https://github.com/tommay/sudoku-in-erlang

Thrashing in Erlang and learning a lot.
https://github.com/tommay/sudoku-in-erlang

Last synced: about 6 hours ago
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Thrashing in Erlang and learning a lot.

• Host: GitHub
• URL: https://github.com/tommay/sudoku-in-erlang
• Owner: tommay
• License: mit
• Created: 2015-02-14T05:09:59.000Z (almost 10 years ago)
• Default Branch: master
• Last Pushed: 2016-10-15T00:54:10.000Z (about 8 years ago)
• Last Synced: 2023-04-19T16:52:49.960Z (over 1 year ago)
• Language: Erlang
• Size: 86.9 KB
• Stars: 0
• Watchers: 2
• Forks: 0
• Open Issues: 0
• Metadata Files:
  • Readme: README.md
  • License: LICENSE.md

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README

        
sudoku

======

A little sudoku solver in Erlang.  This is sort of a port of my

[sudoku solver](https://github.com/tommay/sudoku) done in various

other languages (Ruby, JavaScript, CoffeeScript) but Erlang is a

different beast entirely even for a Lisp hacker.  I've been learning a

lot about how to do functional programming somewhat cleanly in Erlang

with a module per "object", tagged values, etc.  Functional

programming seems to demand a "tell, don't ask" style and violating

the law of Demeter is right out.  So it should be a good influence on

my designs in other languages.  At least I've been a fan of

immutability for decades

This finally works!  I made an escript executable that takes a filename

and prints any solutions.

I've gotten quite comfortable with the pattern matching and like it a

lot.  If we get this, do that.  If we get something else, do the other

thing.  Give this piece of the arguments a name so we can use it

later.

It's not clear whether I'll be sticking with some of my design

approaches.  It's also strictly functional with no actors or

concurrency.  I'll play with those later, probably when I add

statistics of the various techniques.

Update: I wanted multiple processes when solving puzzles with multiple

solutions so I could use all available cores.  But that made an

overwhelming number of processes for Erlang to deal with and it would

run out of memory and crash.  So now there is a limiter process which

tracks the number of spawned processes and doesn't allow more than N

to run at once.  There is also a stats server process.

Somtimes it still feels weird to be writing functions that "don't do

anything"; they just look at their arguments and return some new junk,

often a slightly modified copy of itself.  It's like telling a dog to

walk across the room, but instead of actually walking across the room

it creates a new dog that's on the other side of the room and you use

that dog instead.  And you still have the old dog on your side of the

room, until you ignore it long enough and the garbage collector cleans

it up.