Re: [xml] Getting crazy with float parsing

[Bjorn Reese <breese mail1 stofanet dk>]

Daniel Veillard wrote:

> I cannot get xmlXPatythStringEvalNumber to read "39413.80" as such
> and not as 39413.800000000003 or some similary biased value, whatever
> trick I play.
>  Any idea ? Would trio handle this correctly (assuming the string has
> been first checked to be of the right format) ?

As Anthony and Aleksey already have pointed out, this is due to the
inherent inaccuracy of floating-point numbers. The link posted by
Aleksey describes the limitation in much detail.

The problem exposed by the bug report is that format-number() tries
to print more significant digits than can be represented by a double
(DBL_DIG, which usually is 15).

Although trio attempts to handle this situation (for example, it does
print 7/5 correctly, which my libc printf does not), it does not handle
all cases appropriately yet, and it also gets 39413.8 wrong. In fact,
this is an issue I have been looking at recently, but still haven't
found a solution for. If I do manage, I'll let you know.

>  this really drive me nuts,

Please allow me neutrality on the topic of your mental health ;)