Copyright (c) 2000 California Institute of Technology
All rights reserved. See the file COPYRIGHT for a full description.
$Id: Pos.m3,v 1.2 2001-09-19 15:13:58 wagner Exp $
MODULE Pos;
IMPORT Rule;
IMPORT Fmt;
PROCEDURE Compare(a, b: T): [-1 .. 1] =
VAR
arnum := Rule.Number(a.rule);
brnum := Rule.Number(b.rule);
BEGIN
IF arnum > brnum THEN
RETURN 1;
ELSIF arnum < brnum THEN
RETURN -1;
ELSIF a.index > b.index THEN
RETURN 1;
ELSIF a.index < b.index THEN
RETURN -1;
ELSE
RETURN 0;
END;
END Compare;
PROCEDURE Equal(a, b: T): BOOLEAN =
BEGIN
RETURN Compare(a, b) = 0;
END Equal;
PROCEDURE Hash(a: T): INTEGER =
BEGIN
RETURN Rule.Number(a.rule) + a.index*23;
END Hash;
PROCEDURE Format(a: T): TEXT =
BEGIN
IF a.rule # NIL THEN
RETURN Fmt.Int(a.rule.number) & ":" &
Fmt.Int(a.index);
ELSIF a.index = 0 THEN
RETURN "N";
ELSE
<* ASSERT a.index = -1 *>
RETURN "E";
END;
END Format;
PROCEDURE Zero(rule: Rule.T): T =
BEGIN
RETURN T{rule := rule,
cell := rule.syms,
index := 0};
END Zero;
PROCEDURE Advance(a: T): T =
BEGIN
RETURN T{rule := a.rule,
cell := a.cell.tail,
index := a.index + 1};
END Advance;
BEGIN
END Pos.