Appendix D: Specification of the Package Ada.Text_IO

This appendix, adapted from the Ada 95 Reference Manual, Section A.10.1, gives the specification for Ada.Text_IO. Note that the numeric sub-packages Integer_IO and Float_IO are given here as generic. The standard also provides for the preinstantiated packages Ada.Integer_Text_IO and Ada.Float_Text_IO as we have used in this book. These last two packages are part of the standard libraries and do not need to be created or compiled by the user.
Explanations of the most common input/output exceptions are given in Appendix H, along with the other exceptions likely to be encountered by a student.
WITH Ada.IO_Exceptions;
PACKAGE Ada.Text_IO IS

  TYPE File_Type IS limited private;

  TYPE File_Mode IS ( In_File, Out_File, Append_File);

  TYPE Count IS RANGE  0.. implementation-defined;
  SUBTYPE Positive_Count IS Count RANGE  1 .. Count'Last;
  Unbounded : CONSTANT Count :=  ; -- line and page length

  SUBTYPE Field       IS Integer RANGE  0 .. implementation-defined;
  SUBTYPE Number_Base IS Integer RANGE  2 .. 16;

  TYPE Type_Set IS ( Lower_Case, Upper_Case);

  -- File Management

  PROCEDURE Create ( File : IN out File_Type;
                     Mode : IN File_Mode := Out_File;
                     Name : IN String    := "";
                     Form : IN String    := "");

  PROCEDURE Open   ( File : IN out File_Type;
                     Mode : IN File_Mode;
                     Name : IN String;
                     Form : IN String := "");

  PROCEDURE Close  ( File : IN out File_Type);
  PROCEDURE Delete ( File : IN out File_Type);
  PROCEDURE Reset  ( File : IN out File_Type; Mode : IN File_Mode);
  PROCEDURE Reset  ( File : IN out File_Type);

  FUNCTION  Mode   ( File : IN File_Type) RETURN File_Mode;
  FUNCTION  Name   ( File : IN File_Type) RETURN String;
  FUNCTION  Form   ( File : IN File_Type) RETURN String;

  FUNCTION  Is_Open( File : IN File_Type) RETURN Boolean;

  -- Control of default input and output files

  PROCEDURE Set_Input ( File : IN File_Type);
  PROCEDURE Set_Output( File : IN File_Type);
  PROCEDURE Set_Error ( File : IN File_Type);

  FUNCTION Standard_Input  RETURN File_Type;
  FUNCTION Standard_Output RETURN File_Type;
  FUNCTION Standard_Error  RETURN File_Type;

  FUNCTION Current_Input   RETURN File_Type;
  FUNCTION Current_Output  RETURN File_Type;
  FUNCTION Current_Error   RETURN File_Type;

  TYPE File_Access IS ACCESS CONSTANT File_Type;

  FUNCTION Standard_Input  RETURN File_Access;
  FUNCTION Standard_Output RETURN File_Access;
  FUNCTION Standard_Error  RETURN File_Access;

  FUNCTION Current_Input   RETURN File_Access;
  FUNCTION Current_Output  RETURN File_Access;
  FUNCTION Current_Error   RETURN File_Access;

    --Buffer control
  PROCEDURE Flush ( File : IN OUT File_Type);
  PROCEDURE Flush;

  -- Specification of line and page lengths

  PROCEDURE Set_Line_Length( File : IN File_Type; To : IN Count);
  PROCEDURE Set_Line_Length( To   : IN Count);

  PROCEDURE Set_Page_Length( File : IN File_Type; To : IN Count);
  PROCEDURE Set_Page_Length( To   : IN Count);

  FUNCTION  Line_Length( File : IN File_Type) RETURN Count;
  FUNCTION  Line_Length RETURN Count;

  FUNCTION  Page_Length( File : IN File_Type) RETURN Count;
  FUNCTION  Page_Length RETURN Count;

  -- Column, Line, and Page Control

  PROCEDURE New_Line   ( File    : IN File_Type;
                         Spacing : IN Positive_Count :=  );
  PROCEDURE New_Line   ( Spacing : IN Positive_Count :=  );

  PROCEDURE Skip_Line  ( File    : IN File_Type;
                         Spacing : IN Positive_Count :=  );
  PROCEDURE Skip_Line  ( Spacing : IN Positive_Count :=  );

  FUNCTION  End_Of_Line( File : IN File_Type) RETURN Boolean;
  FUNCTION  End_Of_Line RETURN Boolean;

  PROCEDURE New_Page   ( File : IN File_Type);
  PROCEDURE New_Page;

  PROCEDURE Skip_Page  ( File : IN File_Type);
  PROCEDURE Skip_Page;

  FUNCTION  End_Of_Page( File : IN File_Type) RETURN Boolean;
  FUNCTION  End_Of_Page RETURN Boolean;

  FUNCTION  End_Of_File( File : IN File_Type) RETURN Boolean;
  FUNCTION  End_Of_File RETURN Boolean;

  PROCEDURE Set_Col ( File : IN File_Type; To : IN Positive_Count);
  PROCEDURE Set_Col ( To   : IN Positive_Count);

  PROCEDURE Set_Line( File : IN File_Type; To : IN Positive_Count);
  PROCEDURE Set_Line( To   : IN Positive_Count);

  FUNCTION Col ( File : IN File_Type) RETURN Positive_Count;
  FUNCTION Col  RETURN Positive_Count;

  FUNCTION Line( File : IN File_Type) RETURN Positive_Count;
  FUNCTION Line RETURN Positive_Count;

  FUNCTION Page( File : IN File_Type) RETURN Positive_Count;
  FUNCTION Page RETURN Positive_Count;

  -- Character Input-Output

  PROCEDURE Get( File : IN  File_Type; Item : OUT Character);
  PROCEDURE Get( Item : OUT Character);

  PROCEDURE Put( File : IN  File_Type; Item : IN Character);
  PROCEDURE Put( Item : IN  Character);

  PROCEDURE Look_Ahead ( File        : IN  File_Type;
                         Item        : OUTCharacter;
                         End_Of_Line : OUT Boolean);
  PROCEDURE Look_Ahead ( Item        : OUT Character;
                         End_Of_Line : OUT Boolean);

  PROCEDURE Get_Immediate( File      : IN  File_Type;
                           Item      : OUT Character);
  PROCEDURE Get_Immediate( Item      : OUT Character);

  PROCEDURE Get_Immediate( File      : IN  File_Type;
                           Item      : OUT Character;
                           Available : OUT Boolean);
  PROCEDURE Get_Immediate( Item      : OUT Character;
                           Available : OUT Boolean);

  -- String Input-Output

  PROCEDURE Get( File : IN  File_Type; Item : OUT String);
  PROCEDURE Get( Item : OUT String);

  PROCEDURE Put( File : IN  File_Type; Item : IN String);
  PROCEDURE Put( Item : IN  String);

  PROCEDURE Get_Line( File : IN  File_Type;
                      Item : OUT String;
                      Last : OUT Natural);
  PROCEDURE Get_Line( Item : OUT String; Last : OUT Natural);

  PROCEDURE Put_Line( File : IN  File_Type; Item : IN String);
  PROCEDURE Put_Line( Item : IN  String);

    -- Generic packages for Input-Output of Integer Types

  GENERIC
     TYPE Num IS RANGE <>;
  PACKAGE Integer_IO IS

     Default_Width : Field := Num'Width;
     Default_Base  : Number_Base := 10;

     PROCEDURE Get( File  : IN  File_Type;
                    Item  : OUT Num;
                    Width : IN Field := 0);
     PROCEDURE Get( Item  : OUT Num;
                    Width : IN  Field := 0);

     PROCEDURE Put( File  : IN File_Type;
                    Item  : IN Num;
                    Width : IN Field := Default_Width;
                    Base  : IN Number_Base := Default_Base);
     PROCEDURE Put( Item  : IN Num;
                    Width : IN Field := Default_Width;
                    Base  : IN Number_Base := Default_Base);
     PROCEDURE Get( From : IN  String;
                    Item : OUT Num;
                    Last : OUT Positive);
     PROCEDURE Put( To   : OUT String;
                    Item : IN Num;
                    Base : IN Number_Base := Default_Base);

  END Integer_IO;

  GENERIC
     TYPE Num IS mod <>;
  PACKAGE Modular_IO IS

     Default_Width : Field := Num'Width;
     Default_Base  : Number_Base :=   ;

     PROCEDURE Get( File  : IN  File_Type;
                    Item  : OUT Num;
                    Width : IN Field := 0);
     PROCEDURE Get( Item  : OUT Num;
                    Width : IN  Field := 0);

     PROCEDURE Put( File  : IN File_Type;
                    Item  : IN Num;
                    Width : IN Field := Default_Width;
                    Base  : IN Number_Base := Default_Base);
     PROCEDURE Put( Item  : IN Num;
                    Width : IN Field := Default_Width;
                    Base  : IN Number_Base := Default_Base);
     PROCEDURE Get( From : IN  String;
                    Item : OUT Num;
                    Last : OUT Positive);
     PROCEDURE Put( To   : OUT String;
                    Item : IN Num;
                    Base : IN Number_Base := Default_Base);

  END Modular_IO;
  -- Generic PACKAGEs for Input-Output of Real Types

  GENERIC
     TYPE Num IS digits <>;
  PACKAGE Float_IO IS

     Default_Fore : Field := 2;
     Default_Aft  : Field := Num'Digits-1 ;
     Default_Exp  : Field := 3;

     PROCEDURE Get( File  : IN  File_Type;
                   Item  : OUT Num;
                    Width : IN  Field := 0);
     PROCEDURE Get( Item  : OUT Num;
                    Width : IN  Field := 0);

     PROCEDURE Put( File : IN File_Type;
                    Item : IN Num;
                    Fore : IN Field := Default_Fore;
                    Aft  : IN Field := Default_Aft;
                    Exp  : IN Field := Default_Exp);
     PROCEDURE Put( Item : IN Num;
                    Fore : IN Field := Default_Fore;
                    Aft  : IN Field := Default_Aft;
                    Exp  : IN Field := Default_Exp);

     PROCEDURE Get( From : IN String;
                    Item : OUT Num;
                    Last : OUT Positive);
     PROCEDURE Put( To   : OUT String;
                    Item : IN Num;
                    Aft  : IN Field := Default_Aft;
                    Exp  : IN Field := Default_Exp);
  END Float_IO;

  GENERIC
     TYPE Num IS delta <>;
  PACKAGE Fixed_IO IS

     Default_Fore : Field := Num'Fore;
     Default_Aft  : Field := Num'Aft;
     Default_Exp  : Field := 0;

     PROCEDURE Get( File  : IN  File_Type;
                    Item  : OUT Num;
                    Width : IN  Field := 0);
     PROCEDURE Get( Item  : OUT Num;
                    Width : IN  Field := 0);

     PROCEDURE Put( File : IN File_Type;
                    Item : IN Num;
                    Fore : IN Field := Default_Fore;
                    Aft  : IN Field := Default_Aft;
                    Exp  : IN Field := Default_Exp);
     PROCEDURE Put( Item : IN Num;
                    Fore : IN Field := Default_Fore;
                    Aft  : IN Field := Default_Aft;
                    Exp  : IN Field := Default_Exp);

     PROCEDURE Get( From : IN  String;
                    Item : OUT Num;
                    Last : OUT Positive);
     PROCEDURE Put( To   : OUT String;
                    Item : IN Num;
                    Aft  : IN Field := Default_Aft;
                    Exp  : IN Field := Default_Exp);
  END Fixed_IO;

  GENERIC
     TYPE Num IS DELTA <> DIGITS <>;
  PACKAGE Decimal_IO IS

     Default_Fore : Field := Num'Fore;
     Default_Aft  : Field := Num'Aft;
     Default_Exp  : Field := 0;

     PROCEDURE Get( File  : IN  File_Type;
                    Item  : OUT Num;
                    Width : IN  Field := 0);
     PROCEDURE Get( Item  : OUT Num;
                    Width : IN  Field := 0);

     PROCEDURE Put( File : IN File_Type;
                    Item : IN Num;
                    Fore : IN Field := Default_Fore;
                    Aft  : IN Field := Default_Aft;
                    Exp  : IN Field := Default_Exp);
     PROCEDURE Put( Item : IN Num;
                    Fore : IN Field := Default_Fore;
                    Aft  : IN Field := Default_Aft;
                    Exp  : IN Field := Default_Exp);

     PROCEDURE Get( From : IN  String;
                    Item : OUT Num;
                    Last : OUT Positive);
     PROCEDURE Put( To   : OUT String;
                    Item : IN Num;
                    Aft  : IN Field := Default_Aft;
                    Exp  : IN Field := Default_Exp);
  END Decimal_IO;

  -- Generic package for Input-Output of Enumeration Types

  GENERIC
     TYPE Enum IS ( <>);
  PACKAGE Enumeration_IO IS

     Default_Width   : Field := 0;
     Default_Setting : Type_Set := Upper_Case;

     PROCEDURE Get( File : IN  File_Type;
                    Item : OUT Enum);
     PROCEDURE Get( Item : OUT Enum);

     PROCEDURE Put( File  : IN File_Type;
                    Item  : IN Enum;
                    Width : IN Field    := Default_Width;
                    Set   : IN Type_Set := Default_Setting);
     PROCEDURE Put( Item  : IN Enum;
                    Width : IN Field    := Default_Width;
                    Set   : IN Type_Set := Default_Setting);

     PROCEDURE Get( From : IN  String;
                    Item : OUT Enum;
                    Last : OUT Positive);
     PROCEDURE Put( To   : OUT String;
                    Item : IN  Enum;
                    Set  : IN  Type_Set := Default_Setting);
  END Enumeration_IO;

    -- Exceptions

  Status_Error : EXCEPTION RENAMES IO_Exceptions.Status_Error;
  Mode_Error   : EXCEPTION RENAMES IO_Exceptions.Mode_Error;
  Name_Error   : EXCEPTION RENAMES IO_Exceptions.Name_Error;
  Use_Error    : EXCEPTION RENAMES IO_Exceptions.Use_Error;
  Device_Error : EXCEPTION RENAMES IO_Exceptions.Device_Error;
  End_Error    : EXCEPTION RENAMES IO_Exceptions.End_Error;
  Data_Error   : EXCEPTION RENAMES IO_Exceptions.Data_Error;
  Layout_Error : EXCEPTION RENAMES IO_Exceptions.Layout_Error;

PRIVATE
  ... -- not specified by the language
END Ada.Text_IO;