Converting to base N

struct Number
    integer size = 0
    integer base = 0
    integer array digit [1000]
    
    method convertBase takes integer outputBase returns nothing
        local integer i = 1
        local integer n
        local integer val = 0
        local integer pow = 1
        loop
            exitwhen i > .size
                set val = val + pow*.digit[i] // try to avoid all this
                set pow = pow * .base
            set i = i + 1
        endloop
        set i = 1
        loop
            set n =  val - (val / outputBase) * outputBase
            if n < 0 then
                set n = n + outputBase
            endif
            set .digit[i] = n
            set val = val / outputBase
            exitwhen val <= 0
            set i = i + 1
        endloop
        set .size = i
        set .base = outputBase
    endmethod
    
    method setNumber takes integer val returns nothing
        local integer i = 1
        local integer n
        loop
            set n = val - (val / 10) * 10
            if n < 0 then
                set n = n + 10
            endif
            set .digit[i] = n
            set val = val / 10
            exitwhen val <= 0
            set i = i + 1
        endloop
        set .size = i
        set .base = 10
    endmethod
    
    method displayNum takes nothing returns string
        local string charMap = "0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ"
        local integer maxBase = StringLength(charMap)
        local integer i = .size
        local string s = ""
        if .base > maxBase then
            return "Base > Max Base"
        endif
        loop
            exitwhen i < 1
            set s = s+SubString(charMap, .digit[i], .digit[i]+1)
            set i = i-1
        endloop
        return s            
    endmethod
endstruct

function toStringBaseN takes integer n, integer b returns string
  local integer d
  local string s = ""
  local string chars = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ"

  //check for special cases and validate input
  if (b < 2 or b > 36) then
    return "Unsupported Base"
  elseif (n == 0) then
    return "0"
  elseif (n < 0) then
    return "-" + toStringBaseN(-n)
  endif
  
  //get digits by repeated division/remainder
  loop
    exitwhen n == 0
    set d = ModuloInteger(n, b)
    set s = SubStringBJ(chars, d, d) + s
    set n = n / b
  endloop
  return s
endfunction