Make a Variable Negative in PlayBasic

How to Make the Value of a Variable Negative in PlayBasic

Making the value of a variable negative involves two steps :

1. Check if the variable is positive.
2. Change the number from a positive number to a negative number.

There's two ways to check whether the variable is positive, with the first being slightly better. The number is actually converted into a negative number by Neg()

Making a Variable Negative with Abs( )

Abs() converts a negative number into a positive number. If the number is already positive, it does nothing. This allows you to check if the variable is positive by comparing the variable itself with the result of the variable when Abs() is used on it.

If someVar = Abs(someVar) Then someVar = Neg(someVar)

Complete Code

ForceDeclaration

Declaration
    someVar
EndDeclaration

someVar = 10

If someVar = Abs(someVar) Then someVar = Neg(someVar)

Print someVar
WaitKey

Making a Variable Negative with GetSign( )

If a number is positive, GetSign() returns a 0. Therefore, you can check it to see if the number is positive.

If GetSign(someVar) = 0 Then somevar = Neg(someVar)

If you are a BASIC programmer and find this strange, yes, you're right. In most BASIC dialects, Sgn() returns 1 for a positive number. Not PlayBasic. It returns a 0 for both 0 and positive numbers.

Complete Code

Declaration
    someVar
EndDeclaration

someVar = 42

If GetSign(someVar) = 0 Then somevar = Neg(someVar)

Print someVar
Sync
WaitKey