{ Report What Was Expected } procedure Expected(s: string); begin

Abort(s + Expected); end;

{ Report an Undefined Identifier } procedure Undefined(n: string); begin

Abort(Undefined Identifier + n); 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 Character } 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 a Boolean Orop } function IsOrop(c: char): boolean; begin

IsOrop := c in [j, -]; end;

{ Recognize a Relop }

function IsRelop(c: char): boolean;

begin

IsRelop := 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;

{ Skip Over an End-of-Line }

procedure NewLine;

begin

while Look = CR do begin GetChar;

if Look = LF then GetChar; SkipWhite; end; end;

{ Match a Specific Input Character }

procedure Match(x: char);

begin

NewLine;

if Look = x then GetChar

else Expected( + x + );

SkipWhite; end;

{ Table Lookup }

function Lookup(T: TabPtr; s: string; n: integer): integer; var i: integer;

found: Boolean; begin

found := false;

i := n;

while (i > 0) and not found do if s = T*[i] then

found := true else

dec(i); Lookup := i; end;

{ Locate a Symbol in Table }

{ Returns the index of the entry. Zero if not present. }

function Locate(N: Symbol): integer;

begin

Locate := Lookup(®ST, n, MaxEntry); end;

{ Look for Symbol in Table } function InTable(n: Symbol): Boolean; begin

InTable := Lookup(®ST, n, MaxEntry) <> 0; end;

{ Add a New Entry to Symbol Table } procedure AddEntry(N: Symbol; T: char); begin

if InTable(N) then Abort(Duplicate Identifier + N); if NEntry = MaxEntry then Abort(Symbol Table Full);

Inc(NEntry); ST[NEntry] := N; SType[NEntry] := T; end;

{ Get an Identifier } procedure GetName; begin

NewLine;

if not IsAlpha(Look) then Expected(Name); Value := ;

while IsAlNum(Look) do begin

Value := Value + UpCase(Look);

GetChar; end;

SkipWhite; end;

{ Get a Number } function GetNum: integer; var Val: integer; begin

NewLine;

if not IsDigit(Look) then Expected(Integer);

Val := 0;

while IsDigit(Look) do begin

Val := 10 * Val + Ord(Look) - Ord(0);

GetChar; end;

GetNum := Val; SkipWhite; end;

{ Get an Identifier and Scan it for Keywords }

procedure Scan;

begin

GetName;

Token := KWcode[Lookup(Addr(KWlist), Value, NKW) + 1]; end;