[Indigo]<AlgebraStructures>NewAlgebraStructures>ASVariableSetsImpl.mesa!1

ASVariableSetsImpl.mesa

Last Edited by: Arnon, April 28, 1987 9:22:39 am PDT

DIRECTORY

Rope,

IO,

MathExpr,

MathConstructors,

AlgebraClasses,

Structures,

Variables,

Sets;

ASVariableSetsImpl: CEDAR PROGRAM

IMPORTS Rope, IO, MathConstructors, AlgebraClasses, Structures, Variables

EXPORTS Sets =

BEGIN OPEN AC: AlgebraClasses, VARS: Variables, Sets;

Errors and Types

SyntaxError: PUBLIC ERROR [reason: ATOM] = CODE;

BadUniverse: PUBLIC ERROR [universe: AC.Object] = CODE;

TypeError: PUBLIC ERROR [message: ATOM ← $Unspecified] = CODE;

Method: TYPE = AC.Method;

Object: TYPE = AC.Object;

Operations

VariableFromRope: PUBLIC AC.FromRopeOp ~ {

variable: Object ← VARS.FromRope[in, VARS.Variables];

set: Object ← MakeSet[LIST[variable], VariableSets];

singleSetStructure: Object ← MakeSingleSetStructure[set];

RETURN[SSSEltFromUnderlyingSetUniverseElt[variable, singleSetStructure] ];

};

Start Code

Kludge up special subclass for VariableSets, containing special evaluation for variables

VariableSets: PUBLIC AC.Object ← MakePowerSetStructure[VARS.Variables]; -- this is initialization only; n.b. must be done after familyOfSetsClass initialized, so that gets it as non-NIL class, so that class pointer in variableSetsClass points to something non-NIL as superclass.

variableMethod: Method ← AC.MakeMethod[FromRopeOp, FALSE, NEW[AC.FromRopeOp ← VariableFromRope], NIL, "variable"];

variableSetsClass: AC.Object ← AC.MakeClass["variableSetsClass", VariableSets.class, NIL];

AC.AddMethodToClass[$variable, variableMethod, variableSetsClass];

VariableSets.class ← variableSetsClass;

AC.InstallStructure[VariableSets]; -- update value of VariableSets installed by MakeFamilyOfSetsStructure; now its class is not just the standard one, but a subclass containing variableMethod.

END.