blitz3d and floats - strange problem

Just messing around with some code in my game and getting some strange results, so to investigate I simplified the code and STILL got weird results.

value# = 1000

For loop = 1 to 25

print value#
if value# >=0.1
value# = value# - 0.1
end if

Next

Now I'd expect for each loop, I'd get values like 1000, 999.9, 999.8 and so on...

Can someone explain why its goes...

998.1
998.0
997.901
997.801

It's a little scary I admit, but it is not uncommon. I tested your code on this pc and it does the same. All I can say is that maybe the Blitz products can not be relied upon for 100% accurate floating point maths. However as I mainly use floats for 3D stuff, it doesn't tend to need to be 100% accurate so I'm happy to let little things like this go.

inaccuracies in floating point math
and
Blitz likes to only retain the six most significant digits when converting a float to a string or integer (which it's doing when you print it)

are there any commands that can round the number from 997.901 to 997.9 ?

Notice what happens if you do this instead:

value# = 1000 

For loop = 1 To 25 
	Print value# 
	If value# >=0.1
		;value# = value# - 0.1 
		value# = value# * 10
		value# = value# - 1
		value# = value# / 10.0
	End If 
Next 

WaitKey

Use ints and divide by 10.

does divide by 10 use much processor time ?

nope