For example, I wrote a compact disc bookkeeping system (heavy on parsing text files) when I learned Perl; I learned Ruby and Rails by writing an auction site; I learned Fortran by writing a nonlinear least-squares fitter; I learned Erlang by writing a chat server...

The list goes on, but you get the picture. Pick a language based on its being the right tool for a particular job, then do that job. :)

Do you have any that play at all? How strong are they typically? curious.

-Paul

None of them actually play cause I suck at implementing the alphabeta algorithm. Though, the one I'm working on in JS right now will do so because I think I've figured out a way of short-circuiting the alphabeta so that only the best positions are evaluated first.

---

My criteria for good software:

1. Does it work?
2. Can someone else come in, make a change, and be reasonably certain no bugs were introduced?

This likewise has the benefit of being expandable to include some simple input, whether it be on the command line or otherwise.

Here's what it would look like if I were writing it in Perl...

#!/usr/bin/perl

use strict;
use warnings;

my $number = 1;
my $limit = 20;

my @list_of_nums;

while ($number < $limit) {
  push @list_of_nums, $number;
  $number = $number + $list_of_nums[-2];
}

foreach my $item (@list_of_nums) {
  if (odd($item) eq 'Odd') {
    print "$item is Odd\n";
  }

  else {
    print "$item is Even\n";
  }
  
}


sub even {
  my $num = shift @_;

  if ($num == 1)
    {
      return 'Even';
    }

  else
    {
      return odd(--$num);
    }
}

sub odd {
  my $num = shift @_;

  if ($num == 1)
    {
      return 'Odd';
    }

  else {
    return even(--$num);
  }
}
[download]

Usually, I choose to learn a new language when I have a project for which that language would be especially good. So, I write something completely new.

I did this in Pugs to try out Perl 6 and liked it so much I wrote an article about it. But, I've done it for many other languages over the years including Perl 5 and even (shudder) COBOL.

Phil

I then write a Fibonacci generator as close to this recursive formula as possible (ignoring the fact that there are better ways to do it):

use strict;

for my $i (0 .. 35) {
    print "i=$i ... fib(i)=", fib($i), "\n";
}

sub fib {
    my $n = shift;

    return fib($n-1) + fib($n-2) if $n>1;
    return 1;
}
[download]

My favorite "first program" to write in a language is the Knight's Tour. My reasons are basically that it's easy to implement and since I don't often learn more than one language a year, it also helps me keep track of how much faster computers are getting. (I make the board size a parameter, and have it keep solving larger and larger boards until I'm bored watching it.)

Once I've written it, I look around and see if I can make it more idiomatic for the language. (Why write in the C subset of a language? If that's what you want, just use C.) Some languages offer the opportunity to use a different data structure for the board or other implementation strategies. After I get it running nicely, I try to see if I can code up new heuristics to chop off subtrees. It's often a fun way to spend a day when you need to relax.

I don't know exactly how many versions I've written, but it's likely between 25 and 35. (Not counting the hacking sessions of optimizing and idiomizing, etc. If I were to count those, it could possibly be well over 500.)

I just realized something ... I've never done it in perl. If I weren't at work right now, I'd do that. As it stands, I think I'll do it this evening and post it tonight or tomorrow.

It has indeed been very useful for learning new languages for me... I can start with what's common with a language I already know, and incrementally add features and techniques as I learn them. And it lets me concentrate on the language, instead of solving a new problem. Which would be the next step.

Here's a site that shows it working: http://sas-crash.homelinux.net/sas/cgi-bin/logon9c.pl. Bug reports are welcome.

Update: fixed the link.. I swear it was good when I put it in.

I start with "Hello World" then cut to the chase with what I need to do with the program. Useless politeness?

I program because I have problems. (No, not that kind of problems.) There is some task I can make the computer do for me, so I start programming. Picking the programming language comes after having a problem to solve. Most often it's Perl, since it's a pragmatic programming language and available on most computers I have access to (including in particular $work). Sometimes I pick C if I need better access to hardware or libraries or manual memory control. Sometimes I pick $functional_language[rand @functional_language] because the solution may be more easily expressed in it. Sometimes the environment the program must execute in limits the choice (e.g. Javascript).

Of course, this kind of an approach presupposes that you know the programming language very well, or at least are familiar with a wide range of different concepts.

When I was still taking first steps into programming in Pascal and C, I used to write a program that queries the user for a radius, then prints the circumference and area of a circle or sphere. But that was a decade ago.

I mean no offence, but "learning how to write a subroutine or function" in a new programming language sounds silly. It's a matter of syntax, if the programming language has some form of functions or goto. (If it doesn't, this is an interesting problem, but it was already solved in 1950s.) It's much more worth your while to learn a new concept through exposure to a new programming language.