(** Verifica se uma string é substring de outra.
@param stringToBeFound Cadeia de caracteres pelo qual procuramos
@param stringToBeChecked Cadeia de caracteres aonde procurar *)
and checkIfStringIsContainedIn stringToBeFound stringToBeChecked initialPos =
    if initialPos < String.length stringToBeChecked &&
       length stringToBeChecked <= length stringToBeFound then
        ( let subString = (String.sub stringToBeChecked initialPos (String.length stringToBeFound)) in
              if stringToBeFound = subString then true
              else checkIfStringIsContainedIn stringToBeFound subString (initialPos+1) )
    else false