Has anybody cooked up some generic functions that extend `core.bitop` bitmanipulations to work on any value type?

Something like

    bool getBit(T)(in T a, int bitnum); // bt
    T setBit(T)(in T a, int bitnum); // bts
    auto ref setBitInPlace(T)(ref T a, int bitnum);

I know this is relatively easy to implement so that's why I'm curious to why its not already Phobos.

**Update:**

Here's my first try at this:

    /** Returns: $(D bitnum):th Bit Of $(D a).
        TODO: Why is this already in Phobos?
        TODO: Make this safe for integers
     */
    bool getBit(T, I)(in T a, I bitnum) @trusted pure nothrow if (isIntegral!I) {
        enum nBits = 8*T.sizeof;
        static      if (nBits ==  8) alias I = ubyte;
        else static if (nBits == 16) alias I = ushort;
        else static if (nBits == 32) alias I = uint;
        else static if (nBits == 64) alias I = ulong;
        immutable xi = (*(cast(I*)&a));
        immutable bitMask = ((cast(I)1 << bitnum));
        /* debug dln(eltIx, ",", bitnum, ",", xi, ",", bitMask); */
        return a & bitMask ? true : false;
    }
    alias bt = getBit;

My idea to make `getBit` work on all types that have value semantics. That's why I need the cast (I think). Is there a traits to check if a type has value semantics or not?

Also is there a trait to check if a type supports a specific operation such as bitwise and `&`? I could always use `__traits(compiles, ...)` but standardization is good.

To make it even better I guess I need an explicit overload for T's that support bit manipulations in order to make this variant @safe right? In my generic solution above I need the `cast` and that's @unsafe.

See also: https://stackoverflow.com/questions/21368664/manipulating-bits-of-any-value-type

On Sunday, 26 January 2014 at 20:56:29 UTC, Nordlöw wrote:

> My idea to make `getBit` work on all types that have value semantics.

All of them? Arbitrary structs too? floating point types? Static arrays? Might I ask... why do you need this sort of thing? :)

> That's why I need the cast (I think). Is there a traits to check if a type has value semantics or not?

The closest would be std.traits.hasIndirections.

> Also is there a trait to check if a type supports a specific operation such as bitwise and `&`? I could always use `__traits(compiles, ...)` but standardization is good.

No there isn't.

On Sunday, 26 January 2014 at 23:27:58 UTC, Stanislav Blinov wrote:
> On Sunday, 26 January 2014 at 20:56:29 UTC, Nordlöw wrote:
>
>> My idea to make `getBit` work on all types that have value semantics.
>
> All of them? Arbitrary structs too? floating point types? Static arrays? Might I ask... why do you need this sort of thing? :)

For bit-parallel run-length encoding for efficient serialization of sets of std.datetime:SysTime structures (16 bytes). I'm trying to differentially pack sets of SysTimes entries more efficiently because for a given directory containing files many of these files often share the majority of their bits. Meta-code:

foreach (n; 0..SysTime.sizeof)
  RLC all n-bits for all SysTimes

It is more an interesting experiment :)

>> That's why I need the cast (I think). Is there a traits to check if a type has value semantics or not?
>
> The closest would be std.traits.hasIndirections.

Does this work recursively on containing types?

>> Also is there a trait to check if a type supports a specific operation such as bitwise and `&`? I could always use `__traits(compiles, ...)` but standardization is good.
>
> No there isn't.

Thx.

On Sunday, 26 January 2014 at 23:37:40 UTC, Nordlöw wrote:

>> Might I ask... why do you need this sort of thing? :)
>
> For bit-parallel run-length encoding for efficient serialization of sets of std.datetime:SysTime structures (16 bytes).

SysTime's representation consists of a long and Rebindable!(immutable(TimeZone)). The latter is a struct containing a reference.

>> The closest would be std.traits.hasIndirections.
>
> Does this work recursively on containing types?

AFAIK no, it just checks immediate fields (if any).

On Sunday, 26 January 2014 at 23:54:02 UTC, Stanislav Blinov wrote:
> On Sunday, 26 January 2014 at 23:37:40 UTC, Nordlöw wrote:

>>> The closest would be std.traits.hasIndirections.
>>
>> Does this work recursively on containing types?
>
> AFAIK no, it just checks immediate fields (if any).

OTOH, it seems it does :)