PL0-GNU-M2/New-PL0/PL0c1.mod

MODULE PL0c1;
(************************************************************)
(* PL0 compiler in GNU Modula-2                             *)
(*    using only ISO Libraries to void mixing               *)
(* generates an asm file to be interpreted by PLO executable*)
(* Eric Streit <eric@yojik.eu>  May 2026                    *)
(************************************************************)

(* program structure                             *)
(* read a file with the text program             *)
(* syntax analysis followed by semantic analysis *)
(* and code generation                           *)

FROM IOResult   IMPORT ReadResults, ReadResult; 
FROM TextIO     IMPORT ReadRestLine, SkipLine, ReadToken, WriteLn, WriteString, ReadChar;
FROM SeqFile IMPORT OpenRead, OpenWrite, OpenResults, Close, ChanId, read, write;
IMPORT STextIO, SWholeIO;

VAR 
    theChanId       : ChanId;
    theResult       : OpenResults; 
    theChar         : CHAR;
    theLineNumber   : CARDINAL;


BEGIN
    STextIO.WriteString("PL0 compiler from Wirth book 'Algorithms and Data Structures'");
    STextIO.WriteLn;
    STextIO.WriteString("Eric Streit <eric@yojik.eu>");
    STextIO.WriteLn;
    STextIO.WriteLn;

    theLineNumber := 1;
    OpenRead(theChanId, "test1.pl0", read, theResult);
    IF theResult = noSuchFile THEN
        STextIO.WriteString("Sorry, this file doesn't exist ; halting");
        STextIO.WriteLn;
    ELSE
        IF theResult=opened THEN 
            (* file is open*)
            STextIO.WriteString("file opened!");
            STextIO.WriteLn;
            STextIO.WriteLn;
            (* reading a char*)
            ReadChar(theChanId, theChar);
            (* testing the result *)
            (* if OK we continue *)
            WHILE ReadResult(theChanId) <> endOfInput DO 
                (* testing end of line *)
                IF ReadResult(theChanId) = endOfLine THEN
                    INC(theLineNumber);
                    (* we have to 'skip' the endOfLine ... so strange *)
                    SkipLine(theChanId);
                END;
                (* printing the char*)
                STextIO.WriteChar(theChar);
                (* reading next char *)
                ReadChar(theChanId, theChar);
            END;
            Close(theChanId);
        ELSE
            STextIO.WriteString("Error");
            STextIO.WriteLn;
        END;
    END;
    

END PL0c1.