Duel wield/double attack percentages/code? (warning: mathy)

[Splorf22]

IIRC warriors and rangers dual wield with skill+level / 500. At L60 this is 60% for warriors. So for example:

SCD 10/18 dmg bonus 11 -> 31/18 = 1.72
Wurmslayer 25/40 -> 50*0.6 / 40 = 0.75
total -> 2.47

Staff of Battle 31/37 damge bonus 17 -> 79/37 = 2.13

Of course the calculation is not that simple, because it depends on str/atk (higher = bigger max hits, so ratio is more important than damage bonus), level (higher = more dw chance and more 2HB bonus), triple attack for warriors only applies to the mainhand, etc.