[ruby-talk:11689] Re: Putting methods in arrays

Dave Thomas <[e-mail]> writes:

>Alex McHale <[e-mail]> writes:

>>   I'm looking to put a method in an array, to be called at a later time.  
>> In C, this is possible using pointers (through some rigamarole and 
>> typedefs, it would  look like { funct }).  Is there any way this can 
>> similarly be acheived in Ruby?
>>   What the end goal is to be able to call the method using 'arr[index] 
>> args'.  The purpose of this is that I'm working on a server that might 
>> receive one of hundreds of commands from the client side, and this:

>...

>>   Is this possible?  Is there a better solution for command recognition 
>> without endless if/elsif/..?

[snip Dave's 4 ideas]

I was looking for something similar last week.  What I came up with
was:

5.  Convert the function to a Proc object and invoke it with the []
    method.

On my toy factorial problem (shown below), I only saw a difference
of less than 2 percent between the running times for the direct and
indirect calls.  This may also be considered a candidate for the
"Useless and Misleading Benchmark of the Week" award.  

What I was testing for was whether or not calling a simple function many
times via a Proc object would be noticeably slower than the direct call.
This was in the context of wanting to specialize a function at runtime 
based on information not available when the function was written.  More
specifically, I was looking to do something along the lines of partial
function application in SML or a similar effect in e.g. lisp with "let"
and "lambda".

def fac(n)
    acc = 1
    i = 1
    while i < n
        i += 1
        acc *= i
    end
    acc
end

ntimes = 5000
targ = 100

fac2 = Proc.new {|n| fac(n)}

start = Time.now

ntimes.times { fac targ }

direct = Time.now

ntimes.times { fac2[targ] }

indirect = Time.now

print "#{ntimes} direct calls took #{direct - start} seconds.\n"
print "#{ntimes} indirect calls took #{indirect - direct} seconds.\n"


Mike
-- 
Michael Zawrotny
411 Molecular Biophysics Building
Florida State University		| email:  [e-mail]
Tallahassee, FL 32306-4380		| phone:  [phone]