Playing with language: Inlined fromMaybe
Date : 2008 03 03 Category : Tech & Development
AjaxianOliver Steele continues to spend time thinking about languages in his recent post on More Monads on the Cheap: Inlined fromMaybe.
He details the pain of dealing with nulls and various checks:
This article is about how to deal with null values. It follows up on this one. It’s intended for code stylists: people who care a lot about the difference between one line of code and two, or keeping control statements and temporary variables to a minimum. (A code stylist is kind of like the dual of a software architect, although one person can be both.) It’s not about code golf — although you might learn some strokes to use on that — but about keeping the structure of your code, even at the expression level, close to the way you think about the problem, if you think like me.
If you’re not a code stylist — and I’m not saying that being a code stylist, any more than being a prose stylist, is either a good or a bad thing — you might find it baffling that someone would put so much time into such simple topic. I won’t try to convince you otherwise. In that case, you might want to check back next week, when I’ll move back up to the bigger picture. (Specifically, some fun stuff involving how to use meta-object programming to solve race conditions in client-server models.)
He ends up with an inline fromMaybe solution:
To change code that expects a non-nullable array to a nullable array, change array to array||[]. This is a local transformation: it changes an expression into an expression (not a statement), so you don’t need to re-write the code that contains it. It’s also a linear transformation (again, in the sense of linear logic, not linear algebra): an expression that only occurs once before the transformation, only occurs once after it.
PLAIN TEXT JAVASCRIPT:var count = (products || []).length;
var value = parseInt(inputString || ‘0’, 10);
var option = ({key:‘default’}.key;
var result = (fn || Function.K(defaultValue))(argument);
sprite.moveTo(x || 0, y || 0);