DZone Snippets: methods code

Optimization - Minimum - Search and Golden Rule

lrei (Luis Rei) — Sun, 15 Jun 2008 15:43:19 GMT



from math import sin

def f(x):

    return ((x**4))



def optMinSearch(f, xi, h, t=1.0e-9):

    ssx = xi

    x = xi

    fx = f(x)

    sx = x

    x += h

    fxn = f(x)

    n = 0



    while abs(fxn-fx) > t :

        while fx > fxn:

            n += 1

            fx = fxn

            ssx = sx

            sx = x

            x += h

            fxn = f(x)

    

        xx = x

        h = h / 2

        x = ssx

        fx = f(x)

        sx = x

        x += h

        fxn = f(x)

        n += 1

    

    

    return x, fxn, n, sx, xx





    



def optMinGold(f, xi, xf, t=1.0e-9):

    # constants

    A = 0.6180339887

    

    n = 0

    

    x1 = xi

    x2 = xf



    x3 = x1 + A * (x2-x1)

    x4 = x2 - A * (x2-x1)

    

    fx3 = f(x3)

    fx4 = f(x4)

    

    while abs(x2-x1) > t:

        #print n, x1, x2, abs(x2-x1)

        n+=1

        if fx3 < fx4:

        # fx4 > fx3

            x1 = x4

            x4 = x3

            x3 = x1 + A * (x2-x1)

        else:

         # fx4 < fx3

            x2 = x3

            x3 = x4

            x4 = x2 - A * (x2-x1)

        

        fx3 = f(x3)

        fx4 = f(x4)

        

    return (x1,x2,n)





xmin, fmin, n, sx, xx = optMinSearch(f, -2.0, 0.1)

print xmin

print fmin

print n

print "-----"





(x1,x2,n) = optMinGold(f, -2.0, 2.0)

print x1

print f(x1)

print x2

print f(x2)

print n

Ruby IRB helper method to pretty-print object methods

conorh (Conor Hunt) — Fri, 27 Oct 2006 23:08:01 GMT

A simple method to print out the methods for an object at run time in a nicely formatted and colorized way. Really useful when using irb

Place in your .irbrc for easy usage, example here:
http://dotfiles.org/~sd/.irbrc

usage:
pm object
pm object, :more - shows all methods including base Object methods
pm object, :more, /to/ - shows all methods filtered by regexp

Coded by sebastian delmont



    ANSI_BOLD       = "\033[1m"

    ANSI_RESET      = "\033[0m"

    ANSI_LGRAY    = "\033[0;37m"

    ANSI_GRAY     = "\033[1;30m"



    def pm(obj, *options) # Print methods

      methods = obj.methods

      methods -= Object.methods unless options.include? :more

      filter = options.select {|opt| opt.kind_of? Regexp}.first

      methods = methods.select {|name| name =~ filter} if filter



      data = methods.sort.collect do |name|

        method = obj.method(name)

        if method.arity == 0

          args = "()"

        elsif method.arity > 0

          n = method.arity

          args = "(#{(1..n).collect {|i| "arg#{i}"}.join(", ")})"

        elsif method.arity < 0

          n = -method.arity

          args = "(#{(1..n).collect {|i| "arg#{i}"}.join(", ")}, ...)"

        end

        klass = $1 if method.inspect =~ /Method: (.*?)#/

        [name, args, klass]

      end

      max_name = data.collect {|item| item[0].size}.max

      max_args = data.collect {|item| item[1].size}.max

      data.each do |item| 

        print " #{ANSI_BOLD}#{item[0].rjust(max_name)}#{ANSI_RESET}"

        print "#{ANSI_GRAY}#{item[1].ljust(max_args)}#{ANSI_RESET}"

        print "   #{ANSI_LGRAY}#{item[2]}#{ANSI_RESET}\n"

      end

      data.size

    end

Get the name of the current method in Ruby

jswizard (JavaScript Wizard) — Fri, 04 Aug 2006 19:22:00 GMT

Found at http://nubyonrails.com/articles/2006/08/04/seattle-rbbq



def method_name

  if  /`(.*)'/.match(caller.first)

    return $1

  end

  nil

end



def blah

  puts method_name

end



blah  # => 'blah'

Using Ruby hashes as keyword arguments, with easy defaults

lukeredpath (Luke Redpath) — Thu, 27 Jul 2006 13:17:06 GMT

Similar to many Rails helpers/methods, a lot of the methods I write often use an optional hash of options, or sometimes just a hash only, to simulate keyword arguments (often using symbols).

The only downside to doing this is you lose out on easily setting default values using Ruby's default method argument values. You might use code something similar to the following to make up for this:



def some_method(opts={})

  my_foo =  opts[:foo] || 'mydefaultfoo'

end

However, as you have more and more keyword options, setting defaults in this way gets rather tedious. Fortunately, Ruby's Hash#merge comes to our rescue (almost) - it allows you to merge the contents of one hash with another. The only problem - any duplicate keys in the hash you are merging will overwrite your original hash values - when it comes to setting default values, we want this to work the other way around; we only want values in the defaults hash to be merged if they do not exist in the original hash. Again, Ruby comes to our rescue - Hash#merge takes a block as an argument and will pass any duplicate values that crop up into the block - we can use this block to decide which value to keep.

Using the simple monkey patch to the Hash class below, you will no longer have to set each default individually:



class Hash

  def with_defaults(defaults)

    self.merge(defaults) { |key, old, new| old.nil? ? new : old } 

  end



  def with_defaults!(defaults)

    self.merge!(defaults) { |key, old, new| old.nil? ? new : old }

  end

end

Of course, sticking with Ruby naming conventions, with_defaults() will return a new hash whilst with_defaults!() will change the original hash directly.

See http://www.lukeredpath.co.uk/index.php/2006/07/27/using-ruby-hashes-as-keyword-arguments-with-easy-defaults/ for further discussion and alternatives.

Temporarily overriding class methods in Ruby

peter (Peter Cooperx) — Sun, 09 Apr 2006 23:42:56 GMT

By Tobi / xal from IRC, and seemingly related to this.

class Object

  def mock_methods(mock_methods)

 

    original = self

 

    klass = Class.new(self) do

 

      instance_eval do       

        mock_methods.each do |method, proc| 

          define_method("mocked_#{method}", &proc)

          alias_method method, "mocked_#{method}"

        end            

      end

 

    end

 

    begin

      Object.send(:remove_const, self.name.to_s)

      Object.const_set(self.name.intern, klass)

 

      yield

 

    ensure

      Object.send(:remove_const, self.name.to_s)

      Object.const_set(self.name.intern, original)

    end

 

  end

end

 

class Duck

  def quak; puts "Quak";  end

end

 

Duck.new.quak #=> "Quak"

 

Duck.mock_methods(:quak => Proc.new { puts 'Wuff' }) do  

  Duck.new.quak #=> "Wuff"

end

Example of Detecting Subclasses

jimweirich (Jim Weirich) — Wed, 13 Apr 2005 11:03:57 GMT

class A
def A.inherited(clazz)
puts "Hey, #{clazz} is subclassing me"
end
end

class B < A; end

Produces:

$ ruby x.rb
Hey, B is subclassing me