title: Have a problem summing numbers in Rexx (Creating Luhn Algorithm)
body: <p>Hello I am new to Rexx and working on creating the luhn algorithm in a subroutine get an the error when trying to add the digit to the variable to hold the sum in each iteration of my loop. The code runs with no error when I remove 'sumOfNum = sumOfNum + numToSum' statement.</p>
  <p>inspecting 7459274623941467
  108 +++        sumOfNum = sumOfNum + numToSum
  41 +++      call INSPECT
  IRX0041I Error running CCVIEW, line 108: Bad arithmetic conversion
  READY</p>
  <pre><code>INSPECT:
    say 'inspecting' cc_digits
    up = 1
    flag = 0  /* for every other digit */
  
    /* Loop to assess each digit in cc_digits */
    do i = 0 to 16 by 1
  
      /* Identify Numbers to sum */
      digit = SUBSTR(cc_digits,up,1) /* Returns digit */
      up = up + 1                    /* for next digit */
  
      /* to use only every other number */
      if (if flag = 0) then 
        do
          numToSum = 0          
          numToSum = digit * 2
          flag = 1
        end
  
      /* Skip this digit */
      else
        do
          Flag = 0
        end
  
      /*if digit &gt; 9 sum digits of digit */
      if (numToSum &gt; 9) then
        do
          digit1 = SUBSTR(cc_digits,1,1)
          digit2 = SUBSTR(cc_digits,2,1)
          numToSum = digit1 + digit2          
        end
  
      /* to accumulate sum */
      sumOfNum = sumOfNum + numToSum
    end
  RETURN
  </code></pre>