How do I best initialize a D double to an exact mantissa and exponent representation?

I'm specifically interested in

    2^^i for all i in [min_exp, max_exp]

On Tuesday, 17 January 2017 at 00:08:24 UTC, Nordlöw wrote:
> How do I best initialize a D double to an exact mantissa and exponent representation?
>
> I'm specifically interested in
>
>     2^^i for all i in [min_exp, max_exp]

This mach module can do the job: https://github.com/pineapplemachine/mach.d/blob/master/mach/math/floats/inject.d

On Tuesday, 17 January 2017 at 00:08:24 UTC, Nordlöw wrote:
> How do I best initialize a D double to an exact mantissa and exponent representation?
>
> I'm specifically interested in
>
>     2^^i for all i in [min_exp, max_exp]

See

std.bitmanip : FloatRep , DoubleRep;

On Tuesday, 17 January 2017 at 00:08:24 UTC, Nordlöw wrote:
> How do I best initialize a D double to an exact mantissa and exponent representation?
>
> I'm specifically interested in
>
>     2^^i for all i in [min_exp, max_exp]

If it doesn't have to be D ;), it can be as simple as `core.stdc.math.ldexp(1, exponent)`. No CTFE though.

On Tuesday, 17 January 2017 at 16:40:57 UTC, kinke wrote:
> If it doesn't have to be D ;), it can be as simple as `core.stdc.math.ldexp(1, exponent)`. No CTFE though.

Isn't it a simple as

    2.0^^exponent

?

On Tuesday, 17 January 2017 at 17:56:13 UTC, Nordlöw wrote:
> On Tuesday, 17 January 2017 at 16:40:57 UTC, kinke wrote:
>> If it doesn't have to be D ;), it can be as simple as `core.stdc.math.ldexp(1, exponent)`. No CTFE though.
>
> Isn't it a simple as
>
>     2.0^^exponent
>
> ?

It should and I looked into that as well, but I didn't like the implementation as loop: https://github.com/dlang/phobos/blob/master/std/math.d#L5988

A special case for base x == 2 wouldn't hurt.

On Tuesday, 17 January 2017 at 18:25:46 UTC, kinke wrote:
> It should and I looked into that as well, but I didn't like the implementation as loop: https://github.com/dlang/phobos/blob/master/std/math.d#L5988
>
> A special case for base x == 2 wouldn't hurt.

That seems strange. Why isn't that a builtin behaviour for operator ^^?