My brother Sam was visiting recently and corrected me when I used the word "data" as a collective singular rather than the plural. He made some huffy comment about the difference being important to scientists. Back to that in a moment.
A few days ago I discovered that professional wrestling was older than I thought while watching a film from the 1940's. Well today I discovered that the use of data as a singular noun dates from at least that far back as well. This time my source is "The Philadelphia Story," also filmed in the 1940's. Jimmy Stewart, playing an author working as a journalist, says, "Our research department didn't give us much data."
I was about to send a snide note to Sam, when I started to wonder about the 'data' statement in Haskell, used to construct new types. There is also a 'type' statement and a 'newtype', both apparently singular, but then, each constructs exactly one type. So I have to wonder, is "data" in this context also singular?
If Haskell used "datum" instead, and there was more than one element in the type, it wouldn't make sense, I suppose. Of course, no sane language designer would force you to use 'datum Singular = One', but 'data Plural = One | Two', would he? Details like that are important in the semantics of Haskell, though perhaps not the syntax. Still, perhaps I should be more careful about my usage.