When Rewriting an App Actually Makes Sense

vlangber writes "Joel Spolsky wrote a famous blog post back in 2000 called 'Things You Should Never Do, Part I,' where he wrote the following: '[T]he single worst strategic mistake that any software company can make: They decided to rewrite the code from scratch.' Here is a story about a software company that decided to rewrite their application from scratch, and their experiences from that process."

Comments

Re:Here's my short list

[Tanktalus]

Regarding regexes, I've gone both ways: I've had my developers remove regexes where they were trying to use them, and I've had them add regexes where they were trying too hard to avoid them. Regexes aren't the answer, they're a single tool. You need to use them right. And the /x modifier in Perl helps a lot, allowing you to put useful whitespace and comments in the code (and a regex is code as much as any other language).

As for "as few lines as possible" - you need to do it right. When you span your code over 3 pages, that's not readable anymore. I harp on this with my developers all the time: SCOPE. Scope applies to variables, comments, and functions. The less I need to look at to understand what you're doing, the more likely it is I'm going to understand it. A huge 3-page if-elseif-elseif-else is going to be something I'm not going to understand, as I'll have forgotten all the conditionals by the time I get to the end to know really what scenarios are left - sequential access. A concise regex, on the other hand, is something that I can skim over just by moving my eyes - random access. These concerns aren't just valid for storage media (tape vs DVD/HD). Of course, 40 characters of regex special characters with no whitespace (either horizontal or vertical, preferably both) is generally going to overwhelm most readers, and is going stupid in the other direction.

Yes, readability trumps length of code. But sometimes that means to use a regex (or two or three - why make one big cryptic one when multiple simpler regexes can do the job?). And sometimes, that means avoiding them when what you really want to do is better done by another piece of code.

My favourite new-to-regex example recently has been someone trying to pull apart colon-delimited text with a regex. Woops - there are better language constructs for tokenisation, whether that's strtok in C or it's split in Perl (or better, Text::CSV_XS). Got rid of that regex in a hurry.

Re:Here's my short list

[Surt]

You should think about investing in learning tools. Regex is a well documented, well understood, capable feature of all modern languages. How many weeks will you spend debugging / refining your thousands of if/then/else when you could trust years of testing that has been done on regex engines? Your statement reminds me of novices who avoid ?: in favor of if/else because it's 'cryptic'.