How to use a pre-defined variable as an argument inside a math function?

john270

I've been struggling to figure out how to use a pre-defined variable as an argument inside a math function such as floor(x) or ceil(x).  I can get a real number to work fine as the argument, but every time I use a variable expression such as floor(#length) where the #length has been previously given a decimal real number value through a configuration table, it returns with the error of "Invalid Expression".  Yet I see instructions to do this very thing in several Learning Center videos.  Am I missing a correct syntax format to do this?  I just can't find any documentation of how to use the variables inside functions.  I would appreciate the help.

ilya_baran

The problem is that you can't take the floor or ceiling of a length, only a number.  (This is because the floor of a length in inches is different than in meters; if we were to use document units, then changing units would change the design, which is undesirable).  The way to do this computation, if the units you care about are inches is:
floor(#length / in) * in
The division converts the length into a number of inches, and the multiplication converts the floored result back to a length.

john270

Yes, thank you for your response. I now realize I need to divide by "in" to get it unitless.  I didn't realize that since I was using that variable as a length for a part, that it carried the units with it.  I was assuming it got treated like "number" in the variable type choices.  I understand now.