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[Levi]

They are usually classes for a language.  Every language seems to do it a little different.

I dislike pythons implementation.  It doesn't seem to like it when I use arrays as keys.   

[kaenneth]

So I guess my real question is, do hashmaps and dictionaries exist as defined things in themselves in a programming language?  Or is it just a recognized construction, like an Object or Linked List, that has to be inferred through your coding methodology?

Because I do feel like I have a use for these pointers, I just don't know how to implement them.

.net provides them in the System.Collections.Generic namespace, dunno about other platforms, but I would presume so.
And it would be a bad idea to try to implement them yourself (except as an exercise, in which case I recommend it) as *cough* they put a lot of work into the inbuilt versions.

[Willfor]

http://msdn.microsoft.com/en-us/library/xfhwa508.aspx <- C# Dictionary, which is sort of a hashmap of its own but without the ability to return a null value.

http://stackoverflow.com/questions/1273139/c-sharp-java-hashmap-equivalent <- How to extend hashmap in a very useful way.

I've always seemed to run into problems with C#'s version of this thing.

[Max White]

So I guess my real question is, do hashmaps and dictionaries exist as defined things in themselves in a programming language?  Or is it just a recognized construction, like an Object or Linked List, that has to be inferred through your coding methodology?

Because I do feel like I have a use for these pointers, I just don't know how to implement them.

...
Linked Lists are things... As are Hash maps!

This is an example of using a linked list as a thing.

            LinkedList<int> listOfInts = new LinkedList<int>();

            listOfInts.AddFirst(3);
            listOfInts.AddFirst(2);
            listOfInts.AddFirst(1);
            listOfInts.AddLast(4);
            listOfInts.AddLast(5);

            Console.WriteLine("Contents of list");
            foreach (int i in listOfInts)
            {
                Console.WriteLine(i);
            }

[Aqizzar]

Linked Lists are things... As are Hash maps!

This is an example of using a linked list as a thing.

Yet another reason for why I must need a book.  When I searched for such information, I got stuff like this, and remembered from my Java days that "Linked List" is just a name for when you make an Object such that it includes in its body of data a reference point for another instance, so your objects stack like Russian dolls.  I had no idea C# includes such stuff as standard classes.

[Max White]

I'm pretty sure they are a thing in Java too...
C# has Dictionarys, LinkedLists, ArrayLists, HashSets and I'm pretty sure there are DataTrees in there somewhere as well.



It also has a thing called a List. It's not abstract, and acts just like how you would expect a list to act... Not sure how it stores data though.

[Stargrasper]

I'm pretty sure they are a thing in Java too...
C# has Dictionarys, LinkedLists, ArrayLists, HashSets and I'm pretty sure there are DataTrees in there somewhere as well.



It also has a thing called a List. It's not abstract, and acts just like how you would expect a list to act... Not sure how it stores data though.

I disappear for a day because of life and Aqizzar forgets what objects are...

In Java, LinkedList and all other datastructures are still objects.  How it stores data depends on what it is, but the important thing here is that LinkedList is a full-blown object.  List is actually an interface.  It doesn't store data.  Java interfaces are essentially a promise to implement methods with the included signatures.  You can't instantiate an instance of an interface, similar to how you can't instantiate an instance of an abstract class.  They also give you the ability to cast implementing objects to that interface.  Useful for storing in datastructures.  That theory is why you usually see me implementing ArrayList and LinkedList like this...both implement the List interface...

Code: [Select]

List<Object> l1 = new ArrayList<Object>();
List<Object> l2 = new LinkedList<Object>();


[Mego]

You kids and your fancy containers. Back in my day, all we had were arrays and structs! We couldn't even overload operators to make our code simpler and easier to read! Then, C++ and the STL came along, and we burned it at the stake for witchcraft!

Funny how I'm saying this despite probably being the youngest (or close to it) that posts in this thread.

[GlyphGryph]

So I guess my real question is, do hashmaps and dictionaries exist as defined things in themselves in a programming language?  Or is it just a recognized construction, like an Object or Linked List, that has to be inferred through your coding methodology?

Pretty much everything that is a "recognized construction" exists in some language or other. While "objects" may just be methodologies in some languages, in others (many) like Ruby they are THE central component that holds everything together. (In fact, Ruby is pretty much composed of objects and messages and that's it)

Sure, at the assembly level these things don't exist, but higher level languages are all about turning these recognized constructions into core parts of their design pattern.

On another note, I've really fallen badly in love with closures and duck typing. I'm going to be an unhappy camper if I ever again have to spend the bulk of my time programming in a language that doesn't have them.
In the other hand I did some hex editing by hand the other day, and that was also enjoyable...

[Mego]

Speaking of duck typing, does anyone have any clue how Boost worked their magic with boost::any?

[Max White]

List is actually an interface.

C# man, you always forget C#.
List is a class in c#, not an interface, and it isn't even an abstract class. You can make an instance of it and everything...

The interface that c# uses would be ICollection, for example

Code: [Select]

            ICollection<int> myCollection = new List<int>();
            myCollection = new LinkedList<int>();
            myCollection = new int[5];

[Aqizzar]

Once again, a lot of my confusion here comes from not knowing what exists in a particular language and what is just an academic term for a system that arises from your code.  It's kind of hard to talk about things like that, because in some languages, words like "object" or "list" or "construct" or "dictionary" are a tangible component with its own syntax, and in other languages they're not.

I really really need a dictionary.  Which is to say, a glossary of terms and descriptions for a language, not a list of data pointers.

[GlyphGryph]

Well, for ruby there's http://ruby-doc.org/
For C++ there is http://www.cplusplus.com/reference/

Though that doesn't include syntax level stuff like the ternary operator.

I imagine other languages have something similar.

[Max White]

Has anybody yet pointed you to the .net library? It has pretty much everything.

Otherwise, I'm sure between us if you ever want to know something, you have 24 hour tec support.

[Stargrasper]

List is actually an interface.

C# man, you always forget C#.
List is a class in c#, not an interface, and it isn't even an abstract class. You can make an instance of it and everything...

The interface that c# uses would be ICollection, for example

Code: [Select]

            ICollection<int> myCollection = new List<int>();
            myCollection = new LinkedList<int>();
            myCollection = new int[5];

Sorry, got confused since you were talking about two different languages in one post.

And yeah, Aqizzar, feel free to ask us anything.  I'm sure we know the answer to any question you will reasonably run into.