bignum.sh

bn_create() {
  local s="${1}"
  local sign='+'
  local lastdigit='0'
  local len=${#s}
  (( len-- ))
  declare -a digits

  local c=''
  local count=0
  local index=''

  for ((c=len; c>0; c-- ))
  do
    digits[${#digits[@]}]=${s:${c}:1}
  done

  
  if [ "${s:0:1}" == '-' ] || [ "${s:0:1}" == '+' ]
  then
    sign="${s:0:1}"
  else
    digits[${#digits[@]}]=${s:0:1}
  fi
  bn_sanitize "${sign}|${digits[*]}"
}

bn_sanitize() {
  local n="${1}"
  local nSign="$( bn_sign "${n}" )"
  local nDigits=( $( bn_digits "${n}" ) )

  while [ ${#nDigits[@]} -gt 1 ] && [ ${nDigits[$(( ${#nDigits[*]} - 1))]} -eq 0 ] 
  do
    unset nDigits[$(( ${#nDigits[*]} - 1))]
  done

  [ ${#nDigits[*]} -eq 1 ] &&
  [ "${nDigits[0]}" -eq 0 ] &&
  nSign='+'

  echo -n "${nSign}|${nDigits[*]}"
}

BignumCreationTest.sh

#!/bin/bash -

source ../bignum.sh

testBignumSanitize() {
  local a='+|4 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0'

  assertEquals "Sanitize failed." "$( bn_sanitize "${a}" )" '+|4'
}

testBignumCreation() {
  local a="$( bn_create 12345 )"
  local nega="$( bn_create -12345 )"
  local z="$( bn_create 0 )"
  local negz="$( bn_create -0 )"

  assertEquals "a != '+|5 4 3 2 1'" '+|5 4 3 2 1' "${a}"
  assertEquals "nega != '-|5 4 3 2 1'" '-|5 4 3 2 1' "${nega}"
  assertEquals "z != '+|0'" '+|0' "${z}"
  assertEquals "negz != '+|0'; 0 is always positive" '+|0' "${negz}"
}

source ./shunit2/shunit2