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# ceil() misbehaving

Member, csevp Posts: 55 PRO
I'm trying to round up a value but:
1. ceil(1) or ceil(1,1) return 1 and roundToPrecision(2,0) returns 2 as expected.
2. ceil((2405mm-1200mm)/(1200mm+5mm),1) returns 2 ??
3. roundToPrecision((2405mm+5mm)/(1200mm+5mm),0) returns 3 ??
Please tell me what I am doing wrong here!

• Member, Onshape Employees Posts: 271
#2 is because ((2405mm-1200mm)/(1200mm+5mm) is equal to slightly more than 1 because of floating-point math, and the ceil(..., 1) rounds it up to the next multiple of 1, which is 2.

For #3, I'm getting 2.
• Moderator, Onshape Employees Posts: 5,354
Yes, everything is stored in meters.
Senior Director, Technical Services, EMEAI

• Member, Onshape Employees Posts: 271
#2 is because ((2405mm-1200mm)/(1200mm+5mm) is equal to slightly more than 1 because of floating-point math, and the ceil(..., 1) rounds it up to the next multiple of 1, which is 2.

For #3, I'm getting 2.
• Member, csevp Posts: 55 PRO
Okay I think what really gets me is that adding 5mm to 1200mm is where the error begins. This seems like it shouldn't happen even with rounding error. From what I've seen onshape uses IEEE standard 64 bit floating arithmatic.

According to this link https://www.h-schmidt.net/FloatConverter/IEEE754.html I can see that I shouldn't have errors unless rather then FS units storing values with units as milimeters it actually stores them as meters. In other words 1200mm in the value with units type map is stored as 1.200 and units is meter.

This seems to be consistant as I've tested it with a couple FS scripts:
annotation { "Feature Type Name" : "SUM Print" }
export const PrintMe = defineFeature(function(context is Context, id is Id, definition is map)
precondition
{
annotation { "Name" : "X" }
isLength(definition.X, LENGTH_BOUNDS);

annotation { "Name" : "Y" }
isLength(definition.Y, LENGTH_BOUNDS);
}
{
var X = definition.X;
var Y = definition.Y;
println(X+Y);
});

annotation { "Feature Type Name" : "ADDfix Print" }
export const PrintMeADDfix = defineFeature(function(context is Context, id is Id, definition is map)
precondition
{
annotation { "Name" : "X" }
isLength(definition.X, LENGTH_BOUNDS);

annotation { "Name" : "Y" }
isLength(definition.Y, LENGTH_BOUNDS);
}
{
var X = definition.X*1000;
var Y = definition.Y*1000;
println((X+Y)/1000);
});

/*
results in:
1.2049999999999998 meter
1.205 meter
when I enter 1200mm and 5mm as X and Y
*/

• Moderator, Onshape Employees Posts: 5,354