Pastable version of Experimental Prime Number Generator

<pre class='prettyprint' language='erlang'>-module(prime).
-export([main/0, print_if_prime/0]).

%
%   This function hasa prime factor that it uses to test numbers
%   as they are received.  Numbers that contain the prime factor
%   are simply dropped.  Other numbers are sent to the next child
%   in the chain.  If any of those child can reject the number as
%   not being prime, they do.  If none of them can, the number is declared 
%   to be prime and displayed.  A new child is added to the end of the list
%   to reject future numbers that have this as a prime factor.
%
%   EvilTeach, Aug 2008
%
print_if_prime() -&gt;
    
    receive
    
        % A quit message means shut down the whole chain
        {quit, _N} -&gt;

% Do we have a child?
            case ChildPid = get(child) of

% No, so we are the last child in the chain
                undefined -&gt; [];

% Yes, so we tell the next child to shutdown
                ChildPid -&gt; 
                   ChildPid ! {quit, 0}
            end,

% Erase my local dictionary 
            erase();

% Tell the subprocess which prime factor it is to service
        {you_check, N} -&gt;

io:format(&quot;~p IS PRIME~n&quot;,[N]),

put(myFactor, N),           
            print_if_prime();

% We need to check to see if N is prime
        {check, N} -&gt;

%io:format(&quot;~p check ~p against ~p~n&quot;, [self(), N, get(myFactor)]),

case N rem get(myFactor) of
                
                % a remainder of zero, indicates that is is not a prime
                0       -&gt; [];

% all other values need shipped off down the chain
                _Other  -&gt;

% Do we have a child to pass it to?
                    case ChildPid = get(child) of

% No. So we create one
                       undefined -&gt; 
                                         
                           % Create a child to check this new prime number
                           NewChildPid = spawn(fun prime:print_if_prime/0),

% io:format(&quot;Created PID ~p for ~p~n&quot;,[NewChildPid, N]),

% Save it so we can call it later
                           put(child, NewChildPid),

% Tell it which number it is responsible for checking N
                           NewChildPid ! {you_check, N};

% Yes, so we let the children deal with it
                       ChildPid -&gt; 
                           % io:format(&quot;We do have a child~n&quot;,[]),
                                           
                           % tell it to check this value
                           ChildPid ! {check, N}
                       end
            end,

print_if_prime()
    end.

generate_primes_from(N, Limit, _child) when N &gt; Limit -&gt; 
    % There are no more values to iterate through
    [];

generate_primes_from(N, Limit, FirstChild) -&gt;

%io:format(&quot;sending ~p~n&quot;,[N]),

% Tell the first child in the chain, to check the next number
    FirstChild ! {check, N},

% how every so often, we do a short delay to not overflow the message queue
    % 80 seems to be right for my machine for Limit =  10k
    % 20 seems to be right for my machine for Limit = 100k
    case N rem 80
      of 
        0 -&gt; receive
	             after 1 -&gt; ok
	         end;
        _ -&gt; []
    end,

% Continue processing the next number
    generate_primes_from(N + 1, Limit, FirstChild).

main() -&gt;
    io:format(&quot;Prime main begins~n&quot;,[]),

% Create a first child to process a value
    ChildFactors2 = spawn(fun prime:print_if_prime/0),

% Tell the child to check values for a factor of 2
    ChildFactors2 ! {you_check, 2},

% Throw a whole range of numbers at the child
    generate_primes_from(2, 10000, ChildFactors2),

% Tell the first child to tell the rest of the children to shutdown
    ChildFactors2 ! {quit, 0},

io:format(&quot;Prime main ends~n&quot;,[]).</pre>
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Pastable version of Experimental Prime Number Generator