Re: [Boost-bugs] [Boost C++ Libraries] #5689: lexical_cast must understand "inf" and "nan"

Subject: Re: [Boost-bugs] [Boost C++ Libraries] #5689: lexical_cast must understand "inf" and "nan"
From: Boost C++ Libraries (noreply_at_[hidden])
Date: 2012-02-16 17:24:44

#5689: lexical_cast must understand "inf" and "nan"
--------------------------------------+-------------------------------------
  Reporter:  apolukhin                |       Owner:  apolukhin      
      Type:  Support Requests         |      Status:  reopened       
 Milestone:  Boost 1.48.0             |   Component:  lexical_cast   
   Version:  Boost Development Trunk  |    Severity:  Regression     
Resolution:                           |    Keywords:  inf nan fininte
--------------------------------------+-------------------------------------
Changes (by apolukhin):

 * cc: antoshkka@… (added)
  * status:  closed => reopened
  * resolution:  fixed =>
  * type:  Bugs => Support Requests

Comment:

 Replying to [comment:5 anonymous]:
 > using 1.48 version of lexical_cast works for "nan" but throws a error
 for "NaN". I do not think there is a formal specification for Not-A-Number
 in string form, but "NaN" is a common usage form.[[BR]]

 There is a formal specification for Not-A-Number strings. According to
 standatd strtod, strtof, and strtold, scanf, sscanf and fscanf functions
 must parse NaN like that:
 {{{
 The expected form of the subject sequence is an optional plus or minus
 sign, then one of
 the following:
 — INF or INFINITY, ignoring case
 — NAN or NAN(n-char-sequenceopt), ignoring case in the NAN part, where:
 ...
 }}}
 [[BR]]
 Last time I`ve been confused by printf functions, they have more strict
 rules for outputting NaNs:
 {{{
 A double argument representing an infinity is converted in one of the
 styles
 [-]inf or [-]infinity — which style is implementation-defined. A
 double argument representing a NaN is converted in one of the styles
 [-]nan or [-]nan(n-char-sequence) — which style, and the meaning of
 any n-char-sequence, is implementation-defined. The F conversion specifier
 produces INF, INFINITY, or NAN instead of inf, infinity, or nan,
 respectively.
 }}}[[BR]]
 [[BR]]
 Great thanks for reporting this bug![[BR]]

-- 
Ticket URL: <https://svn.boost.org/trac/boost/ticket/5689#comment:6>
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