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From: "Malcolm Cohen" <malcolm@nag-j.co.jp>
To: "WG5" <sc22wg5@open-std.org>
References: <20140702232501.1F2EE35877B@www.open-std.org><Prayer.1.3.5.1407031114370.31488@hermes-1.csi.cam.ac.uk><20140703175703.0B23F3587E3@www.open-std.org> <20140703194324.CB8E9358758@www.open-std.org>
In-Reply-To: <20140703194324.CB8E9358758@www.open-std.org>
Subject: Re: [ukfortran] (SC22WG5.5300)   Did we intend to prohibit this?
Date: Fri, 4 Jul 2014 09:37:12 +0900
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>  integer, parameter :: RK = kind(1.0e0)
>  real(rk), parameter :: SNaN = merge( IEEE_Value(1.0_rk,IEEE_Signaling_NaN), &
>                                     & 0.0_rk, IEEE_Support_DataType(1.0_rk) )

This would in any case not be conforming when either IEEE_SUPPORT_DATATYPE is 
false or IEEE_SUPPORT_NAN is false, since MERGE is not "short-cut" evaluation.

There are many traps and pitfalls associated with trying to use signalling NaN 
in user code, especially in code that might be evaluated at compile-time.  I 
would not recommend embarking on such a journey.

Cheers,
-- 
................................Malcolm Cohen, Nihon NAG, Tokyo.