keyword

In the following piece of code (taken from the Groovy Semantics Manual page ), why prefix the assignment with the keyword def ? def x = 0 def y = 5 while ( y-- > 0 ) { println "" + x + " " + y x++ } assert x == 5 The def keyword can be removed, and this snippet would produce the same results. So what's the effect of the keyword def ? It's syntactic sugar for basic scripts. Omitting the "def" keyword puts the variable in the bindings for the current script and groovy treats it (mostly) like a globally scoped variable: x = 1 assert x == 1 assert this.binding.getVariable("x") == 1 Using the def

When must we use extern alias keyword in C#? Basically you only really need it when you want to use two types with the same fully qualified name (same namespace, same type name) from different assemblies. You declare a different alias for each assembly, so you can then reference them via that alias. Needless to say, you should try to avoid getting into that situation to start with :) It's there to help you hoist yourself out of a really deep hole dug by versioning. Say your first version of your program uses this class using System; namespace Acme.Financial.Banking { [Serializable] public

In C#, I can do the following: int @private = 15; And in VB.NET, I can do the following: Dim [Private] As Integer = 15 I am wondering if there is a way in F# to use reserved keywords as identifiers, like there is in VB.NET and C#? Jon Skeet Given section 3.4 of the F# 2.0 spec : Identifiers follow the specification below. Any sequence of characters that is enclosed in double-backtick marks (`` ``), excluding newlines, tabs, and double-backtick pairs themselves, is treated as an identifier. I suspect you can put it in backticks: ``private`` I haven't tried it though. 来源： https://stackoverflow

I have a very simple question - when should we apply the new keyword when creating objects in Scala? Is it when we try to instantiate Java objects only? Use the new keyword when you want to refer to a class 's own constructor: class Foo { } val f = new Foo Omit new if you are referring to the companion object's apply method: class Foo { } object Foo { def apply() = new Foo } // Both of these are legal val f = Foo() val f2 = new Foo If you've made a case class: case class Foo() Scala secretly creates a companion object for you, turning it into this: class Foo { } object Foo { def apply() = new

This question already has an answer here: Manually raising (throwing) an exception in Python 7 answers I have read the official definition of "raise", but I still don't quite understand what it does. In simplest terms, what is "raise"? Example usage would help. Ignacio Vazquez-Abrams It has 2 purposes. yentup has given the first one. It's used for raising your own errors. if something: raise Exception('My error!') The second is to reraise the current exception in an exception handler, so that it can be handled further up the call stack. try: generate_exception() except SomeException as e: if