st: precision problem using double

[Leandro Brufman <leandrobrufman@gmail.com>]

Been reading some stuff on the precision of double, and how Stata
reads numbers for calculation (in particular this article
http://www.stata-journal.com/sjpdf.html?articlenum=dm0022)
But couldn't find a solution. Here's my problem:

sum  spread
br if spread==`r(max)'

* it returns that there are no observations.

sum spread
br if spread-`r(max)'<smallestdouble()

*it also returns that there are no observations

sum  spread
gen test=spread-`r(max)'

* the minimum number of variable test is -2.84217094e-14

any ideas on how to fix this code? i don't need a lot of precision,
but I do need to have these two lines working fine:
sum  spread
br if spread==`r(max)'


as usual, many many thanks in advance...
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