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Expressions - Returning a number when using a length

leecaseyleecasey Member Posts: 36 PRO
in Using Onshape
Hi I'm having a bit of trouble generating an integer for a pattern number from an expression which is using an length (mm). 

floor((#length/2)/60)

I'm assuming the issue is incompatible types but not sure how to solve it. Is there any way to cast #length as an int? 

Comments

  • S1monS1mon Member Posts: 3,298 PRO
    You can divide by 1 mm to get rid of the units, but I'm a little unclear how you're trying to use this calculation.

    I didn't test this, but something like this should work:
    floor((#length/2)/60)/(1 mm)

    If you ever change the units of the document it's going to break, and I can't quickly think of a way to make this so that it will just get rid of the units in a universal way.
  • _anton_anton Member, Onshape Employees Posts: 436
    Simon is correct. FWIW, though, I'd flip the logic around: make a variable like #number_of_instances, then make a #length variable computed from that. That makes it easy to update things and saves you from having to floor() anything.
  • S1monS1mon Member Posts: 3,298 PRO
    You might also want to look at Linear Pattern Plus. It might solve your needs without needing to write any expressions.

    https://forum.onshape.com/discussion/18076/new-feature-linear-pattern-plus/p1

  • leecaseyleecasey Member Posts: 36 PRO
    Unfortunately that didn't work. Here's a better explanation of what I'm trying to achieve. I need to pattern some holes on this rail, the pattern must be central to the rail, hence why I'm dividing the length by 2. So I just want to generate the number of holes in the pattern from the length in mm. 
  • leecaseyleecasey Member Posts: 36 PRO
    Thank you, the above didnt work but a little change of parenthesis did the job! 

    floor(#length/2/60/(1mm)) 
  • NeilCookeNeilCooke Moderator, Onshape Employees Posts: 5,845
    You also don’t need the “1” - just “mm” will do. 
    Senior Director, Technical Services, EMEA
  • EvanReeseEvanReese Member, Mentor Posts: 2,349 ✭✭✭✭✭
    This is exactly the kind of situation I wrote Linear Pattern Plus for (as Simon mentioned). in your case, is the 60 the hole spacing? if so, you could also just make it 60mm and that'd do it. length/length = number
    Evan Reese
    Independent Onshape Consultant
  • leecaseyleecasey Member Posts: 36 PRO
    Thanks everyone. 👍 will certainly check out LPP, Evan. 🙂
  • vanowmvanowm Member Posts: 30 ✭
    https://forum.onshape.com/discussion/comment/91300#Comment_91300

    Can someone please explain this nonsense? dividing length by a number = length, dividing length by a length = number? WTF?

  • EvanReeseEvanReese Member, Mentor Posts: 2,349 ✭✭✭✭✭

    Think of units as something that can be divided out. mm/mm = 1 and in/mm = 25.4

    Since #length has units in it already, to get a number for the floor function, you have to divide by units. So if #length = 5mm you could get just 5 with #length/mm = 5

    Evan Reese
    Independent Onshape Consultant
  • vanowmvanowm Member Posts: 30 ✭
    https://forum.onshape.com/discussion/comment/116598#Comment_116598

    That is actually a brilliant explanation. Thank you!

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