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A function is a mapping from one set, called a domain, to another set, called the codomain. A function associates every element in the domain with exactly one element in the codomain. In Scala, both domain and codomain are types.
val square : Int => Int = x => x * x
Article by Faruk Ateş, [originally on KuraFire.net][original] which is currently down
One of the most commonly overlooked and under-refined elements of a website is its pagination controls. In many cases, these are treated as an afterthought. I rarely come across a website that has decent pagination, and it always makes me wonder why so few manage to get it right. After all, I'd say that pagination is pretty easy to get right. Alas, that doesn't seem the case, so after encouragement from Chris Messina on Flickr I decided to write my Pagination 101, hopefully it'll give you some clues as to what makes good pagination.
Before going into analyzing good and bad pagination, I want to explain just what I consider to be pagination: Pagination is any kind of control system that lets the user browse through pages of search results, archives, or any other kind of continued content. Search results are the o
val n = 9 | |
val s = Math.sqrt(n).toInt | |
type Board = IndexedSeq[IndexedSeq[Int]] | |
def solve(board: Board, cell: Int = 0): Option[Board] = (cell%n, cell/n) match { | |
case (r, `n`) => Some(board) | |
case (r, c) if board(r)(c) > 0 => solve(board, cell + 1) | |
case (r, c) => | |
def guess(x: Int) = solve(board.updated(r, board(r).updated(c, x)), cell + 1) | |
val used = board.indices.flatMap(i => Seq(board(r)(i), board(i)(c), board(s*(r/s) + i/s)(s*(c/s) + i%s))) |
// Released under MIT license: http://www.opensource.org/licenses/mit-license.php | |
$('[placeholder]').focus(function() { | |
var input = $(this); | |
if (input.val() == input.attr('placeholder')) { | |
input.val(''); | |
input.removeClass('placeholder'); | |
} | |
}).blur(function() { | |
var input = $(this); |
From time to time, Musk will send out an e-mail to the entire company to enforce a new policy or let them know about something that's bothering him. One of the more famous e-mails arrived in May 2010 with the subject line: Acronyms Seriously Suck:
There is a creeping tendency to use made up acronyms at SpaceX. Excessive use of made up acronyms is a significant impediment to communication and keeping communication good as we grow is incredibly important. Individually, a few acronyms here and there may not seem so bad, but if a thousand people are making these up, over time the result will be a huge glossary that we have to issue to new employees. No one can actually remember all these acronyms and people don't want to seem dumb in a meeting, so they just sit there in ignorance. This is particularly tough on new employees.
That needs to stop immediately or I will take drastic action - I have given enough warning over the years. Unless an acronym is approved by me, it should not enter the SpaceX glossary.
foobar, foo, bar, baz, qux, quux, corge, grault, garply, waldo, fred, plugh, xyzzy, thud
Prereq:
apt-get install zsh
apt-get install git-core
Getting zsh to work in ubuntu is weird, since sh
does not understand the source
command. So, you do this to install zsh
wget https://github.com/robbyrussell/oh-my-zsh/raw/master/tools/install.sh -O - | zsh
Miles Sabin recently opened a pull request fixing the infamous SI-2712. First off, this is remarkable and, if merged, will make everyone's life enormously easier. This is a bug that a lot of people hit often without even realizing it, and they just assume that either they did something wrong or the compiler is broken in some weird way. It is especially common for users of scalaz or cats.
But that's not what I wanted to write about. What I want to write about is the exact semantics of Miles's fix, because it does impose some very specific assumptions about the way that type constructors work, and understanding those assumptions is the key to getting the most of it his fix.
For starters, here is the sort of thing that SI-2712 affects:
def foo[F[_], A](fa: F[A]): String = fa.toString