/// <summary>
/// Creates a new query that applies an accumulator function over a sequence. The specified seed value is used as the initial accumulator value.
/// </summary>
/// <typeparam name="TSource">The type of the elements of source.</typeparam>
/// <typeparam name="TAcc">The type of the accumulator value.</typeparam>
/// <param name="query">An query whose values are used to aggregate over.</param>
/// <param name="seed">The initial accumulator value.</param>
/// <param name="func">An accumulator function to be invoked on each element.</param>
/// <returns>A query that returns the final accumulator value.</returns>
public static IQueryExpr <TAcc> Aggregate <TSource, TAcc>(this IQueryExpr <IEnumerable <TSource> > query, TAcc seed, Expression <Func <TAcc, TSource, TAcc> > func)
{
return(new QueryExpr <TAcc>(QExpr.NewAggregate(Expression.Constant(seed), func, query.Expr)));
}
