ||left to right ?:right to left =+=-=*=/=%=&=^=|=<<=>>=right to left ,left to right -
Associativity indicates how equal-precedence operators binds by default, and there are two kinds: Left-to-Right and Right-to-Left. An example of Left-to-Right binding is the subtraction operator (
-). The expressiona - b - c - dhas three identical-precedence subtractions, but gives the same result as
((a - b) - c) - dbecause the left-most
-binds first to its two operands.An example of Right-to-Left associativity are the dereference
*and post-increment++operators. Both have equal precedence, so if they are used in an expression such as* ptr ++, this is equivalent to
* (ptr ++)because the rightmost, unary operator (
++) binds first to its single operand.
