Parameter containing ratio not evaluated correctly

[patrik-web]

I'm doing some arc length calculations and am running into problems:

I have two parameters: "length = 1"" and "radius = 2"".

Now I want to calculate a third parameter that is the remainder of a 90-degree angle after this arc. I add a new parameter 

"remainder", set the unit to angle/deg and enter the expression "90 deg - 1 rad * (length / radius)". The answer should be 90 deg - 1 rad * 0.5 or about 90 - 57/2 = 58.5 degrees. However, when I hit enter in the expression window, it is replaced by "90 deg - 1 rad mm / mm", or 32.7 degrees. The factor 1/2 from the ratio of the two lengths is missing.

I was under the impression that the expression calculator should be able to handle ratios resulting in unitless numbers. Is that not the case, or is this a bug in the code? It's in any case pretty bad that it does not give an error but just silently substitutes an incorrect result.

[lucasproko · Accepted solution]

Hey @patrik-web,

I'm sorry you're running into this issue. I was just able to recreate the situation on my computer using the same steps you described. I'm guessing this is a bug in our system, but I will follow up with a few of my colleagues to see what exactly causes this behavior. In the meantime, there is a work around if you create an additional parameter to hold the unitless value, and then use that parameter in your calculation as you see below.

Hopefully that helps a little bit, but thank you for pointing this out!

[patrik-web]

Ok, that's a decent workaround... as long as you notice the result being wrong in the first place. 😉