[Bug v257-20] Decimal addition/comparison problem

[AyreGuitar]

I doubt this is something new in the latest beta, but thought I'd share it here anyway.

Seems there's some problems when comparing decimal values.

I've attached a simple file to show the problem.

Looks like it's similar to this post:
http://community.clickteam.com/threads/66111-Decimal-comparison-not-returning-true

Would appreciate a workaround that handled more general cases correctly every time (other than not using decimals in the first place!)

[AyreGuitar]

Thanks for the suggestion, SilentBob92PL.
This works for the 3 tests in my example file. Unfortunately, not so good for more general values, eg If I want to start at 0.2, decrease by 0.05 each time and stop at when <=0, I get:

0.15
0.1
0.05
1.38778e-17
-0.05

Similar problems with other subtraction values, eg 0.1, 0.2
In fact subtractiosn (or negative increments) seem much worse than adding for getting these kind of problem values.

I guess it's just better to use integers for such stuff and divide by 100.0 later?

[DistantJ]

This is weird, I'm wondering if this is what's breaking my platform engine (based on Nifflas' one). Nifflas' own platform engine seems broken now too. Moving left seems to now move the character to the right, and sometimes he shoots across the screen. Also the jump is broken now.

[AyreGuitar]

DistantJ - I doubt it's related, since this happened before Beta257-22 and gives same results as before after installing this Beta.

[ouly]

Usually it's recommended to avoid comparing directly float number with another float number but instead to check if the difference between the two float number is under a specific threshold.

It has nothing to do with MMF but it's just due to the way float number are encoded and handled on computers.

Have a look to http://www.parashift.com/c++-faq/flo...int-arith.html

[AftPeakTank]

Nice one ouly!