Autojudge "Golfing language extensions"

A code golf challenge decribed in this post by Taylor Fausak drowned some people into madness.

Manually judging answers for the challenge was so tiresome and error-prone. This program automates it.

Requirement

• GHC 8.10.* is installed and can invoke its compiler by command ghc.
• cabal-install is set up.

How to compile

cabal build judge

How to run

1. Prepare
   • Haskell program to be tested (a.hs)
   • A file listing name of GHC language extensions (extensions.txt) each separated by whitespace characters
2. cabal run -- judge a.hs --exts extensions.txt

How to read outputs

$ cabal run -- judge original.hs --exts extensions.txt
Up to date
PASSED
  Score(chars/exts):3.5238095238095237
=================================
SourceStat {srcLenCodepoints = 74, srcLenUtf8Bytes = 84}
exts=21=21+0

• PASSED -- Input is valid. The program compiles with given list of extensions, and removing any one of extension make it fail to compile. If the input was invalid, FAILED is printed out.

• Score(chars/exts): -- How good the input is. Measured by how many characters (in Unicode codepoints) are in the program, divided by how many extensions required.

• SourceStat{..} -- Exists for the time when you want to measure by bytes

• exts=N=E+I -- Some extensions imply other extensions.

  If an extension E implies another extension I, enabling E also enables I. This can be overridden by specifying NoI. It was not clear how to score:

  • One requires E but don't require I to be enabled
  • One requires both E and I to be enabled

  This judge program don't allow former to advertize "require 2 extensions", but allow for latter. When seeing both E and I in the extensions list file, the judge counts them as 2 extensions, and rejects the former program.

  The output exts=N=E+I means the judge recognizes N extensions total, including I extensions implied by other extensions listed and E extensions no other extensions imply it.

Sample inputs

• original.hs, extensions.txt: One presented in the blog post
• isovector.hs, extensions_isovector.txt: Current best, From comments on reddit

Caveat

This program does not test the case 2 or more extensions are omitted simultaneously.