_Y_ on Scala Feels like EJB 2

Comment on Scala Feels like EJB 2 parent

Heh to a Java programmer, the answer would be - everything.

Here are my thoughts on it. - I get val myList is some sort of list... - Seems to be a list of Strings. But what is ::? - Nil means list is nullable. Wait is one of the parts of list 'myList(println)' (looks a bit like Smalltalk)? - Why is println the argument and not the method? Is that syntax correct?!

Compare same thing in Fantom. Note ; is only used as a separator and is equal in all respects to '\n'.

     myList := ["Jim", "Bob", null]; echo(myList)

pivo 14y

The :: is Scala's cons operator, the Nil means end-of-list. It's actually much more common in Scala to create a list like so:

  val nn = List("Jim","Bob")

This creates the same list that the example using :: did. It doesn't need to be explicitly terminated with Nil.

_Y_14y

What does cons operator mean? Concatenation? Constructor? Other than hello world I haven't done much Scala.

tvorryn 14y

Cons is short for construct and comes from Lisp which has weird names for things; things like car and cdr.

It means construct a new list.

A cons A (or A :: B) means create a new list with A before B, where B can be a list item or a list itself and A is a list item.

The :: operator is right associative so "Jim" :: "Bob" :: Nil actually works like ("Jim" :: ("Bob" :: Nil) ) (Actually all operators that end in : are right associative in Scala.)

For more see: http://en.wikipedia.org/wiki/Cons

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