Weasel Program - Example Algorithm

Example Algorithm

Although Dawkins did not provide the source code for his program, a "Weasel" style algorithm could run as follows.

1. Start with a random string of 28 characters.
2. Make 100 copies of this string, with a 5% chance per character of that character being replaced with a random character.
3. Compare each new string with the target "METHINKS IT IS LIKE A WEASEL", and give each a score (the number of letters in the string that are correct and in the correct position).
4. If any of the new strings has a perfect score (28), halt.
5. Otherwise, take the highest scoring string, and go to step 2.

For these purposes, a "character" is any uppercase letter, or a space. The number of copies per generation, and the chance of mutation per letter are not specified in Dawkins's book; 100 copies and a 5% mutation rate are examples. Correct letters are not "locked". Each correct letter may become incorrect in subsequent generations. The terms of the program and the existence of the target phrase do however mean that such 'negative mutations' will quickly be 'corrected'.