What is an arithmetic IF in FORTRAN programming?

Answer 1

Unlike a logical IF where the control expression is Boolean and has two branches depending on whether the expression evaluates true or false, the control expression of an arithmetic IF is a numeric expression (such as x+y) and has three branches depending on whether that expression evaluates negative, zero or positive.

In languages that do not provide native support for arithmetic IF (such as C++), we can implement arithmetic IF using logical IF as follows, where z holds the result of the arithmetic expression (such as z=x+y):

if (z<0) {

// negative path

} else if (z==0) {

// zero path

} else {

// positive path

}