10.7 Increment Operators

Increment operators increase or decrease the value of a variable by 1. The operator to increment a variable is written as `++'. It may be used to increment a variable either before or after taking its value.

For example, to pre-increment the variable x, you would write ++x. This would add one to x and then return the new value of x as the result of the expression. It is exactly the same as the expression x = x + 1.

To post-increment a variable x, you would write x++. This adds one to the variable x, but returns the value that x had prior to incrementing it. For example, if x is equal to 2, the result of the expression x++ is 2, and the new value of x is 3.

For matrix and vector arguments, the increment and decrement operators work on each element of the operand.

Here is a list of all the increment and decrement expressions.

++x

This expression increments the variable x. The value of the expression is the new value of x. It is equivalent to the expression x = x + 1.

--x

This expression decrements the variable x. The value of the expression is the new value of x. It is equivalent to the expression x = x - 1.

x++

This expression causes the variable x to be incremented. The value of the expression is the old value of x.

x--

This expression causes the variable x to be decremented. The value of the expression is the old value of x.

It is not currently possible to increment index expressions. For example, you might expect that the expression v(4)++ would increment the fourth element of the vector v, but instead it results in a parse error. This problem may be fixed in a future release of Octave.