I am trying to follow the ocaml manual to draw something. But here is a strange response from Ocaml's toplevel. Anyone sees why? Thanks.
# #load "graphics.cma";;
# Graphics.open_graph "foo:0";;
_X11TransSocketINETConnect() can't get address for foo:6000: nodename nor servname provided, or not known
Exception: Graphics.Graphic_failure "Cannot open display foo:0".