Try this: val dup = List(1,1,1,2,3,4,5,5,6,100,101,101,102) dup.groupBy(identity).collect { case (x, List(_,_,_*)) => x } The groupBy associates each distinct integer with a list of its occurrences. The collect is basically map where non-matching elements are ignored. The match pattern following case will match integers x that are associated with a list that fits the pattern … Read more
To see why you get the particular answers that arise, the desugaring explanations are very helpful. Let me supplement them with a little general advice about developing perceptions of Haskell code. Haskell’s type system makes no distinction between two separable “moral” purposes: [x] the type of values which are lists with elements drawn from x … Read more
Depending on what you want, there are two ways to do this: If you want to do this in “Edit mode”: You must enable “Edit mode” on the list before a selection matters. From the interface for List: /// Creates an instance. /// /// – Parameter selection: A selection manager that identifies the selected row(s). … Read more
[input[i:i+n] for i in range(0, len(input), n)] # Use xrange in py2k where n is the length of a chunk. Since you don’t define what might happen to the final element of the new list when the number of elements in input is not divisible by n, I assumed that it’s of no importance: with … Read more
>>> from itertools import groupby >>> L = [0, 0, 0, 3, 3, 2, 5, 2, 6, 6] >>> grouped_L = [(k, sum(1 for i in g)) for k,g in groupby(L)] >>> # Or (k, len(list(g))), but that creates an intermediate list >>> grouped_L [(0, 3), (3, 2), (2, 1), (5, 1), (2, 1), (6, … Read more
Very similar to @Eastsun’s, but a bit more intention revealing. Tested in Scala 2.8. scala> val l = List(1, 2, 3) l: List[Int] = List(1, 2, 3) scala> Stream.continually(l.toStream).flatten.take(10).toList res3: List[Int] = List(1, 2, 3, 1, 2, 3, 1, 2, 3, 1) Alternatively, with Scalaz: scala> import scalaz._ import scalaz._ scala> import Scalaz._ import Scalaz._ … Read more
These functions are in the CL package, you will need to (require ‘cl) to use them: (remove-if-not #’evenp ‘(1 2 3 4 5)) This will return a new list with all even numbers from the argument. Also look up delete-if-not, which does the same, but modifies its argument list.
The ListLike package seems to provide what you’re looking for. I’ve never understood why it isn’t more popular. ListLike aside, one reason this isn’t implemented in the Prelude is because it’s not possible to do so well without invoking some language extensions (multi-param type classes and fundeps or associated types). There are three sorts of … Read more
You can check multiple conditions inside the same square brackets: /Location/Addr[State=”TX” or State=”AL” or State=”MA”] Or if you have a really long list, you can create a list of states and use the contains() function. /Location/Addr[contains(‘TX AL MA’, State)] This will work fine for two-letter state abbreviations. If you want to make it more robust … Read more