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Comment by munificent | Hacker News Reader

It's interesting to see how far C# progressed since this was written. Just a couple of years later, C# 3.0 came out and his example becomes:

    mylist.Select(foo => foo.Description())
          .Where(x => x != "")
          .Aggregate((a, b) => a + "\n" + b);

Which is, I think, pretty nice.

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It gets better, though. C# 3.0 also has query expressions, which are even closer to Python's list comprehensions. Also, I think String.Join(sep, enumerable) would be more efficient than repeated string concatenation with + (given that C# strings are immutable, it'd have to reallocate and copy bytes each time, just like in Python).

So we'd have:

   String.Join("\n", from x in mylist where x.Description() != ""
                     select x.Description());

Hardly looks like a statically typed language anymore, does it?

There is String.Join also used in the article but now there is a overload accepting IEnumerable<String>.

  String.Join("\n", mylist.Select(foo => foo.Description()).Where(x => x != ""));

Using a method group yields an even more readable code. Okay, it depends - if you are not used to method groups, it looks a bit strange but I like it.

  String.Join("\n", mylist.Select(x => x.Description()).Where(String.IsNullOrEmpty));

Note that I slightly changed and inverted the predicate because there is no build-in String.IsNotNullOrEmpty but you could of course write it yourself. I have a small extension method in my tool library that wraps String.Join and takes care of filtering out null references and empty and white space-only strings.

  mylist.Select(item => item.Description()).JoinExcludingNullOrWhitespace("\n");

Wow, that's interesting. Is 'x' just a magic var for whatever Select() yields in each iteration?

x is the input variable to that anonymous function.

Instead of the named syntax e.g. doSomething(x) { return x * x; } the syntax for C# anonymous functions is x => x * x

The argument to Where() is a Func<TSource, Boolean>, and that "x => x .. " business is C#'s lambda syntax. x is just a variable name, no magic there.

It's a lambda. Saying x => foo(x) is the same as lambda x: foo(x) from Python.

x is the variable in the anonymous function 'x => x != ""'. I don't know C# but I presume that everything before '=>' is the argument list and the rest is the function body (with implicit return).

You can see it again in '(a, b) => a + "\n" + b'.

As a side note, I find it a bit funny how C# chooses method names in Linq for the benefit of programmers who know SQL, despite `Select`, `Where`, and `Aggregate` acting exactly like what other functional languages would call `map`, `filter`, and `reduce`. Not wrong, just sort of quirky.

JavaScript will use the same "fat arrow" syntax for anonymous functions in ES6:

http://css.dzone.com/articles/javascript-fat-city

Coffeescript uses it already.

> `Select`, `Where`, and `Aggregate` acting exactly like what other functional languages would call `map`, `filter`, and `reduce`. Not wrong, just sort of quirky.

Or `collect`, `findAll`, and `inject`.

Yeah, I don't know what the precedent is for Ruby's versions. I'm glad map, filter and reduce are also present.

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