Advent of Code 2020 in Common Lisp

I'm using the Advent of Code 2020 to exercise my Common Lisp muscles.

https://adventofcode.com/2020

Learnings

Common Lisp is an enormous language with a rich library ecosystem. It's easy to get stuck in the same old corner of the language you are familiar with. What I love about the Advent of Code event is the opportunity to see how other hackers tackle the same small problems. Here are some of my personal learnings from 2020.

• labels is like flet but allows for recursion
• Check that a value is within a range thusly: (<= min value max)
• You can map any sequences, for example (map 'string #'fn "ssdfs")
• cl-ppcre:register-groups-bind simplifies text extraction
• parseq can be an even nicer text parsing tool
• alexandria:xor is Common Lisp's missing xor
• metabang-bind can simplify code that requires multiple different kinds of bindings
• alexandria:map-combinations and related functions are nice

Anthony Green green@moxielogic.com