# a tree-drawing grammar 
 
# interpreted as:
#
# f = draw
# + = turn-left
# - = turn-right
# [ = remember-current-position
# ] = return-to-last-position

{
<start>
  <X>
}

{
<X>
  f-[[x]+x]+f[+fx]-x
}

{
<F>
  ff
}