Task: Rot-13


C++: #include <iostream>
#include <istream>
#include <ostream>
#include <fstream>
#include <cstdlib>
#include <string>


std::string rot13(std::string s)
{
  static std::string const
    lcalph = "abcdefghijklmnopqrstuvwxyz",
    ucalph = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";

  std::string result;
  std::string::size_type pos;

  result.reserve(s.length());

  for (std::string::iterator it = s.begin(); it != s.end(); ++it)
  {
    if ( (pos = lcalph.find(*it)) != std::string::npos )
      result.push_back(lcalph[(pos+13) % 26]);
    else if ( (pos = ucalph.find(*it)) != std::string::npos )
      result.push_back(ucalph[(pos+13) % 26]);
    else
      result.push_back(*it);
  }

  return result;
}




int rot13_stream(std::istream& is)
{
  std::string line;
  while (std::getline(is, line))
  {
    if (!(std::cout << rot13(line) << "\n"))
      return false;
  }
  return is.eof();
}


int main(int argc, char* argv[])
{
  if (argc == 1) 
    return rot13_stream(std::cin)? EXIT_SUCCESS : EXIT_FAILURE;

  std::ifstream file;
  for (int i = 1; i < argc; ++i)
  {
    file.open(argv[i], std::ios::in);
    if (!file)
    {
      std::cerr << argv[0] << ": could not open for reading: " << argv[i] << "\n";
      return EXIT_FAILURE;
    }
    if (!rot13_stream(file))
    {
      if (file.eof())
        
        std::cerr << argv[0] << ": error writing to stdout\n";
      else
        std::cerr << argv[0] << ": error reading from " << argv[i] << "\n";
      return EXIT_FAILURE;
    }
    file.clear();
    file.close();
    if (!file)
      std::cerr << argv[0] << ": warning: closing failed for " << argv[i] << "\n";
  }
  return EXIT_SUCCESS;
}










Ada: with Ada.Text_IO.Text_Streams; use Ada.Text_IO.Text_Streams;
with Ada.Strings.Maps; use Ada.Strings.Maps;
with Ada.Command_Line; use Ada.Command_Line;

procedure Rot_13 is
   
   From_Sequence : Character_Sequence := "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ";
   Result_Sequence : Character_Sequence := "nopqrstuvwxyzabcdefghijklmNOPQRSTUVWXYZABCDEFGHIJKLM";
   Rot_13_Mapping : Character_Mapping := To_Mapping(From_Sequence, Result_Sequence);

   In_Char : Character;
   Stdio : Stream_Access := Stream(Ada.Text_IO.Standard_Input);
   Stdout : Stream_Access := Stream(Ada.Text_Io.Standard_Output);
   Input : Ada.Text_Io.File_Type;
 
begin
   if Argument_Count > 0 then
      for I in 1..Argument_Count loop
         begin
            Ada.Text_Io.Open(File => Input, Mode => Ada.Text_Io.In_File, Name => Argument(I));
            Stdio := Stream(Input);
             while not Ada.Text_Io.End_Of_File(Input) loop
               In_Char :=Character'Input(Stdio); 
               Character'Output(Stdout, Value(Rot_13_Mapping, In_Char));
            end loop;
            Ada.Text_IO.Close(Input);
         exception
            when Ada.Text_IO.Name_Error =>
               Ada.Text_Io.Put_Line(File => Ada.Text_Io.Standard_Error, Item => "File " & Argument(I) & " is not a file.");
            when Ada.Text_Io.Status_Error =>
               Ada.Text_Io.Put_Line(File => Ada.Text_Io.Standard_Error, Item => "File " & Argument(I) & " is already opened.");
         end;
      end loop;
   else
      while not Ada.Text_Io.End_Of_File loop
         In_Char :=Character'Input(Stdio); 
         Character'Output(Stdout, Value(Rot_13_Mapping, In_Char));
      end loop;
   end if;
end Rot_13;