Re: Slowness in bignum mode ( gmp | gawk -M ) when doubling extremely large inputs

[arnold]

<pjfarley3@earthlink.net> wrote:

> There are also several strange uses of the exclamation point operator
> (!) that I do not understand, but that is probably just my lack of
> experience.  Examples of such use are:
>
> _n1-!!_n1
> -!-""
> !+""
> !--_n10
>
> I THINK these are intended to be uses of the negation operator, but I
> don’t understand what that operation is supposed to do to an empty
> string.

Using ! converts non-zero to zero and zero to one, depending on the
value of the expression to which it is applied.

        !! <something>

converts <something> into a canonical truth value of 1 or 0. This can
occasionally be useful in C / C++ as well:

        const char *truth_value[] = { "false", "true" };

        printf("xyzzy is %s\n", truth_value[!! (some_expression)]);

Arnold