Jeremy W. Sherman
This year's language is: Mercury, which is like a statically-typed Prolog with a focus on fast execution.
This year's challenges can be found at: https://adventofcode.com/2020
mmc drops a lot of stuff in the current directory unless you pass --use-subdirs, so you'll want to:
# fish syntax
cd build/
set -x DAY 1
mmc --use-subdirs ../src/day$DAY.m && ./day$DAY < ../input/day$DAY.txt
There's probably some clever way to automate this with Make, but, meh.
> mmc --version
Mercury Compiler, version 20.06, on x86_64-apple-darwin19.6.0
Copyright (C) 1993-2012 The University of Melbourne
Copyright (C) 2013-2020 The Mercury team
> sw_vers
ProductName: Mac OS X
ProductVersion: 10.15.7
BuildVersion: 19H15