Operator precedence determines the grouping of terms in an expression. This affects how an expression is evaluated. Certain operators have higher precedence than others; for example, the multiplication operator has higher precedence than the addition operator.
For example x = 7 + 3 * 2; here, x is assigned 13, not 20 because operator * has higher precedence than +, so it first gets multiplied with 3*2 and then adds into 7.
Here, operators with the highest precedence appear at the top of the table, those with the lowest appear at the bottom. Within an expression, higher precedence operators will be evaluated first.
|Logical NOT and negative sign||.not. (-)||Left to right|
|Exponentiation||**||Left to right|
|Multiplicative||* /||Left to right|
|Additive||+ -||Left to right|
|Relational||< <= > >=||Left to right|
|Equality||== /=||Left to right|
|Logical AND||.and.||Left to right|
|Logical OR||.or.||Left to right|
|Assignment||=||Right to left|
Try the following example to understand the operator precedence in Fortran −
program precedenceOp ! this program checks logical operators implicit none ! variable declaration integer :: a, b, c, d, e ! assigning values a = 20 b = 10 c = 15 d = 5 e = (a + b) * c / d ! ( 30 * 15 ) / 5 print *, "Value of (a + b) * c / d is : ", e e = ((a + b) * c) / d ! (30 * 15 ) / 5 print *, "Value of ((a + b) * c) / d is : ", e e = (a + b) * (c / d); ! (30) * (15/5) print *, "Value of (a + b) * (c / d) is : ", e e = a + (b * c) / d; ! 20 + (150/5) print *, "Value of a + (b * c) / d is : " , e end program precedenceOp
When you compile and execute the above program it produces the following result −
Value of (a + b) * c / d is : 90 Value of ((a + b) * c) / d is : 90 Value of (a + b) * (c / d) is : 90 Value of a + (b * c) / d is : 50