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Re: RFC [Patch, Fortran] PR - support "q" for exponents when READing floating-point numbers

From: Tobias Burnus <burnus at net-b dot de>
To: gcc patches <gcc-patches at gcc dot gnu dot org>, gfortran <fortran at gcc dot gnu dot org>
Date: Fri, 20 Apr 2012 11:34:58 +0200
Subject: Re: RFC [Patch, Fortran] PR - support "q" for exponents when READing floating-point numbers
References: <4F9129E5.30002@net-b.de>

Small follow up.

On 04/20/2012 11:18 AM, Tobias Burnus wrote:

Testing other compilers, the result is:
- 'q' not supported: g95, NAG f95, PGI, PathScale, Crayftn
- 'q' supported: g77, ifort, sunf95

It seems to be also supported by IBM's xlf - at least it supports such literals in the source code. (Cf. [1].)

Before Fortran 90, using "q" was to only way to write quad precision literals in the source code. For I/O, it does not matter. However, some compilers wrote "d" for double precision - newer compilers prefer "e" and accept both "e" and "d" as input, in line with the standard. It is unclear whether some compilers also wrote "q" for the output or whether just users did/do so - either because they are used to it, or under the (always or only nowadays?) wrong perception that it matters.

Tobias

[1] http://publib.boulder.ibm.com/infocenter/lnxpcomp/v9v111/index.jsp?topic=/com.ibm.xlf111.linux.doc/xlflr/realdatatype.htm

References:
- RFC [Patch, Fortran] PR - support "q" for exponents when READing floating-point numbers
  - From: Tobias Burnus

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