procedure main()
s := "-6,-3--1,3-5,7-11,14,15,17-20"
write("Input string      := ",s)
write("Expanded list   := ", list2string(range_expand(s)) | "FAILED")
end

procedure range_expand(s)          #: return list of integers extracted from an ordered string representation
local R,low,high
R := []

s ? until pos(0) do {
   put(R,low := integer(tab(upto(',-')|0))| fail)           # get lower bound
   if ="-" || (high := integer(tab(find(",")|0))|fail) then
      until low = high do put(R,low +:= 1)                  # find range
   =","
   }
return R
end

procedure list2string(L)        #: helper function to convert a list to a string
local s

   every (s := "[ ") ||:= !L || " "
   return s || "]"
end