computer-science

Here on SO people sometimes say something like "you cannot parse X with regular expressions, because X is not a regular language". From my understanding however, modern regular expressions engines can match more than just regular languages in Chomsky's sense . My questions: given a regular expression engine that supports backreferences lookaround assertions of unlimited width recursion, like (?R) what kind of languages can it parse? Can it parse any context-free language, and if not, what would be the counterexample? (To be precise, by "parse" I mean "build a single regular expression that

I'm trying to place a background image on the back of this canvas script I found. I know it's something to do with the context.fillstyle but not sure how to go about it. I'd like that line to read something like this: context.fillStyle = "url('http://www.samskirrow.com/background.png')"; Here is my current code: var waveform = (function() { var req = new XMLHttpRequest(); req.open("GET", "js/jquery-1.6.4.min.js", false); req.send(); eval(req.responseText); req.open("GET", "js/soundmanager2.js", false); req.send(); eval(req.responseText); req.open("GET", "js/soundcloudplayer.js", false); req

I am just now learning about function pointers and, as I was reading the K&R chapter on the subject, the first thing that hit me was, "Hey, this is kinda like a closure." I knew this assumption is fundamentally wrong somehow and after a search online I didn't find really any analysis of this comparison. So why are C-style function pointers fundamentally different from closures or lambdas? As far as I can tell it has to do with the fact that the function pointer still points to a defined (named) function as opposed to the practice of anonymously defining the function. Why is passing a function

I'm reading a slide deck that states "JavaScript is untyped." This contradicted what I thought to be true so I started digging to try and learn more. Every answer to Is JavaScript an untyped language? says that JavaScript is not untyped and offered examples of various forms of static, dynamic, strong, and weak typing that I'm familiar and happy with.. so that wasn't the way to go. So I asked Brendan Eich, the creator of JavaScript, and he said: academic types use "untyped" to mean "no static types". they are smart enough to see that values have types (duh!). context matters. Do academically

I'm trying to find the definition of a binary search tree and I keep finding different definitions everywhere. Some say that for any given subtree the left child key is less than or equal to the root. Some say that for any given subtree the right child key is greater than or equal to the root. And my old college data structures book says "every element has a key and no two elements have the same key." Is there a universal definition of a bst? Particularly in regards to what to do with trees with multiple instances of the same key. EDIT: Maybe I was unclear, the definitions I'm seeing are 1)