反思 – Scala相当于C#的Expression API

发布时间：2020-12-16 09:20:04 所属栏目：安全来源：网络整理

导读：他们在 Scala中是否等同于C#的Expression API？例如,我想有一个这样的lambda： (Foo) = Foo.bar 并且能够在传递给它的功能中访问“bar”. 解决方法 Scala不支持此功能. ScalaQL: Language-Integrated Database Queries for Scala在Scala中描述了类似LINQ的

他们在 Scala中是否等同于C#的Expression API？

例如,我想有一个这样的lambda：

(Foo) => Foo.bar

并且能够在传递给它的功能中访问“bar”.

解决方法

Scala不支持此功能. ScalaQL: Language-Integrated Database Queries
for Scala在Scala中描述了类似LINQ的功能：

While it is possible for Microsoft to
simply extend their language with this
particular feature,lowly application
developers are not so fortunate. For
exam- ple,there is no way for anyone
(outside of Sun Microsystems) to
implement any form of LINQ within Java
because of the language modications
which would be required. We faced a
similar problem attempting to
implement LINQ in Scala.

Fortunately,Scala is actually powerful enough in and of itself to implement a form of LINQ even without adding support for expression trees. Through a combination of operator overloading,implicit conversions,and controlled call- by-name semantics,we have been able to achieve the same eect without making any changes to the language itself.

（编辑：李大同）

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