Here's a curious program fragment: object obj = "Int32"; string str1 = "Int32"; string str2 = typeof(int).Name; Console.WriteLine(obj == str1); // true Console.WriteLine(str1 == str2); // true Console.WriteLine(obj == str2); // false !? Surely if A equals B, and B equals C, then A equals C; that...

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(Note: not to be confused with Inheritance and Representation .) I get a fair number of questions about the C# cast operator. The most frequent question I get is: short sss = 123; object ooo = sss; // Box the short. int iii = (int) sss; // Perfectly legal. int jjj = (int) (short) ooo; // Perfectly...

As I have said before many times , there is only one sensible way to make a performant application. (As an aside: perfectly good word, performant, deal with it!) That is: Set meaningful, measurable, customer-focused goals. Write the code to be as clear and correct as possible. Carefully measure your...

The other day my charming wife Leah and I were playing Scrabble Brand Crossword Game (a registered trademark of Hasbro and Mattel) as is our wont. I went first, drawing the Q and a bunch of vowels. Knowing that the Q is death to hold onto, I immediately opened with QI for 22 points. I silently thanked...

I got a moral question from an author of programming language textbooks the other day requesting my opinions on whether or not beginner programmers should be taught how to use arrays. Rather than actually answer that question, I gave him a long list of my opinions about arrays, how I use arrays, how...

OK, computers aren't entirely dumb when it comes to LINQ. Here's an example of a place where we're a bit smarter. Consider the following query: IEnumerable<int> query = from n in number_array orderby n select n; Does this get transformed by the compiler into IEnumerable<int> query...

A few short takes today, from questions I've received recently about LINQ in C# 3.0. The first question was " in the following code, does it really check every single non-negative integer, or does it use the knowledge that once you're beyond ten, you can stop iterating? " var smallNumbers = Enumerable...

Last time I demonstrated that the compiler could have to do an exponential number of bindings in order to determine whether there was a unique best overload resolution for a function call that takes a lambda. Some of you may have wondered whether we simply were not being clever enough in the compiler...

Hey all, sorry for the long time between posts; I have been crazy busy recruiting , interviewing, fixing bugs, making performance improvements and implementing last-minute changes to the language and expression tree library. The last few posts about lambda binding yielded many interesting comments which...

I just got a question this morning about how to take two collections of items and determine how many of those items had the same name. The user had written this straightforward but extremely slow VBScript algorithm: For Each Frog In Frogs For Each Toad In Toads If Frog.Name = Toad.Name Then SameName...

About two years ago I wrote a bit about when it was legal to cache a dispatch identifier so that you didn’t have to look it up a second time . I was reminded of this today because the scripting sustaining engineering team was working on a bug that involved a customer incorrectly caching a dispatch identifier...

We’ve got a system that meets all our needs for disambiguating hierarchical constants through partial or full qualification. (In the event of a collision between an enumerated type name and a value in a given library, the type name wins so that full qualification can work.) But what about the performance...

Script developers can declare constants, variables, functions and classes at global scope by writing the appropriate lines of code. Script hosts (Internet Explorer, ASP, WSH, etc) however can only add objects to the script engine’s global scope. For practical purposes, it’s as though the host creates...

(Sorry about the title. I work for Microsoft; we like nouns .) Over a year ago now a reader noted in a comment to this posting that defining named constants using Const in VBScript or var in JScript is way, way faster than importing a type library. My empirical JScript testing showed that loading...

All of this stuff about high dimensional geometry has been known for quite a while. The novel bit that this paper is all about is how to actually build a fast index for searching a high-dimensional space where the query has a strong likelihood of being junk . The idea that these smart Microsoft researchers...

It's reasonably common to have a database containing a few thousand or million points in some high-dimensional space. If you have some "query point" in that space you might like to know whether there is a match in your database. If you're looking for an exact match then the problem is pretty easy --...

My next book project is ready for copyediting, the wedding invitations are sent out, my bug count is under control, I've got a layer of levelling compound poured in the basement, there's no more ivy on my roof, and I’m rigging my sailboat some time this week (about six weeks later than I would have liked...

The volume of an n-cube of edge length s is easy to work out. A 2-cube has s 2 units of area. A 3-cube has s 3 units of volume. A 4-cube has s 4 units of 4-volume, and so on -- an n-cube has s n units of n-volume. If the n-cube has edge of s>1, say s=2, then clearly the n-volume dramatically increases...

A friend of mine over in Microsoft Research pointed out to me the other day that high-dimensional spaces are really counterintuitive. He'd just attended a lecture by the research guys who wrote this excellent paper and we were geeking out at a party about it. I found this paper quite eye-opening and...

Here's a question about client side vs. server side scripting that I got recently: I want to get the machine name of the client the request is being made from. With ASP I can get the IP address using this code: ipaddr = Request.ServerVariables("REMOTE_ADDR") But I don’t know how to get the name of...

So, how many files are we talking about here? I've got over thirty thousand source code files containing over seven million unique words. There are pretty much two kinds of words -- words that occur in one, two, a dozen files, and words that occur in almost every file. ("Microsoft", "next", etc.) An...

Before I get started with my next series, two quick notes. First, at long last I had dinner with famed JOS poster (and east coast technical evangelist for my product, VSTO) Philo the other night, as he happened to be in Redmond. I'm pleased to report that he's as witty, urbane and opinionated in real...

Q: What's a pirate's second favourite mode of transportation? A: A caaaaargh! Preferably a Jaguaaaaargh, but an early Oldsmobile Cutlass will do. Q: Very amusing -- but what's a pirate's favourite mode of transportation? A: A pirate ship, silly. Gripe #10: Don't use _alloca _alloca allocates...

Back in May we were discussing the merits and drawbacks of recursive programming techniques -- that is, writing functions which break down problems into sub-problems, and then call themselves. The drawback of such an approach is that in some cases, you end up doing way more work than necessary...