How do I convert a double to a ubyte[]?

I've tried all sorts of things including converting the double to a ulong and trying to serialize the ulong. For example test bellow fails.

````
unittest {
    double d = 3.14;
    ulong l = *cast(ulong*)(&d);
    double after = *cast(double*)(&l));
    assert(after == d); // This fails.
}
````

On Thu, Dec 01, 2016 at 12:36:30AM +0000, Jake Pittis via Digitalmars-d-learn wrote:
> How do I convert a double to a ubyte[]?
> 
> I've tried all sorts of things including converting the double to a ulong and trying to serialize the ulong. For example test bellow fails.
> 
> ````
> unittest {
>     double d = 3.14;
>     ulong l = *cast(ulong*)(&d);
>     double after = *cast(double*)(&l));
>     assert(after == d); // This fails.
> }
> ````

	union U
	{
		ubyte[double.sizeof] bytes;
		double d;
	}
	U u, v;

	u.d = 3.14159;

	v.bytes[] = u.bytes[];
	assert(v.d == 3.14159);


T

-- 
Those who don't understand Unix are condemned to reinvent it, poorly.

On Thursday, 1 December 2016 at 00:36:30 UTC, Jake Pittis wrote:
> How do I convert a double to a ubyte[]?
>
> I've tried all sorts of things including converting the double to a ulong and trying to serialize the ulong. For example test bellow fails.
>
> ````
> unittest {
>     double d = 3.14;
>     ulong l = *cast(ulong*)(&d);
>     double after = *cast(double*)(&l));
>     assert(after == d); // This fails.
> }
> ````

That test passes for me, are you sure there isn't something else wrong with your code? Check to see if it works for just a ulong that has values in it's upper 32-bits?

On Thursday, 1 December 2016 at 00:36:30 UTC, Jake Pittis wrote:
> How do I convert a double to a ubyte[]?
>
> I've tried all sorts of things including converting the double to a ulong and trying to serialize the ulong. For example test bellow fails.
>
> ````
> unittest {
>     double d = 3.14;
>     ulong l = *cast(ulong*)(&d);
>     double after = *cast(double*)(&l));
>     assert(after == d); // This fails.
> }
> ````

platform, archi, compiler version ?

On Thursday, 1 December 2016 at 00:36:30 UTC, Jake Pittis wrote:
> How do I convert a double to a ubyte[]?
>
> I've tried all sorts of things including converting the double to a ulong and trying to serialize the ulong. For example test bellow fails.
>
> ````
> unittest {
>     double d = 3.14;
>     ulong l = *cast(ulong*)(&d);
>     double after = *cast(double*)(&l));
>     assert(after == d); // This fails.
> }
> ````

You could do something like below which will allow you to serialize any number.

````
import std.stdio : writeln;
import std.traits : isNumeric;

ubyte[] bytes(T)(T num) if (isNumeric!T) {
	auto buf = new ubyte[T.sizeof];
	
	(*cast(T*)(buf.ptr)) = num;
	
	return buf;
}

T value(T)(ubyte[] buf) if (isNumeric!T) {
	return (*cast(T*)(buf.ptr));
}
````

And example usage:
````
double foo = 3.14;

writeln(foo); // Prints 3.14

ubyte[] bar = foo.bytes;

writeln(bar); // Prints the bytes equal to 3.14

foo = bar.value!double;

writeln(foo); // Prints 3.14
````

On Thursday, 1 December 2016 at 07:13:45 UTC, Bauss wrote:
> On Thursday, 1 December 2016 at 00:36:30 UTC, Jake Pittis wrote:
>> [...]
>
> You could do something like below which will allow you to serialize any number.
>
> ````
> import std.stdio : writeln;
> import std.traits : isNumeric;
>
> ubyte[] bytes(T)(T num) if (isNumeric!T) {
> 	auto buf = new ubyte[T.sizeof];
> 	
> 	(*cast(T*)(buf.ptr)) = num;
> 	
> 	return buf;
> }
>
> T value(T)(ubyte[] buf) if (isNumeric!T) {
> 	return (*cast(T*)(buf.ptr));
> }
> ````
>
> And example usage:
> ````
> double foo = 3.14;
>
> writeln(foo); // Prints 3.14
>
> ubyte[] bar = foo.bytes;
>
> writeln(bar); // Prints the bytes equal to 3.14
>
> foo = bar.value!double;
>
> writeln(foo); // Prints 3.14
> ````

Regarding the test assertion that failed. Turns out I had a bug in the test. (of course)
This last solution is very pretty. Thanks.

You folks are all so kind!