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Questions tagged [language-features]

A language feature is a distinct aspect of a programming language, such as binding rules, lexical design, or facets of the type system.

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Python type() or __class__, == or is

I want to test whether an object is an instance of a class, and only this class (no subclasses). I could do it either with: obj.__class__ == Foo obj.__class__ is Foo type(obj) == Foo type(obj) is Foo Are there reasons to choose one over another?…
mgibsonbr
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What's the difference between a hash and hash reference in Perl?

I would like to properly understand hashes in Perl. I've had to use Perl intermittently for quite some time and mostly whenever I need to do it, it's mostly related to text processing. And everytime, I have to deal with hashes, it gets messed up. I…
user855
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Will a future version of .NET support tuples in C#?

.Net 3.5 doesn't support tuples. Too bad, But not sure whether the future version of .net will support tuples or not?
Graviton
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Double dispatch in C#?

I have heard/read the term but don't quite understand what it means. When should I use this technique and how would I use it? Can anyone provide a good code sample?
Oded
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Why does Java permit escaped unicode characters in the source code?

I recently learned that Unicode is permitted within Java source code not only as Unicode characters (eg. double π = Math.PI; ) but also as escaped sequences (eg. double \u03C0 = Math.PI; ). The first variant makes sense to me - it allows programmers…
Zaven Nahapetyan
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Problem understanding C# type inference as described in the language specification

The C# language specification describes type inference in Section §7.5.2. There is a detail in it that I don’t understand. Consider the following case: // declaration void Method(T obj, Func func); // call Method("obj", s => (object)…
Timwi
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Javascript as a functional language

I am looking get to grips with functional programming concepts. I've used Javascript for many years for client side scripting in web applications and apart from using prototypes it was all simple DOM manipulation, input validation etc. Of late, I…
Ash
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Why isn't there an endianness modifier in C++ like there is for signedness?

(I guess this question could apply to many typed languages, but I chose to use C++ as an example.) Why is there no way to just write: struct foo { little int x; // little-endian big long int y; // big-endian short z; // native…
Lena Schimmel
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C# method call with parameter name and colon

I've begun to notice at times when I'm making method calls in C# that the names of the parameters for the method I'm calling will show up in the intellisense list appended with a colon, and that I can then format the method call…
Zann Anderson
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What is a maximum number of arguments in a Python function?

It's somewhat common knowledge that Python functions can have a maximum of 256 arguments. What I'm curious to know is if this limit applies to *args and **kwargs when they're unrolled in the following manner: items = [1,2,3,4,5,6] def…
Soviut
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Methods in Ruby: objects or not?

Inspired by this discussion, after some googling I wasn't able to find an answer to a pretty simple question regarding methods in Ruby: are methods objects or not? There are different opinions here and there, and I would really like to hear, let's…
Mladen Jablanović
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What is the purpose of long, double, byte, char in Java?

So I'm learning java, and I have a question. It seems that the types int, boolean and string will be good for just about everything I'll ever need in terms of variables, except perhaps float could be used when decimal numbers are needed in a…
Ali
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Why do enums have computed properties but not stored properties in Swift?

I am new to Swift and just came across this in the documentation: Computed properties are provided by classes, structures, and enumerations. Stored properties are provided only by classes and structures. Why is that? Do associated values for…
Adit Gupta
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Anonymous type and tuple

What is the difference between anonymous type and tuple?
Amutha
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Equivalent of Class Loaders in .NET

Does anyone know if it possible to define the equivalent of a "java custom class loader" in .NET? To give a little background: I am in the process of developing a new programming language that targets the CLR, called "Liberty". One of the features…
Scott Wisniewski
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