68 lines
2.3 KiB
C#
68 lines
2.3 KiB
C#
/*
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Copyright (c) Microsoft Corporation
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All rights reserved.
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Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in
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compliance with the License. You may obtain a copy of the License
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at http://www.apache.org/licenses/LICENSE-2.0
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THIS CODE IS PROVIDED *AS IS* BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, EITHER
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EXPRESS OR IMPLIED, INCLUDING WITHOUT LIMITATION ANY IMPLIED WARRANTIES OR CONDITIONS OF
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TITLE, FITNESS FOR A PARTICULAR PURPOSE, MERCHANTABLITY OR NON-INFRINGEMENT.
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See the Apache Version 2.0 License for specific language governing permissions and
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limitations under the License.
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*/
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using System;
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using System.Collections.Generic;
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using System.Text;
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using System.IO;
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using System.Reflection;
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using System.Linq;
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using System.Linq.Expressions;
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using System.Diagnostics;
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namespace Microsoft.Research.DryadLinq
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{
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// This class implements a simple evaluator for expression. It may
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// evolve into a better and more useful thing: a simplifier that
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// goes through an expression to remove all dependency to the
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// current local execution context. This is necessary to ensure
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// that expressions can be remotely executed. Even better, this
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// simplifier could detect potential "impure" expressions. Again,
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// it would be nice if this is a functionality provided by C# and
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// LINQ. But unfortunately it is not.
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internal abstract class ExpressionSimplifier
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{
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internal abstract object EvalBoxed(Expression expr);
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// Evaluate the expression in the current local execution context.
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internal static object Evaluate(Expression expr)
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{
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Type qType = typeof(ExpressionSimplifier<>).MakeGenericType(expr.Type);
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ExpressionSimplifier evaluator = (ExpressionSimplifier)Activator.CreateInstance(qType);
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return evaluator.EvalBoxed(expr);
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}
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}
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internal class ExpressionSimplifier<T> : ExpressionSimplifier
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{
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internal override object EvalBoxed(Expression expr)
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{
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return this.Eval(expr);
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}
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internal T Eval(Expression expr)
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{
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Expression<Func<T>> lambda = Expression.Lambda<Func<T>>(expr);
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Func<T> func = lambda.Compile();
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return func();
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}
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}
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}
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