ProjectEuler-J

Solutions to Project Euler problems using the J programming language.

Synopsis

The scripts in this project solve the corresponding problems provided at projecteuler.net while using the fewest number of characters as possible. The only time that the efficiency of a script takes priority over its length is when the more terse solution takes an inexcusably longer amount of time to finish running (e.g. 5 minutes vs 5 seconds).

Examples

Solution Priority

It is possible to find the 100001^st prime number with both the following scripts:

1. p:100001
2. p:>:1e5

While the first script is simpler, and probably marginally more efficient, it is not the solution that would be used in this project. As far as this project is concerned, the second script is superior because it contains fewer characters.

Solution Comments

Because terseness is one of this project's highest priorities, unnecessary white-space is never implemented in any of its scripts. This can make them difficult to read. To compensate for this, each script will end with a commented section containing an indented process tree.

A typical script will look something like this:

0-((1-2)-3-4)-5

NB. 5             5
NB. )-            Subtracted from
NB.     4             4
NB.     3-            Subtracted from 3
NB.     )-            Subtracted from
NB.         2             2
NB.         1-            Subtracted from 1
NB.     (         
NB. (             
NB. 0-            Subtracted from 0

A tree follows its script from top to bottom. Subprocesses are indicated by increased indentation, and must finish executing before the parent process can return a value.

File Names

Solutions

Solutions are stored in files named in "problemddd.ijs" format.

e.g. The solution to problem 3 is stored in problem003.ijs

Efficient Solutions

If a terse solution takes significantly longer than a more efficient solution, the efficient solution will be stored in a file named in "problemddd.eff.ijs" format.

e.g. The efficient solution to problem 4 is stored in problem004.eff.ijs

Input

If a problem uses input that is longer than a single short line of charcters, the input will be stored in a file named in "problemddd.txt" format.

e.g. The input for problem 13 is stored in problem013.txt

ProjectEuler-J Library

pej_help

Within the project is a file named pej.ijs that defines several useful verbs. Once pej.ijs is loaded, pej_help 'all' will print a list of all the verbs defined by pej.ijs, and pej_help 'pej_verb' will print a description of pej_verb and examples of how to use it.

Loading pej.ijs

From within the ProjectEuler-J directory:

From terminal: launch the J interpreter with the parameter pej.ijs

OR

From the J interpreter: run load 'pej.ijs'