On Fri, Oct 08, 2010 at 11:04:59PM +0200, Karl Hammar wrote: > > Please, I was commenting about the misunderstandings about > "floating-point", not about mils and mm's. > > With integer types you get aliasing artifacts, which actually is a > rounding error. We have this problem in the current incarnation of pcb. > > So, in what way are floats worse than ints (I'm talking about > representaion, not about performance) and why could we not "reasonably > use floating-point"? >
The concern is with /binary/ floating point, not floating point in general. In binary floating point, your scale is always a power of 2, so some numbers cannot be represented - particularly, some numbers cannot be represented that /can/ be represented in decimal (like 0.3), so we will introduce an error when somebody types .3 into pcb. With integers, anything the user can type, can be represented. Importantly, 1/254 = 1/2 * 1/127 cannot be represented in binary floating point, which brings us back to the mm/mil problem. This is the crucial difference between our scaling idea (fundamental units + an arbitrary multiplier) and binary floating point. Andrew _______________________________________________ geda-user mailing list geda-user@moria.seul.org http://www.seul.org/cgi-bin/mailman/listinfo/geda-user