code for dblabeledarrow

> dblabeledarrow:=proc(tail,head,scalefactors, text,txtshift, size, colr)
local A1,A2:
A1:=labeledarrow(tail,head,scalefactors, text,txtshift, size, colr):
A2:=labeledarrow(head,tail,scalefactors, ``,txtshift, size, colr):
plots[display]([A1,A2]):
end;