我需要一个快速的运行时表达式解析器 [英] I need a fast runtime expression parser

问题描述

我需要找到一个快速、轻量级的表达式解析器.

I need to locate a fast, lightweight expression parser.

理想情况下，我想向它传递一个名称/值对列表(例如变量)和一个包含要计算的表达式的字符串.我所需要的只是一个真/假值.

Ideally I want to pass it a list of name/value pairs (e.g. variables) and a string containing the expression to evaluate. All I need back from it is a true/false value.

表达式的类型应该遵循:

The types of expressions should be along the lines of:

varA == "xyz" and varB==123

基本上，只是一个简单的逻辑引擎，其表达式在运行时提供.

Basically, just a simple logic engine whose expression is provided at runtime.

更新
至少它需要支持 ==, !=, >, >=, <, <=

UPDATE
At minimum it needs to support ==, !=, >, >=, <, <=

关于速度，我预计每个请求大约执行 5 个表达式.我们会看到每秒 100 个/请求附近的某个地方.我们当前的页面往往在 50 毫秒内执行.通常任何表达式中只涉及 2 或 3 个变量.但是，在执行之前，我需要将大约 30 个加载到解析器中.

Regarding speed, I expect roughly 5 expressions to be executed per request. We'll see somewhere in the vicinity of 100/requests a second. Our current pages tend to execute in under 50ms. Usually there will only be 2 or 3 variables involved in any expression. However, I'll need to load approximately 30 into the parser prior to execution.

更新 2012/11/5
关于性能的更新.我们在将近 2 年前实施了 nCalc.从那时起，我们扩展了它的用途，以便我们平均覆盖 300 多个变量的 40 多个表达式在回传中.现在每秒发生数千次回传，性能下降绝对为零.

UPDATE 2012/11/5
Update about performance. We implemented nCalc nearly 2 years ago. Since then we've expanded it's use such that we average 40+ expressions covering 300+ variables on post backs. There are now thousands of post backs occurring per second with absolutely zero performance degradation.

我们还对其进行了扩展，以包含一些附加功能，同样没有性能损失.简而言之，nCalc 满足了我们的所有需求并超出了我们的预期.

We've also extended it to include a handful of additional functions, again with no performance loss. In short, nCalc met all of our needs and exceeded our expectations.

推荐答案

你见过 https://ncalc.codeplex.com/ 和 https://github.com/sheetsync/NCalc ?

它可扩展、快速(例如，有自己的缓存)使您能够在运行时通过处理 EvaluateFunction/EvaluateParameter 事件提供自定义函数和变量.它可以解析的示例表达式:

It's extensible, fast (e.g. has its own cache) enables you to provide custom functions and varaibles at run time by handling EvaluateFunction/EvaluateParameter events. Example expressions it can parse:

Expression e = new Expression("Round(Pow(Pi, 2) + Pow([Pi2], 2) + X, 2)");

  e.Parameters["Pi2"] = new Expression("Pi * Pi");
  e.Parameters["X"] = 10;

  e.EvaluateParameter += delegate(string name, ParameterArgs args)
    {
      if (name == "Pi")
      args.Result = 3.14;
    };

  Debug.Assert(117.07 == e.Evaluate());

它还处理 unicode &许多数据类型本机.如果您想更改语法，它会附带一个鹿角文件.还有一个 fork 支持 MEF 加载新功能.

It also handles unicode & many data type natively. It comes with an antler file if you want to change the grammer. There is also a fork which supports MEF to load new functions.

它还支持逻辑运算符、日期/时间字符串和 if 语句.

It also supports logical operators, date/time's strings and if statements.

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