Initially, I had written hackage-fetch to see if there was any use of coelgot anywhere on Hackage. At the time, there was not, but this has changed due to my gmpint package. As of writing, it is not surprisingly the only use of co-(Elgot algebra)s on the entirety of Hackage.

And Hackage is big! It's 12626 packages as of writing, totaling 37 million lines of code, 21.5 million of which are Haskell. You can see the table produced by polyglot below:

------------------------------------------------------------------------------- Language Files Lines Code Comments Blanks ------------------------------------------------------------------------------- Alex 200 35645 28248 2370 5027 Agda 30 1542 1166 44 332 Assembly 42 33366 33065 0 301 ATS 34 4639 3973 305 361 Autoconf 359 112331 109199 0 3132 Automake 13 795 667 0 128 Bash 1081 47132 40230 0 6902 Batch 29 680 626 0 54 Brainfuck 5 16 16 0 0 C 4505 3318644 2953890 28369 336385 C-- 9 2011 1625 15 371 C++ 1950 1990678 1796681 58107 135890 C Header 5805 1981250 1841160 0 140090 Cabal 13890 926906 832160 20838 73908 Cabal Project 112 335 315 8 12 Cassius 47 1679 1390 0 289 Coq 11 5384 5102 0 282 CSS 643 128135 118444 0 9691 Dhall 429 3060 2972 0 88 Elm 60 6453 6344 25 84 Emacs Lisp 71 25930 22745 0 3185 Erlang 1 11 8 0 3 FLTK Data 12 3150 3140 0 10 Fortran 27 4815 4290 0 525 Go 29 589 504 3 82 Greencard 4 455 255 96 104 Hamlet 168 4162 4081 0 81 Happy 150 72173 55796 4757 11620 Haskell 137811 21552185 16268284 2497001 2786900 HTML 1235 218891 205478 0 13413 Idris 621 37050 28754 1170 7126 iPKG 29 401 288 2 111 Java 354 50846 44730 466 5650 JavaScript 2164 1255619 1126360 6142 123117 Julius 25 1139 1042 0 97 Jupyter 3 756 756 0 0 Lex 111 380 376 0 4 LLVM 32 3368 2793 0 575 Lua 73 16874 13080 1115 2679 M4 57 5451 4567 0 884 Madlang 19 401 380 0 21 Makefile 639 27039 21387 0 5652 Markdown 7021 407296 295252 0 112044 Nix 32 23896 19527 0 4369 Objective C 31 11247 9524 0 1723 OCaml 1 9 7 0 2 Perl 29 12537 11693 0 844 PHP 6 1610 1474 0 136 Plaintext 1873 4499766 4437368 0 62398 PowerShell 6 471 384 0 87 Python 103 27920 25817 0 2103 PureScript 624 8357 6218 0 2139 R 20 1340 1197 0 143 Ruby 9 339 295 0 44 Rust 1 12 3 5 4 Scala 2 100 78 0 22 Swift 7 630 592 0 38 TCL 5 1109 892 0 217 TeX 1528 49390 43637 0 5753 TOML 163 1497 1219 0 278 VHDL 4 943 821 0 122 Vimscript 84 5118 4703 0 415 YAML 4252 405772 371414 0 34358 ------------------------------------------------------------------------------- Total 188665 37336109 30813462 2620727 3901920 -------------------------------------------------------------------------------

So there's a lot of different stuff on Hackage. Some of that is unsurprising (Elm, PureScript, Dhall, Agda, and Idris are implemented in Haskell), but some of it is more off-beat (VHDL, Coq, ATS).

C is the second-most popular language, with 3.3 million lines of C on Hackage. This is somewhat surprising - it is one seventh as common as Haskell! Perhaps due to its prolixity, but nonetheless striking.

That's our brief tour of the ecosystem. Hopefully it manages to impress upon you the scale of extant Haskell, as well as some of the cross-pollination happening with other ecosystems.