This is really a particluar need, Can it be done otherwise, i.e. reject the
proposed solution and look again to the problem, because, although it was done,
it does not make such sens for the "Why?" question.
the reason I thought this way, was because I translated the Nim code in my head
to C, to something like that:
void flt2arr(double x, uint8_t[] result) {
for(int i = 0; i < 8; i++)
result[i] = (uint8_t*) + i;
}
Run
But as @araq said, this is not what
Does it also use an union when compiling to C++?
In C99 (ISO/IEC 9899:1999 6.5/7; the exact same wording is used in ISO/IEC
9899:2011 ยง6.5/7)
> An object shall have its stored value accessed only by an lvalue expression
> that has one of the following types ... a character type.
The meaning of "a character type" here includes unsigned char,
The following should also be safe, this translates to a memcpy() at the C
level. This may seem like overkill, but the C compiler should recognize the use
of memcpy for type punning and optimize it away and generate a register to
register move.
proc flt2arr(f: var float64, a: var
afaik atleast in C there's no "safe" way to do it. The method presented by @e
works in most situations, but breaks strict aliasing (a poiner of one type may
not be casted to a pointer of an incompatible type).
The usual safer way, in C is by using a union:
type
Thank you very much, this is exactly what I need. I was thinking about using
casts but wasn't really sure if it's safe.
Here's a little program demonstrating conversion functions:
import parseutils, os
func flt2arr (x: float64) : array[0..7, uint8] =
result = cast[array[0..7, uint8]](x)
func arr2flt (a: array[0..7, uint8]) : float64 =
result = cast[float64](a)
