Explanation of traveltime expression

[jdoran 1]

Math.If(Token.ReturnValue > 0.0, Size.Length / (Token.ReturnValue + (Token.ReturnValue == 0.0)), Infinity)

determines the EntityMovementRate on a timepath.

Can someone explain the "(Token.ReturnValue == 0.0)"?

Token.ReturnValue is equal to the time the entity will take to traverse the path, so I can see the inverse relationship of time and speed, but I do no understand the purpose of that sub expression. If my thinking is correct, it will always evaluate to 0. If the IF statement somehow broke, only then would it evaluate to 1.

 

[gdrake 1]

I think that expression was simply originally coded that way to avoid any possibility of a Divide By Zero error, because the Math.If function in early Simio versions was evaluating every argument.

However, I think now the Math.If only evaluates an argument in the expression if it has to, so possibly that TimePath expression could be simplified to remove that '+ (Token.ReturnValue==0.0)' stuff.

Regardless, it is of course harmless coded as is.

[jdoran 1]

Thanks Glenn. It is certainly a more compact way of correcting for zero, than what I usually do. I will have to keep this trick in mind.