better formatting

foo.ml

let rec lexwhile prop inp =
  match inp with
  | c::cs when prop c -> let tok,rest = lexwhile prop cs in c^tok,rest 
  | _ -> "",inp
;;
  
let rec lex inp =
  match snd(lexwhile space inp) with
  | [] -> [] 
  | c::cs -> 
    let prop =  
      if alphanumeric(c) then alphanumeric
      else if symbolic(c) then symbolic
      else fun c -> false 
    in
    let toktl,rest = lexwhile prop cs in
    (c^toktl)::lex rest
;;