create a reference to an array in Nim

Question

var b: array[5, int]

type
    ArrRef = ref array[5, int]

var c : ArrRef
echo repr(c) # nil
c = addr b # doesn't compile, says type is Array constructor, expected reference

In Nim, how can I pass references to arrays instead of passing by value? See the above code for what I have so far.

Answer 1

In Nim refs are on the heap and have to be allocated with new. You can't just use a stack array as a ref because that would be unsafe: When the array disappears from the stack, the ref points to some wrong memory. Instead you have two choices: You can use unsafe ptrs instead. Other than refs, they are not garbage collected and can be used for unsafe stuff. Alternatively you can make b a ref array directly.