------- Comment #3 from burnus at gcc dot gnu dot org  2010-03-09 07:24 -------
Quoting the standard. Note especially that also "NaN(optional)" is valid:

"(1) On input, leading blanks are not significant. When the input field is not
an IEEE exceptional specification (10.6.1.2.1), the interpretation of blanks,
other than leading blanks, is determined by the blank interpretation mode
(10.7.6)." [F2003, 10.6.1, (1)]

"An input field that is an IEEE exceptional specification consists of optional
blanks, followed by either of
(1) an optional sign, followed by the string ’INF’ or the string ’INFINITY’ or
(2) an optional sign, followed by the string ’NAN’, optionally followed by zero
or more alphanumeric characters enclosed in parentheses," [F2003, 10.6.1.2.1]


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=43298