the new decomposition method of adding - 3rd grade

addition_decomp.nim

import os, strutils, math

if paramCount() < 2:
  echo "Error: supply two integers"
  quit(QuitFailure)

var a, b: int
var hundreds, tens, ones: int

try:
  a = parseInt(paramStr(1))
  b = parseInt(paramStr(2))
except ValueError:
  echo "Error: one of those was not an integer"
  quit(QuitFailure)

let answer = a+b
echo "Problem: ", a, " plus ", b, " equals ", answer

echo "Decompose with math:"
hundreds = (a div 100 * 100)
a -= hundreds
tens = (a div 10 * 10)
a -= tens
ones = a
echo hundreds, "+", tens, "+", ones

echo "Decompose with strings:"
proc get_place(s:string, place:int, mult:int): int=
  let digit:char = s[s.len - place]
  return parseInt( $digit ) * mult

let x = paramStr(1)
let y = paramStr(2)

hundreds = get_place(x, 3, 100) + get_place(y, 3, 100)
tens = get_place(x, 2, 10) + get_place(y, 2, 10)
ones = get_place(x, 1, 1) + get_place(y, 1, 1)

let answer2 = hundreds+tens+ones

if answer != answer2:
  echo "Error: answers not equal!"

echo hundreds, " + ", tens, " + ", ones, " = ", (hundreds+tens+ones)