It seems almost all edit boxes used in PCB layout accept an equation (including sin, cos, pi, etc) as input that is calculated and then stored as the calculated value. For example if you type in “1 + 1” it gets stored as “2” and shows up as “2” if you go to re-edit the property. I think this feature would be much more useful if the text you type in was stored verbatim along with the result for internal use by the layout engine.
I’ve used equations a lot when e.g laying out equally spaced holes or pads. When I go back to edit the property, I’m just left with the result of the calculation. If I want to alter something, I need to remember what equation I used, and re-enter it. If the equation was saved you would only need to alter the term you want to change and save it.
Say you wanted to layout five equally spaced holes in a circle with a 4 unit radius. For the first hole you could enter: x: cos(2pi * 1/5) * 4, y: sin(2pi * 1/5) * 4, for the second hole: x: cos(2pi * 2/5) * 4, y: sin(2pi * 2/5) * 4 etc… If you later want to change the radius to 5 units, you just need to go in and change the 4 to a 5 instead of having to re-enter each equation again or keeping track of it elsewhere.
BONUS: It would be really great to have a table of named parameters that can be referenced by equations. That way you would be able to do something like “cos(2*pi * 1/5) * circle_radius” and only have to change the radius in one place instead of 5. The parameters themselves should also be able to be equations.
If you really just want e.g. “1 + 1” to be calculated and be stored as “2”, this could be handled e.g. by entering “=1 + 1”.