Doncaster Meeting and Programming Puzzle

Went to Doncaster for an exam board today.

The meeting room had this very impressive chandelier, which lent a lot to the proceedings.

Spent some time chatting with Colin, the external examiner, about programming matters. We were talking about good practices, properties and get/set methods and the like, and a question occurred.

“Why do some types in C# have a Length property (for example String and Array) whereas others have a Count method (for example List)? Both of them do the same thing, so it seems to be silly to have different names for them.”

Colin and I think we know the answer. But do you?

Comments

[Jeff Martin]

I think the length is there because of tradition (previous languages) and not any particularly good reason.

[Jeff Martin]

Also a decent answer was posted to stack overflow:
http://stackoverflow.com/questions/300522/count-vs-length-vs-size-in-a-collection

[Joel]

Length seems to make more sense. Not sure really, maybe they're showing off.

Also, how long is a string? :P

[Pat]

Because C# was designed to teach children bad programming practise. That's what Warren and Darren told me anyway.

[David]

Personally i would think of strings and arrays as being horizontal (Robs theory on Arrays being a series of boxes to store things in), therefore length would be appropriate. Lists however imply a vertical structure therefore the counting the items within it makes more sence.

[Robert]

The List class is built using an array, the 'count' method returns how many items are actually stored in the array, but the 'capacity' method returns the actual length of the array.

Arrays and Strings are as long as the 'length' method says they are, but lists are not.

[Robert]

The List class is built using an array, the 'count' method returns how many items are actually stored in the array, but the 'capacity' method returns the actual length of the array.

Arrays and Strings are as long as the 'length' method says they are, but lists are not.

[Robert]

The List class is built using an array, the 'count' method returns how many items are actually stored in the array, but the 'capacity' method returns the actual length of the array.

Arrays and Strings are as long as the 'length' method says they are, but lists are not.

[Robert]

The List class is built using an array, the 'count' method returns how many items are actually stored in the array, but the 'capacity' method returns the actual length of the array.

Arrays and Strings are as long as the 'length' method says they are, but lists are not.

[Robert]

The List class is built using an array, the 'count' method returns how many items are actually stored in the array, but the 'capacity' method returns the actual length of the array.

Arrays and Strings are as long as the 'length' method says they are, but lists are not.

[Robert]

The List class is built using an array, the 'count' method returns how many items are actually stored in the array, but the 'capacity' method returns the actual length of the array.

Arrays and Strings are as long as the 'length' method says they are, but lists are not.

[arron]

id take a guess that 'list' is a linked list therefore it would be impossible to know the length without iterating - 'counting' - through the list, whereas the former is an array therefore the length is already known. This is coming from a c++ programer tho.

[Rob]

I think it is because the String and Array types have a particular length when they are created and this does not change. You can't adjust the length of an array, and you can't change the contents of a string, you can only make new ones. Therefore such a type can have a length property that can be looked up, i.e. there is no need to calculate anything.

On the other hand collection classes like Lists can have things added and removed at any time, so when you need to know how many they contain you have to go and count the items. This means that some code needs to run, and the designers of the classes indicate this by making the Count() behaviour a method, so that you know that some algorithm is running to work out the answer, rather than a simple look up.

I now have a rule when creating properties that if you aren't just looking up an answer you should use a method instead, so that the user of your classs knows when they are running code inside your object.

[Joel]

Strings can change length, when a person uses Console.Readline, they would be dictating the size of the String, then maybe, you would change the String length later on when you change its contents.

I may be wrong.

Cool info either way :D

[Simon Johnson]

To help assist code in making it friendly to those reading it without out prior knowledge of the language of course.