I said something about Perl 6 the other day, and someone replied asking whether anyone actually uses Perl 6. My first thought was I bet more people use Perl 6 than Haskell, and it’s well known that people use Haskell. I looked at the TIOBE Index to see whether that’s true. I won’t argue how well the index measures popularity, but for this post I’ll assume it’s a good enough proxy.
TIOBE doesn’t separate out variations on Perl . What it calls Perl is 16th on the list this year, while Haskell comes in at 42nd. A few of the more obscure languages that TIOBE ranks higher than Haskell are Scratch, D, ABAP, Apex, and PL/I. Haskell has better public relations than all these languages.
There’s a lot more to viability than just popularity, though popularity matters. More users means more people to find bugs, write libraries, develop tools, answer questions, write tutorials, etc. But the benefit of community size is not linear. It goes through a sort of logistic S-curve. There’s some threshold size where the community is large enough for a language to be viable. And somewhere above that threshold you start hitting diminishing return.
It’s interesting to look at some of the languages currently less popular than Haskell but more familiar: Common Lisp (63), Erlang (66), and F# (67). These show that popularity isn’t everything.
Common Lisp has been around since 1982, and standardized a language that had been in development since 1958. Erlang has been around since 1986. These languages have many of the benefits of popularity listed above, accumulated over time.
There is not a huge community devoted specifically to F#, but it shares tooling and libraries with C#, the 5th language on the list. (Maybe the number of F# developers is underestimated because F# is so closely related to C#, not syntactically but in terms of infrastructure.)
Common Lisp, Erlang, and F# would all be safer bets for a production software project than several more popular languages.
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 At least I don’t think they do. TIOBE does separate out some versions of Lisp as separate languages. It’s possible they do consider Perl 6 a separate language that didn’t make the top rankings.
Larry Wall deliberately introduced many natural language principles in Perl. It seems that one feature that Perl has in common with natural languages is controversy over when two dialects of a language are sufficiently different to be considered separate languages. Advocates consider Perl 6 to be a separate language but outside observers, like TIOBE, may not.