BSD 4_3 development

[unix-history] / usr / contrib / icon / port / meander.icn

#
#          M E A N D E R I N G   S T R I N G S
#

#  This main procedure accepts specifications for meandering strings
#  from standard input with the alphabet separated from the length by
#  a colon.

procedure main()
  local line, alpha, n
  while line := read() do {
     line ? if alpha := tab(upto(':')) then {
        move(1)
        if n := integer(tab(0)) then write(meander(alpha,n))
        else write("erroneous input")
        }
        else write("erroneous input")
     }
end

procedure meander(alpha,n)
  local result, t, i, c, k
  i := k := *alpha
  t := n-1
  result := repl(alpha[1],t)
  while c := alpha[i] do {
     if find(result[-t:0] || c,result)
     then i -:= 1
     else {result ||:= c; i := k}
     }
  return result
end