On 15 Nov 2009, at 00:42, Marnen Laibow-Koser wrote: > Eleanor McHugh wrote: >> On 14 Nov 2009, at 23:40, Marnen Laibow-Koser wrote: >>> It should be fairly clear from the formulae. One thing that bears >>> repeating, though: never use the default floating-point numbers for >>> math; they're simply not precise enough. Use integers or >>> BigDecimal. >> >> >> That rather depends on the required level of precision... >> > > Well, error accumulates pretty quickly in IEEE 754 floats, and > trajectories require lots of calculation. I wouldn't trust floats > in a > situation like that -- would you? In a hardcore physics simulation with many forces then no I wouldn't, but in a simple game then yes I'd probably go with floating-point :) Ellie Eleanor McHugh Games With Brains http://slides.games-with-brains.net ---- raise ArgumentError unless @reality.responds_to? :reason