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Nim pointer arithmetic
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# from https://forum.nim-lang.org/t/1188#7366 by Jehan | |
# most of the time only the dereference operator is needed, import it like this: | |
# from ptrmath import `[]` | |
template `+`*[T](p: ptr T, off: int): ptr T = | |
cast[ptr type(p[])](cast[ByteAddress](p) +% off * sizeof(p[])) | |
template `+=`*[T](p: ptr T, off: int) = | |
p = p + off | |
template `-`*[T](p: ptr T, off: int): ptr T = | |
cast[ptr type(p[])](cast[ByteAddress](p) -% off * sizeof(p[])) | |
template `-=`*[T](p: ptr T, off: int) = | |
p = p - off | |
template `[]`*[T](p: ptr T, off: int): T = | |
(p + off)[] | |
template `[]=`*[T](p: ptr T, off: int, val: T) = | |
(p + off)[] = val | |
when isMainModule: | |
var a: array[0..3, int] | |
for i in a.low..a.high: | |
a[i] += i | |
var p = addr(a[0]) | |
p += 1 | |
p[0] -= 2 | |
echo p[0], " ", p[1] |
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