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.
language-features
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questions
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How to loop through all enum values in C#? [duplicate]
This question already has an answer here:
How do I enumerate an enum in C#? 26 answers
public enum Foos
{
A,
B,
C
}
Is there a way to loop through the possible values of Foos?
...
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514
votes
11
answers
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views
What is the python "with" statement designed for?
I came across the Python with statement for the first time today. I've been using Python lightly for several months and didn't even know of its existence! Given its somewhat obscure status, I ...
- 57.9k
480
votes
21
answers
83k
views
Expression versus Statement
I'm asking with regards to C#, but I assume it's the same in most other languages.
Does anyone have a good definition of expressions and statements and what the differences are?
user1684
477
votes
28
answers
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Why Doesn't C# Allow Static Methods to Implement an Interface?
Why was C# designed this way?
As I understand it, an interface only describes behaviour, and serves the purpose of describing a contractual obligation for classes implementing the interface that ...
- 8,409
473
votes
22
answers
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views
What does the 'static' keyword do in a class?
To be specific, I was trying this code:
package hello;
public class Hello {
Clock clock = new Clock();
public static void main(String args[]) {
clock.sayTime();
}
}
But it ...
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427
votes
6
answers
156k
views
What's the difference between interface and @interface in java?
I haven't touched Java since using JBuilder in the late 90's while at University, so I'm a little out of touch - at any rate I've been working on a small Java project this week, and using Intellij ...
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417
votes
17
answers
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views
JavaScript hashmap equivalent
As made clear in update 3 on this answer, this notation:
var hash = {};
hash[X]
does not actually hash the object X; it actually just converts X to a string (via .toString() if it's an object, or ...
- 227k
388
votes
33
answers
71k
views
Are there legitimate uses for JavaScript's "with" statement?
Alan Storm's comments in response to my answer regarding the with statement got me thinking. I've seldom found a reason to use this particular language feature, and had never given much thought to how ...
346
votes
13
answers
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views
How to correctly use lists?
Brief background: Many (most?) contemporary programming languages in widespread use have at least a handful of ADTs [abstract data types] in common, in particular,
string (a sequence comprised of ...
- 69.6k
314
votes
13
answers
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DateTime.Now vs. DateTime.UtcNow
I've been wondering what exactly are the principles of how the two properties work. I know the second one is universal and basically doesn't deal with time zones, but can someone explain in detail how ...
- 15.3k
255
votes
7
answers
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How does "this" keyword work within a function?
I just came across an interesting situation in JavaScript. I have a class with a method that defines several objects using object-literal notation. Inside those objects, the this pointer is being ...
- 25.6k
225
votes
8
answers
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views
Is SQL or even TSQL Turing Complete?
This came up at the office today. I have no plans of doing such a thing, but theoretically could you write a compiler in SQL? At first glance it appears to me to be turing complete, though extremely ...
- 27.5k
201
votes
12
answers
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views
Why doesn't a python dict.update() return the object?
I have this code:
award_dict = {
"url": "http://facebook.com",
"imageurl": "http://farm4.static.flickr.com/3431/3939267074_feb9eb19b1_o.png",
"...
- 49.7k
175
votes
13
answers
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What are the differences between "generic" types in C++ and Java?
Java has generics and C++ provides a very strong programming model with templates.
So then, what is the difference between C++ and Java generics?
- 12.3k
159
votes
17
answers
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Is there more to an interface than having the correct methods
So lets say I have this interface:
public interface IBox
{
public void setSize(int size);
public int getSize();
public int getArea();
//...and so on
}
And I have a class that implements ...
- 265k
158
votes
10
answers
9k
views
Why are private fields private to the type, not the instance?
In C# (and many other languages) it's perfectly legitimate to access private fields of other instances of the same type. For example:
public class Foo
{
private bool aBool;
public void DoBar(...
- 11.6k
153
votes
10
answers
30k
views
What is the tilde (~) in the enum definition?
I'm always surprised that even after using C# for all this time now, I still manage to find things I didn't know about...
I've tried searching the internet for this, but using the "~" in a search isn'...
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152
votes
2
answers
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views
Conditional/ternary operator for assignments in Python? [duplicate]
C and many other languages have a conditional (AKA ternary) operator. This allows you to make very terse choices between two values based on the truth of a condition, which makes expressions, ...
- 74.8k
141
votes
3
answers
66k
views
VB.NET equivalent of C# property shorthand?
Is there a VB.NET equivalent to the C#:
public string FirstName { get; set; }
I know you can do
Public Property name() As String
Get
Return _name.ToString
End Get
Set(ByVal value As ...
- 2,173
129
votes
12
answers
32k
views
Why is there a `null` value in JavaScript?
In JavaScript, there are two values which basically say 'I don't exist' - undefined and null.
A property to which a programmer has not assigned anything will be undefined, but in order for a property ...
- 167k
128
votes
6
answers
175k
views
Use of Begin / End Blocks and the Go keyword in SQL Server?
What are the guidelines as to when to use the BEGIN and END keywords in SQL Server?
Also, what exactly does the GO keyword do?
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123
votes
9
answers
75k
views
What is the purpose of python's inner classes?
Python's inner/nested classes confuse me. Is there something that can't be accomplished without them? If so, what is that thing?
114
votes
5
answers
17k
views
The written versions of the logical operators
This is the only place I've ever seen and, or and not listed as actual operators in C++. When I wrote up a test program in NetBeans, I got the red underlining as if there was a syntax error and ...
- 2,492
110
votes
36
answers
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Hidden features of HTML
HTML being the most widely used language (at least as a markup language) has not gotten its due credit.
Considering that it has been around for so many years, things like the FORM / INPUT controls ...
100
votes
8
answers
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views
What unique features does Firebug have that are not built-in to Firefox?
I just cleaned my Firefox addons and wondered:
Which features does Firebug have that make it unique?
Which features are available in both Firebug and the Firefox Developer Tools?
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votes
18
answers
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views
Samples of Scala and Java code where Scala code looks simpler/has fewer lines?
I need some code samples (and I also really curious about them) of Scala and Java code which show that Scala code is more simple and concise then code written in Java (of course both samples should ...
- 65.2k
95
votes
8
answers
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views
Python: How to pass more than one argument to the property getter?
Consider the following example:
class A:
@property
def x(self): return 5
So, of course calling the a = A(); a.x will return 5
But imagine that you want to be able to modify the property x.
...
- 3,083
86
votes
3
answers
17k
views
Why isn't the eigenclass equivalent to self.class, when it looks so similar?
I've missed the memo somewhere, and I hope you'll explain this to me.
Why is the eigenclass of an object different from self.class?
class Foo
def initialize(symbol)
eigenclass = class << ...
- 30.2k
85
votes
9
answers
31k
views
Why C# doesn't implement indexed properties?
I know, I know... Eric Lippert's answer to this kind of question is usually something like "because it wasn't worth the cost of designing, implementing, testing and documenting it".
But still, I'd ...
- 290k
83
votes
18
answers
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views
What are C macros useful for?
I have written a little bit of C, and I can read it well enough to get a general idea of what it is doing, but every time I have encountered a macro it has thrown me completely. I end up having to ...
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75
votes
4
answers
27k
views
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
...
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70
votes
4
answers
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views
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, ...
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69
votes
12
answers
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views
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?
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69
votes
5
answers
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views
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?
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votes
5
answers
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views
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 ...
- 1,259
62
votes
8
answers
18k
views
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 ...
- 61.6k
62
votes
1
answer
1k
views
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>(T obj, Func&...
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58
votes
9
answers
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views
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 ...
- 7,423
54
votes
5
answers
38k
views
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 ...
- 4,847
52
votes
6
answers
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views
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 ...
- 89.9k
49
votes
6
answers
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views
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 ...
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48
votes
4
answers
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views
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
...
- 1,334
47
votes
7
answers
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views
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 ...
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votes
5
answers
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views
44
votes
2
answers
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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 ...
- 24.8k
43
votes
1
answer
16k
views
Why doesn't Java varargs support collections?
In my Java code I often use the very handy method(Class... args) varargs. As far as I know, they allow you to pass any amount of Class objects or an array of Class[]. Since I also often use the Java ...
- 1,972
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votes
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answers
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What is the difference between VB and VBScript
What is the difference between VB and VBScript?
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Have you ever restricted yourself to using a subset of language features? [closed]
Have you ever restricted yourself to using a subset of language features, and more importantly, why?
I'm curious to find out who choose to use only certain language features and avoid others in order ...
38
votes
3
answers
12k
views
Java's switch equivalent in Clojure?
Is there an equivalent for Java's switch construct in Clojure? If yes, what is it? If no, do we have to use if else ladder to achieve it?
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votes
1
answer
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What's the new way to iterate over a Java Map in Scala 2.8.0?
How does scala.collection.JavaConversions supercede the answers given in Stack Overflow question Iterating over Java collections in Scala (it doesn't work because the "jcl" package is gone) and in ...
- 11.6k