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• As Timeless As Infinity

  User: Recently I found out about a peculiar behaviour concerning division by zero in floating point numbers in C#. It does not throw an exception, as with integer division, but rather returns an "infinity". Why is that? Eric: As I've often said, "why" Read More... Posted Thursday, October 15, 2009 6:25 AM by Eric Lippert | 32 Comments Filed under: VBScript, C#, Floating Point Arithmetic, Dialogue, Language Design, exception handling, Delphi

• Bug Psychology

  Fixing bugs is hard. For the purposes of this posting, I’m talking about those really “crisp” bugs -- those flaws which are entirely due to a failure on the developer’s part to correctly implement some mechanistic calculation or ensure some postcondition Read More... Posted Monday, June 01, 2009 6:48 AM by Eric Lippert | 28 Comments Filed under: VBScript, Scripting, Rants, Interviewing

• Reading Code Over the Telephone

  In my youth I once attended a lecture given by Brian Kernighan on the subject of code quality, which was very influential on my attitudes towards writing legible code. One of the things that Kernighan recommended was to endeavour write code that was so Read More... Posted Friday, May 16, 2008 7:00 AM by Eric Lippert | 25 Comments Filed under: VBScript, C#, Lambda Expressions, Code Quality

• Do Not Call IsBadFooPtr, Indeed

  Here’s a story that I said a long time ago that I was going to tell you all , and then promptly forgot about it. Raymond Chen’s blog entry today reminded me of it, because this is the story of how I found out the hard way that IsBadFooPtr is bad, bad, Read More... Posted Wednesday, September 27, 2006 11:16 AM by Eric Lippert | 11 Comments Filed under: VBScript, COM Programming

• Checking For Script Syntax Errors, This Time With Code

  A number of people asked me to clarify yesterday's entry. Rather than try to talk you through it, I think the code is straightforward enough to speak for itself. Here's a little skeleton that I just whipped up. #include <stdio.h> #include <activscp.h> Read More... Posted Wednesday, October 12, 2005 9:37 AM by Eric Lippert | 9 Comments Filed under: JScript, VBScript, Scripting, COM Programming

• Checking For Script Syntax Errors

  A reader asked me recently whether there was a way to check a chunk of JScript or VBScript for syntax errors without actually running the code. I'm sure that there are many third-party tools which you could find that do this. If you have your own script Read More... Posted Tuesday, October 11, 2005 10:35 AM by Eric Lippert | 8 Comments Filed under: JScript, VBScript, Scripting

• Implementing Event Handling, Part Two

  It's been an insanely busy month for me, between having multiple out-of-town guests, throwing a party for the people who couldn't make it to the wedding, and oh yeah, getting up to speed on the C# compiler and trying to understand the implications that Read More... Posted Wednesday, September 21, 2005 11:51 AM by Eric Lippert | 3 Comments Filed under: JScript, VBScript, Scripting, COM Programming

• 250% of what, exactly?

  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 Read More... Posted Thursday, September 01, 2005 10:13 AM by Eric Lippert | 27 Comments Filed under: VBScript, Scripting, Performance

• VBScript Default Property Semantics

  Here’s a question I recently got about VBScript, where by "recently" I mean August 28th, 2003. This code works just fine: Set myObject = CreateObject("myObject") myObject.myName = "Eric" WScript.Echo myObject ' myName is the default property, so prints Read More... Posted Tuesday, August 30, 2005 10:15 AM by Eric Lippert | 10 Comments Filed under: VBScript, Scripting, COM Programming

• Scripting Type Library Constant Injection Performance Characteristics, Part One

  (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 Read More... Posted Wednesday, June 22, 2005 8:00 AM by Eric Lippert | 1 Comments Filed under: JScript, VBScript, Scripting, Performance

• Bad Recursion Revisited

  We have internal email lists for questions about programming languages. Here's one that came across recently that I thought illustrated a good point about language design. An interview candidate gave the following awful implementation of the factorial Read More... Posted Thursday, April 28, 2005 12:12 PM by Eric Lippert | 22 Comments Filed under: JScript, VBScript, Scripting, C#, Code Quality, Recursion, precedence

• How Do Script Engines Implement Object Identity?

  I've talked a few times in this blog about the semantics of the equality operators in various languages. (Such as here , and here .) Recently a reader asked me how JScript implements object identity. That is, given two objects, how do we know if they Read More... Posted Tuesday, April 26, 2005 12:49 PM by Eric Lippert | 7 Comments Filed under: JScript, VBScript, Scripting, COM Programming

• Binary Files and the File System Object Do Not Mix

  OK, back to scripting today. But before I get back to scripting issues, one brief correction. An attentive reader noted that "The Well-Tempered Clavier" was in fact designed to sound good on a "well tempered" instrument, not an "equally tempered" instrument. Read More... Posted Wednesday, April 20, 2005 12:47 PM by Eric Lippert | 31 Comments Filed under: VBScript, Scripting, Code Quality

• VBScript Quiz Answers, Parts Eleven and Twelve

  11) X and Y are both Booleans. Which of the following always assigns True ? Why? (a) Z = Not X Or Y = X Imp Y (b) Z = X Imp Y = Not X Or Y (c) Z = X Eqv Y = Not X XOr Y (d) Z = Not X XOr Y = X Eqv Y (a) assigns False if X and Y are both False . The others Read More... Posted Tuesday, April 05, 2005 12:25 PM by Eric Lippert | 7 Comments Filed under: VBScript, Scripting, Puzzles

• VBScript Quiz Answers, Parts Nine and Ten

  9) Which of these statements is syntactically legal? Why? (a) Const Z = -+-+-+-10 (b) Const Y = 2 + 2 (c) Const X = .1e310 (d) Dim W(+10) (a) is legal. The rest are illegal. (a) is legal because you can put as many unary positive or negative operators Read More... Posted Wednesday, March 30, 2005 10:25 AM by Eric Lippert | 7 Comments Filed under: VBScript, Scripting, Puzzles