Calling random


#1

Apologies, I have been out of using ruby for a while, and ran into
trouble when I tried to do the below. What is the normal way to call
apply a list of arguments to a list of functions?

def f1(n)
puts “f1: #{n}”
end

def f2(n)
puts “f2: #{n}”
end

irb(main):008:0> [f1,f2].each {|fun| [1,2,3,4].each {|val| fun(val)}}


#2

Sorry for the mismatched title, a more appropriate one would be: “how to
combine a list of functions with a list of arguments?”


#3

Boris S. wrote:

end
[:f1, :f2].each do | fun |
[1, 2, 3, 4].each { | x | Object.send(fun, x) }
end

Ruby doesn’t have functions, just methods. What look like functions
above (a def outside a class body) creates methods in the Object class.

“send” is the generic way to call any object’s method using a name. It
accepts a string or symbol (hence :f1 above) followed by the arguments.

a


#4

Hi –

On Mon, 9 Feb 2009, Boris S. wrote:

end

irb(main):008:0> [f1,f2].each {|fun| [1,2,3,4].each {|val| fun(val)}}

If f1 and f2 contain actual method objects, you can use call:

f1,f2 = method(:f1), method(:f2)
[f1,f2].each {|m| [1,2,3,4].each {|e| m.call(e) } }

Mixing f(unction) and m(ethod) terminology a bit… but that’s OK,
because it will also work if f1 and f2 are Proc objects (which are
basically anonymous functions.

If you have strings or symbols, you can use them to get the method
objects (see above), or you can use send:

[“f1”, “f2”].each {|m| [1,2,3,4].each {|e| send(m,e)} }

David


David A. Black / Ruby Power and Light, LLC
Ruby/Rails consulting & training: http://www.rubypal.com
Coming in 2009: The Well-Grounded Rubyist (http://manning.com/black2)

http://www.wishsight.com => Independent, social wishlist management!


#5

Boris S. wrote:

Am I correct if I remember that using send is quite expensive in
cpu-time? Especially when I am using it millions of times… $pop is
about 5000 hosts large.

Ah. It’s not that bad. send(“fib”,2) is about twice as slow as fib(2).
So I lose 2 minutes in 2 hours of simulation, which is fine.

Thanks for the answers!


#6

Am I correct if I remember that using send is quite expensive in
cpu-time? Especially when I am using it millions of times… $pop is
about 5000 hosts large.

10000.times {
# Events to happen to every host this 0.1 year:
[“birth”,“death”,“infect”,“evolve”].shuffle.each {|event|

   next if event == "birth" and EVENTS_BIRTH > rand
   next if event == "death" and EVENTS_DEATH > rand
   next if event == "infect" and EVENTS_INFECTION > rand
   next if event == "evolve" and EVENTS_EVOLUTION > rand
   $pop.each {|host|
      next if host == nil
      send(event,host)
   }

}
}

What I could do is make birth,death,infect and evolve methods of the
host class, and perhaps use call then. Does that make sense?

David A. Black wrote:

Hi –

On Mon, 9 Feb 2009, Boris S. wrote:

end

irb(main):008:0> [f1,f2].each {|fun| [1,2,3,4].each {|val| fun(val)}}

If f1 and f2 contain actual method objects, you can use call:

f1,f2 = method(:f1), method(:f2)
[f1,f2].each {|m| [1,2,3,4].each {|e| m.call(e) } }

Mixing f(unction) and m(ethod) terminology a bit… but that’s OK,
because it will also work if f1 and f2 are Proc objects (which are
basically anonymous functions.

If you have strings or symbols, you can use them to get the method
objects (see above), or you can use send:

[“f1”, “f2”].each {|m| [1,2,3,4].each {|e| send(m,e)} }

David


David A. Black / Ruby Power and Light, LLC
Ruby/Rails consulting & training: http://www.rubypal.com
Coming in 2009: The Well-Grounded Rubyist (http://manning.com/black2)

http://www.wishsight.com => Independent, social wishlist management!


#7

Boris S. wrote:

Am I correct if I remember that using send is quite expensive in
cpu-time? Especially when I am using it millions of times… $pop is
about 5000 hosts large.

10000.times {
# Events to happen to every host this 0.1 year:
[“birth”,“death”,“infect”,“evolve”].shuffle.each {|event|

Using #send with a String argument is slower than using it with a
Symbol. Benchmark:


require ‘benchmark’
class Foo
def bar; end
end

a_foo = Foo.new

TIMES = 1_000_000

puts “Direct”, Benchmark::measure { TIMES.times { a_foo.bar } }
puts “Symbol”, Benchmark::measure { TIMES.times { a_foo.send(:bar) }
puts “String”, Benchmark::measure { TIMES.times { a_foo.send(“bar”) } }

With Ruby 1.8:

Direct
0.290000 0.000000 0.290000 ( 0.294786)
Symbol
0.380000 0.000000 0.380000 ( 0.385319)
String
0.550000 0.000000 0.550000 ( 0.556780)

With Ruby 1.9, the difference between #send(a_symbol) and calling the
method directly is negligible:

Direct
0.210000 0.000000 0.210000 ( 0.209512)
Symbol
0.210000 0.000000 0.210000 ( 0.210357)
String
0.490000 0.000000 0.490000 ( 0.500568)

alex


#8

Hi –

On Mon, 9 Feb 2009, Alex F. wrote:

Benchmark:

0.380000 0.000000 0.380000 ( 0.385319)
String
0.490000 0.000000 0.490000 ( 0.500568)

However, calling #intern/to_sym is (slightly) slower than just sending
a string. This is Ruby 1.9.1:

Direct
0.150000 0.000000 0.150000 ( 0.157290)
Symbol
0.170000 0.000000 0.170000 ( 0.166353)
String
0.470000 0.000000 0.470000 ( 0.476854)
#intern
0.520000 0.020000 0.540000 ( 0.537574)

So if you’ve got a string already, it’s probably not worth doing the
conversion explicitly.

David


David A. Black / Ruby Power and Light, LLC
Ruby/Rails consulting & training: http://www.rubypal.com
Coming in 2009: The Well-Grounded Rubyist (http://manning.com/black2)

http://www.wishsight.com => Independent, social wishlist management!


#9

On Sun, 08 Feb 2009 15:56:04 -0500, Boris S. wrote:

Boris S. wrote:

Am I correct if I remember that using send is quite expensive in
cpu-time? Especially when I am using it millions of times… $pop is
about 5000 hosts large.

Ah. It’s not that bad. send(“fib”,2) is about twice as slow as fib(2).
So I lose 2 minutes in 2 hours of simulation, which is fine.

Thanks for the answers!

It should be a bit faster if you use :fib instead of “fib”, because the
ruby runtime has to internally “fib” to :fib every time you call send().

–Ken


#10

On Mon, Feb 9, 2009 at 2:16 AM, Boris S. removed_email_address@domain.invalid
wrote:

Sorry for the mismatched title, a more appropriate one would be: “how to
combine a list of functions with a list of arguments?”

Posted via http://www.ruby-forum.com/.

I’m taking a stab in the dark here but are you trying to pass more than one
procedures as arguments to a function?
if so, then try:
def foo(x, y)
x.call
y.call
end

foo proc { puts ‘x’ }, proc { puts ‘y’ }

Anyway i could spend hours trying to understand that question.


#11

On Mon, Feb 09, 2009 at 07:15:35AM +0900, David A. Black wrote:

#intern
0.520000 0.020000 0.540000 ( 0.537574)

So if you’ve got a string already, it’s probably not worth doing the
conversion explicitly.

It’s probably worth it if you can organize your code to do explicity
conversion once vs. doing implict conversion through many iterations,
though.


#12

Huh?

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