Pointer Arithmetic in Nim

This module implements basic pointer arithmetic and other pointer utilities for personal use.

Credit

Original library by Kaushal Modi who credited most of the code in the library to this code snippet authored by Nim Forum user Jehan.

Usage

Ops are annotated with ! to prevent unintentional use.

when isMainModule:
  import std/[strformat]

  var
    a: array[0 .. 3, int]
    p = addr(a[0])                                # p is pointing to a[0]

  for i, _ in a:
    a[i] += i
  echo &"before                    : a = {a}"

  p +!= 1                                          # p is now pointing to a[1]
  p[] = 100                                       # p[] is accessing the contents of a[1]
  echo &"after p +!= 1; p[] = 100   : a = {a}"

  p[0] = 200                                      # .. so does p[0]
  echo &"after p[0] = 200          : a = {a}"

  p[1] -= 2                                       # p[1] is accessing the contents of a[2]
  echo &"after p[1] -= 2           : a = {a}"

  p[2] += 50                                      # p[2] is accessing the contents of a[3]
  echo &"after p[2] += 50          : a = {a}"

  p +!= 2                                          # p is now pointing to a[3]
  p[-1] += 77                                     # p[-1] is accessing the contents of a[2]
  echo &"after p +!= 2; p[-1] += 77 : a = {a}"

  echo &"a[0] = p[-3] = {p[-3]}"
  echo &"a[1] = p[-2] = {p[-2]}"
  echo &"a[2] = p[-1] = {p[-1]}"
  echo &"a[3] = p[0] = {p[0]}"

  doAssert a == [0, 200, 77, 53]

Implements: +!, -!, +!=, -!=, ==!, !=!

I chose ! as the annotation arbitrarily to not interfere with % native annotation for unsigned arithmetic. In hindsight, it can visually be confusing as a not operation of sorts.

Bitops

Bitwise op arithmetic is also available as a separate import to prevent misuse:

import parith/bitops

Pointer String Formatting

String formatting for pointers is available to quickly convert pointers to string in hex ($!) or bin ($%) format

import parith/ptrformat