C++ PATCH: Disallow floating-point literals in integral-constant expressions

[Marcin Dalecki]

On 2005-02-02, at 05:52, Gabriel Dos Reis wrote:

> Joe Buck <Joe.Buck@synopsys.COM> writes:
>
> | On Tue, Feb 01, 2005 at 12:16:14PM -0800, Mark Mitchell wrote:
> | > My thinking is that we've been disallowing template parameters of
> | > floating-point type for a while now.  If we really want to allow
> | > constant expressions of floating-point type forever more, we ought 
> to
> | > also allow template parameters of floating-point type as well.
> |
> | I would argue against allowing template parameters of floating-point
> | type, because you get two distinct functions instead of one because
> | of rounding errors: func<1.0> vs func<0.9999999999999>.
>
> Not that I'm a fan of that extension, but I'm not convinced by that
> argument.  How is it different from
>
>     func<some-integer-value>

Expressed in terms of formal logic: The main difference is that for 
floating point values the
model as given by a CPU is only a homology and not an ontology.
Or bluntly speaking - there are multiple different bit patterns, which 
can represent the
same floating point value, like for example 0.1 == 1.0e-1. Think about 
it and
how templates generate code...