[boost] Re: A question about static_log2

From: Gennaro Prota (gennaro_prota_at_[hidden])
Date: 2003-01-20 18:36:35

On Mon, 20 Jan 2003 19:40:42 +0100, Gennaro Prota
<gennaro_prota_at_[hidden]> wrote:

>>  enum {c = (1 << n) <= x};
>
>
>Wrong. The left-shift may give undefined behavior, because n can be
>greater than or equal to the number of value bits in an unsigned long
                                                         ^^^^^^^^^^^^^

In an int, sorry. I was thinking to the case below

>>  enum {value = c*n + log2<(x>>(c*n)),(n/2)>::value};

where the left operand of >> has, of course, type unsigned long.

Genny.