The following SVG path can draw 99.99% of a circle: (try it on http://jsfiddle.net/DFhUF/46/ and see if you see 4 arcs or only 2, but note that if it is IE, it is rendered in VML, not SVG, but have the similar issue)

M 100 100 a 50 50 0 1 0 0.00001 0

But when it is 99.99999999% of a circle, then nothing will show at all?

M 100 800 a 50 50 0 1 0 0.00000001 0    

And that's the same with 100% of a circle (it is still an arc, isn't it, just a very complete arc)

M 100 800 a 50 50 0 1 0 0 0 

How can that be fixed? The reason is I use a function to draw a percentage of an arc, and if I need to "special case" a 99.9999% or 100% arc to use the circle function, that'd be kind of silly.

Again, a test case on jsfiddle using RaphaelJS is at http://jsfiddle.net/DFhUF/46/
(and if it is VML on IE 8, even the second circle won't show... you have to change it to 0.01)

Update:

This is because I am rendering an arc for a score in our system, so 3.3 points get 1/3 of a circle. 0.5 gets half a circle, and 9.9 points get 99% of a circle. But what if there are scores that are 9.99 in our system? Do I have to check whether it is close to 99.999% of a circle, and use an arc function or a circle function accordingly? Then what about a score of 9.9987? Which one to use? It is ridiculous to need to know what kind of scores will map to a "too complete circle" and switch to a circle function, and when it is "a certain 99.9%" of a circle or a 9.9987 score, then use the arc function.