Constraint.cs

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// -------------------------------------------------------------------------- 
// Project rROTOR                                                             
// -------------------------------------------------------------------------- 
// File: ConstraintList.cs                                                    
// Author:  Francisco Ortin - francisco.ortin@gmail.com                       
// Description:                                                               
//    Abstract class that represents any constraint to be part of a Method WriteType.
//       In our type system, methods could have constraints associated to be
//       satisfied every time it is invoked. This class represent the 
//       homogeneous treatment of the Composite desing pattern.
//    Implements Composite pattern [Component].                               
//    Implements Command pattern [Command].                               
// -------------------------------------------------------------------------- 
// Create date: 05-04-2007                                                    
// Modification date: 25-04-2007                                              

using System;
using System.Collections.Generic;
using System.Text;
using ErrorManagement;

namespace TypeSystem.Constraints {
    abstract public class Constraint {

        #region Fields
        private string typeExpression;

        private bool validTypeExpression = false;
        #endregion

        #region Properties
        public bool ValidTypeExpression {
            set { 
                if (!value)
                    this.typeExpression = this.BuildTypeExpressionString();
            }
        }
        #endregion


        public virtual bool isEmpty() { return false; }

        public override string ToString() {
            if (this.validTypeExpression)
                return this.typeExpression;
            return this.typeExpression = this.BuildTypeExpressionString();
        }

        protected abstract string BuildTypeExpressionString();

        public abstract Constraint CloneTypeVariables(IDictionary<TypeVariable, TypeVariable> typeVariableMappings, IList<EquivalenceClass> equivalenceClasses);

        public abstract TypeExpression Check(MethodType methodAnalyzed, TypeExpression actualImplicitObject, bool showInvocationMessage, 
            SortOfUnification activeSortOfUnification, Location location);
    }
}