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After deleting a web server, I started checking what I typed before hitting 'Enter'

The Register
1 month 3 weeks ago
Student thought she had the hang of this 'Linux' thing and its kooky CLI

Who, Me?  It's Monday morning, and a week of possibilities presents itself to IT pros everywhere. Which is why The Register brings you another edition of Who, Me? It's the reader-contributed column in which we remind you what not to do with your day, your week, and your career, by sharing stories of your worst workplace mistakes and the contortions you made to survive them.…

Simon Sharwood

CodeSOD: Functionally, a Date

The Daily WTF
1 month 3 weeks ago

Dates are messy things, full of complicated edge cases and surprising ways for our assumptions to fail. They lack the pure mathematical beauty of other data types, like integers. But that absence doesn't mean we can't apply the beautiful, concise, and simple tools of functional programming to handling dates.

I mean, you or I could. J Banana's co-worker seems to struggle a bit with it.

/** * compare two dates, rounding them to the day */ private static int compareDates( LocalDateTime date1, LocalDateTime date2 ) { List<BiFunction<LocalDateTime,LocalDateTime,Integer>> criterias = Arrays.asList( (d1,d2) -> d1.getYear() - d2.getYear(), (d1,d2) -> d1.getMonthValue() - d2.getMonthValue(), (d1,d2) -> d1.getDayOfMonth() - d2.getDayOfMonth() ); return criterias.stream() .map( f -> f.apply(date1, date2) ) .filter( r -> r != 0 ) .findFirst() .orElse( 0 ); }

This Java code creates a list containing three Java functions. Each function will take two dates and returns an integer. It then streams that list, applying each function in turn to a pair of dates. It then filters through the list of resulting integers for the first non-zero value, and failing that, returns just zero.

Why three functions? Well, because we have to check the year, the month, and the day. Obviously. The goal here is to return a negative value if date1 preceeds date2, zero if they're equal, and positive if date1 is later. And on this metric… it does work. That it works is what makes me hate it, honestly. This not only shouldn't work, but it should make the compiler so angry that the computer gets up and walks away until you've thought about what you've done.

Our submitter replaced all of this with a simple:

return date1.toLocalDate().compareTo( date2.toLocalDate() ); .comment { border; none; } [Advertisement] ProGet’s got you covered with security and access controls on your NuGet feeds. Learn more.
Remy Porter