ISPARQLExpression.cs

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using System.Collections.Generic;

namespace VDS.RDF.Query.Expressions
{
    
    

    /// <summary>
    /// SPARQL Expression Types.
    /// </summary>
    public enum SparqlExpressionType
    {
        /// <summary>
        /// The Expression is a Primary Expression which is a leaf in the expression tree
        /// </summary>
        Primary,
        /// <summary>
        /// The Expression is a Unary Operator which has a single argument
        /// </summary>
        UnaryOperator,
        /// <summary>
        /// The Expression is a Binary Operator which has two arguments
        /// </summary>
        BinaryOperator,
        /// <summary>
        /// The Expression is a Function which has zero/more arguments
        /// </summary>
        Function,
        /// <summary>
        /// The Expression is an Aggregate Function which has one/more arguments
        /// </summary>
        Aggregate,
        /// <summary>
        /// The Expression is a Set Operator where the first argument forms the LHS and all remaining arguments form a set on the RHS
        /// </summary>
        SetOperator,
        /// <summary>
        /// The Expression is a Unary Operator that applies to a Graph Pattern
        /// </summary>
        GraphOperator,
    }

    /// <summary>
    /// Interface for SPARQL Expression Terms that can be used in Expression Trees while evaluating Sparql Queries.
    /// </summary>
    public interface ISparqlExpression
    {
        /// <summary>
        /// Accept a <see cref="ISparqlExpressionProcessor{TResult,TContext,TBinding}"/> by calling the appropriate method on its interface for this expression.
        /// </summary>
        /// <typeparam name="TResult">Type of result that the process method returns.</typeparam>
        /// <typeparam name="TContext">The type of the context parameter to the process method.</typeparam>
        /// <typeparam name="TBinding">The type of the binding parameter of the process method.</typeparam>
        /// <param name="processor">The processor to be invoked.</param>
        /// <param name="context">The context object to use for processing.</param>
        /// <param name="binding">The binding to be processed.</param>
        /// <returns></returns>
        TResult Accept<TResult, TContext, TBinding>(ISparqlExpressionProcessor<TResult, TContext, TBinding> processor, TContext context, TBinding binding);

        /// <summary>
        /// Accept a <see cref="ISparqlExpressionVisitor{T}"/> by calling the appropriate method on its interface for this expression.
        /// </summary>
        /// <typeparam name="T">Type of result that the called method returns.</typeparam>
        /// <param name="visitor">The visitor to be invoked.</param>
        /// <returns>The result of calling the method on the visitor.</returns>
        T Accept<T>(ISparqlExpressionVisitor<T> visitor);

        /// <summary>
        /// Gets an enumeration of all the Variables used in an expression.
        /// </summary>
        IEnumerable<string> Variables
        {
            get;
        }

        /// <summary>
        /// Gets the SPARQL Expression Type.
        /// </summary>
        SparqlExpressionType Type
        {
            get;
        }

        /// <summary>
        /// Gets the Function Name or Operator Symbol - function names may be URIs of Keywords or the empty string in the case of primary expressions.
        /// </summary>
        string Functor
        {
            get;
        }

        /// <summary>
        /// Gets the Arguments of this Expression.
        /// </summary>
        IEnumerable<ISparqlExpression> Arguments
        {
            get;
        }

        /// <summary>
        /// Transforms the arguments of the expression using the given transformer.
        /// </summary>
        /// <param name="transformer">Expression Transformer.</param>
        /// <returns></returns>
        ISparqlExpression Transform(IExpressionTransformer transformer);

        /// <summary>
        /// Gets whether an expression can safely be evaluated in parallel.
        /// </summary>
        bool CanParallelise
        {
            get;
        }
    }
}