cl-problem-solving

Hobby project using Common Lisp to solve numeric puzzles as those proposed by Project Euler.

When relevant, an optimized solution, compiling with no note under (speed 3) is proposed.

A test suite is proposed.

Table of contents:

• Usage
• Project Euler
• Other puzzles
• Tupper formula
• License

Any comment? Open an issue, or start a discussion here or at profile level.

Usage

Register the project with ASDF, from the REPL or once and for all in your .sbclrc:

(push #P"c:/.../cl-problem-solving/" asdf:*central-registry*)

Then load it and solve everything at once:

(asdf:load-system :cl-problem-solving)
(cl-problem-solving:main)

Each problem is exported individually. Where a plainer version is kept beside the optimized one, its name carries a -- suffix saying what it is:

(cl-problem-solving:project-euler-001)                 ; => 233168
(cl-problem-solving:project-euler-001--not-optimized)  ; same answer, plainer code
(cl-problem-solving:project-euler-001 10)              ; => 23

To run the test suite:

(asdf:test-system :cl-problem-solving)
(parachute:test :cl-problem-solving-tests)             ; same, directly

Project Euler

Project Euler problems solved are: 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 80, 81, 89, 254, 684.

Other puzzles

• Anecdotes Maths — Mathematical anecdotes and curiosities from @AnecdotesMaths
• Certificat — Josephus problem
• Devil Calculator — Devil Math Facts
• Fermat's Library — Number theory curiosities from @fermatslibrary
• Ile Maths — French number-to-words conversion

Tupper formula

Blog post: https://www.effectivelambda.org/en/blog/006-tuppers-self-referential-formula.html

Tupper's self-referential formula is a formula that visually represents itself when graphed on plane.

See Wikipedia or Wolfram MathWorld.

Formula:

SBCL supports 'big' integers, which allows implementing the formula directly:

Output:

I have added this code to Rosetta Code.

License

Copyright (c) 2025 Nicolas Occis

Licensed under the MIT License.

(end of README)