;HW6: Simple Calculator
pro click,ev
COMMON calc,x,op
widget_control,ev.id,get_uvalue=uval
widget_control,ev.top,get_uvalue=number
widget_control,number,get_value=num
if uval eq 'plus' then begin
  dooper,x,op,num
  op='+'
  widget_control,number,set_value=''
endif
if uval eq 'minus' then begin
  dooper,x,op,num
  op='-'
  widget_control,number,set_value=''
endif
if uval eq 'equals' then begin
  dooper,x,op,num
  widget_control,number,set_value=strcompress(x,/remove_all)
  x=0.
  op=''
endif
end

pro dooper,x,op,num
   if op eq '' then x=num+0.0
   if op eq '+' then x=x+num
   if op eq '-' then x=x-num
end

COMMON calc,x,op
x=0.
op=''
calcbase=widget_base(xsize=100,ysize=60,title='Calculator')
number=widget_text(calcbase,xsize=12,/editable,/all_events,uvalue='number')
plus=widget_button(calcbase,value=' + ',yoffset=30,uvalue='plus')
minus=widget_button(calcbase,value=' - ',yoffset=30,xoffset=30,uvalue='minus')
equals=widget_button(calcbase,value=' = ',yoffset=30,xoffset=60,uvalue='equals')
widget_control,calcbase,set_uvalue=number
widget_control,calcbase,/realize
xmanager,'Calculator',calcbase,event_handler='click'
end