libm3/src/rw/IO.i3

 Copyright 1993 by Digital Equipment Corp.                   
 All rights reserved.                                        
 See the file COPYRIGHT for a full description.              
 Last modified on Thu Sep 23 12:17:09 PDT 1993 by mcjones    
      modified on Fri Jun 18 13:27:27 PDT 1993 by wobber     
      modified on Sat Jan 26 14:38:00 PST 1993 by gnelson    


 The IO interface provides textual input and output for simple
   programs.  For more detailed control, use the interfaces Rd,
   Wr, Stdio, FileRd, FileWr, Fmt, and Lex.


   The input procedures take arguments of type Rd.T that specify
   which input stream to use.  If this argument is defaulted, standard
   input (Stdio.stdin) is used.  Similarly, if an argument of type
   Wr.T to an output procedure is defaulted, Stdio.stdout is used.
   


INTERFACE IO;

IMPORT Rd, Wr;

PROCEDURE Put(txt: TEXT; wr: Wr.T := NIL);

 Output txt to wr and flush wr. 

PROCEDURE PutChar(ch: CHAR; wr: Wr.T := NIL);

 Output ch to wr and flush wr. 

PROCEDURE PutWideChar(ch: WIDECHAR; wr: Wr.T := NIL);

 Output ch to wr and flush wr. 

PROCEDURE PutInt(n: INTEGER; wr: Wr.T := NIL);

 Output Fmt.Int(n) to wr and flush wr. 

PROCEDURE PutLongInt(n: LONGINT; wr: Wr.T := NIL);

 Output Fmt.LongInt(n) to wr and flush wr. 

PROCEDURE PutReal(r: REAL; wr: Wr.T := NIL);

 Output Fmt.Real(r) to wr and flush wr. 

PROCEDURE EOF(rd: Rd.T := NIL): BOOLEAN;

 Return TRUE iff rd is at end-of-file. 

EXCEPTION Error;

 The exception Error is raised whenever a Get procedure
   encounters syntactically invalid input, including unexpected
   end-of-file. 


PROCEDURE GetLine(rd: Rd.T := NIL): TEXT RAISES {Error};

 Read a line of text from rd and return it. 
 A line of text is either zero or more characters terminated by a
   line break, or one or more characters terminated by an end-of-file.
   In the former case, GetLine consumes the line break but does not
   include it in the returned value.  A line break is either {\tt
   "\n"} or {\tt
   "\r\n"}. 


PROCEDURE GetChar(rd: Rd.T := NIL): CHAR RAISES {Error};

 Read the next character from rd and return it. 

PROCEDURE GetWideChar(rd: Rd.T := NIL): WIDECHAR RAISES {Error};

 Read the next two bytes from rd and return it as a wide character. 

PROCEDURE GetInt(rd: Rd.T := NIL): INTEGER RAISES {Error};

 Read a decimal numeral from rd using Lex.Int and return its
   value. 

PROCEDURE GetLongInt(rd: Rd.T := NIL): LONGINT RAISES {Error};

 Read a decimal numeral from rd using Lex.LongInt and return its
   value. 

PROCEDURE GetReal(rd: Rd.T := NIL): REAL RAISES {Error};

 Read a real number from rd using Lex.Real and return its value.
   

PROCEDURE OpenRead(f: TEXT): Rd.T;

 Open the file name f for reading and return a reader on its
   contents. If the file doesn't exist or is not readable, return
   NIL. 

PROCEDURE OpenWrite(f: TEXT): Wr.T;

 Open the file named f for writing and return a writer on its
   contents.  If the file does not exist it will be created.  If the
   process does not have the authority to modify or create the file,
   return NIL. 

END IO.