cradle.pas

{--------------------------------------------------------------}
program cradle;

{--------------------------------------------------------------}
{ Constant Declarations }

const TAB = ^I;
       CR = ^M;
       LF = ^J;

{--------------------------------------------------------------}
   { Variable Declarations }

var Look: char;       { Lookahead Character }

{--------------------------------------------------------------}
   { Read New Character From Input Stream }

procedure GetChar;
begin
   Read(Look);
end;

{--------------------------------------------------------------}
{ Report an Error }

procedure Error(s : string);
begin
   WriteLn;
   WriteLn(^G, 'Error: ', s, '.');
end;


{--------------------------------------------------------------}
{ Report Error and Halt }

procedure Abort(s : string);
begin
   Error(s);
   Halt;
end;


{--------------------------------------------------------------}
{ Report What Was Expected }

procedure Expected(s : string);
begin
   Abort(s + ' Expected');
end;


{--------------------------------------------------------------}
{ Recognize an Alpha Character }

function IsAlpha(c : char) : boolean;
begin
   IsAlpha := upcase(c) in ['A'..'Z'];
end;


{--------------------------------------------------------------}

{ Recognize a Decimal Digit }

function IsDigit(c : char) : boolean;
begin
   IsDigit := c in ['0'..'9'];
end;


{--------------------------------------------------------------}
{ Recognize an Alphanumeric }

function IsAlNum(c : char) : boolean;
begin
   IsAlNum := IsAlpha(c) or IsDigit(c);
end;


{--------------------------------------------------------------}
{ Recognize an Addop }

function IsAddop(c : char) : boolean;
begin
   IsAddop := c in ['+', '-'];
end;


{--------------------------------------------------------------}
{ Recognize a Mulop }
function IsMulop(c : char) : boolean;
begin
   IsMulop := c in ['*', '/'];
end;


{--------------------------------------------------------------}
{ Recognize White Space }

function IsWhite(c : char) : boolean;
begin
   IsWhite := c in [' ', TAB];
end;


{--------------------------------------------------------------}
{ Skip Over Leading White Space }

procedure SkipWhite;
begin
   while IsWhite(Look) do
      GetChar;
end;


{--------------------------------------------------------------}
{ Match a Specific Input Character }

procedure Match(x : char);
begin
   if Look <> x then Expected('''' + x + '''');
   GetChar;
   SkipWhite;
end;


{--------------------------------------------------------------}
{ Skip a CRLF }

procedure Fin;
begin
   if Look = CR then GetChar;
   if Look = LF then GetChar;
   SkipWhite;
end;


{--------------------------------------------------------------}
{ Get an Identifier }

function GetName : char;
begin
   if not IsAlpha(Look) then Expected('Name');
   GetName := UpCase(Look);
   GetChar;
end;


{--------------------------------------------------------------}
{ Get a Number }

function GetNum : char;
begin
   if not IsDigit(Look) then Expected('Integer');
   GetNum := Look;
   GetChar;
end;


{--------------------------------------------------------------}
{ Output a String with Tab }

procedure Emit(s : string);
begin
   Write(TAB, s);
end;


{--------------------------------------------------------------}
{ Output a String with Tab and CRLF }

procedure EmitLn(s : string);
begin
   Emit(s);
   WriteLn;
end;


{--------------------------------------------------------------}
{ Initialize }

procedure Init;
begin
   GetChar;
end;


{--------------------------------------------------------------}
{ Main Program }

begin
   Init;
end.
{--------------------------------------------------------------}