function addingmachine,double=double

;+
;
; ADDINGMACHINE
; A command-line function that acts as a simple adding machine by
; taking a sequence of single numbers from user input and adding them
; together, printing a running total.
;
; Syntax:
; Result = ADDINGMACHINE([/DOUBLE])
; 
; Keyword:
; DOUBLE - Set to require double precision.
;
; Katie Peek / November 2007
; Future work: Add a /printreceipt keyword to keep track of history?
;
;-

print,' Enter values to add to displayed total.  Exit by entering "x"'

if keyword_set(double) then sum=0.0d else sum=0.0
a='0'
while (a ne 'x') do begin
  if keyword_set(double) then aa = double(a) else aa=float(a)
  sum = sum + aa
  read,a,prompt=' '+str(sum)+' + '
endwhile

return, sum
end