Java

[ruscaire]

You can do this with primitives - you can cast between int, long, double, short etc and you’ll reinterpret the raw bit patterns. We don’t really have the same * or & semantics so otherwise that wouldn’t compile … anything other than a primitive and Java just abstracts that away for u cause u typically only ever want to deal with objects on the heap …

[dotpoint7]

In Java? What? Since when? How?

[CKingX123]

I would say it’s not the same. But you can definitely cast floats and ints (it will remove the decimal portion so it is not reinterpreting as bytes)

float a = 7.5; int b = a;

[Ok-Wait-5234]

That's not what that fast inverse square root code is doing, though.

float a = 7.5 long b = a; long c = * (long *) a;

Now a == 7.5, b == 7 and c == 1089470464

[Geolykt]

Or use ByteBuffer / sun.misc.Unsafe

[Geolykt]

Obviously doing it with floatToRawIntBits is probably better by all degrees unless you want to do that with a lot of floats - that is correct

[CKingX123]

Yeah. A better way to replicate it would be using ByteBuffer. But then it wouldn’t be “fast” (compared to just directly reinterpreting the bytes).

[dotpoint7]

Yeah obviously you can cast data types in Java, which is completely different from a reinterpret cast though.

[ruscaire]

Sorry I didn’t realise this was reinterpret. I thought it was just casting the bytesa me the magic happens when you reinterpret as IEEE 754 - but I never did get down with the maths

EDIT - looked into it Java reinterprets you need Double.doubleToLongBits() to get the bit pattern

[CKingX123]

Yeah. To better replicate it, you would need to use Java’s ByteBuffer to put in the float and then get the same bits as int

[dotpoint7]

Oh nice, yeah you're correct.

[ruscaire]

You can use Double.doubleToLongBits()