From: Robert Klemme <shortcutter@...>
Date: 2011-05-18T23:54:03+09:00
Subject: Re: Generating Functions in Ruby

On Wed, May 18, 2011 at 3:46 PM, Andreas Lundgren
<andreas.lundgren.x@gmail.com> wrote:
> Hi!
>
> I'm looking for a construction in Ruby to generate a (big) set of
> functions. I need these functions to be class methods and called by
> unique names since they are called via an external API.
>
> As an example, let me create two functions that hard codes an addition
> and then uses this in a small test program.
>
> def FivePlusFour
>  return 5+4
> end
>
> def OnePlusSeven
>  return 1+7
> end
>
> puts("Five + Four is " + FivePlusFour().to_s)
> puts("One + Seven is " + OnePlusSeven().to_s)
>
>
> I would like a way to generate the methods in runtime. As an old C-
> programmer, I'm looking for something like this:
>
> # Define a macro
> define SUM_TEMPLATE(namn,x,y) \\
> def namn \\
>  return x+y \\
> end
>
> # Create each function with a one-liner in runtime.
> SUM_TEMPLATE(FivePlusFour, 5, 4)
> SUM_TEMPLATE(OnePlusSeven, 1, 7)
>
> # Test program
> puts("Five + Four is " + FivePlusFour().to_s)
> puts("One + Seven is " + OnePlusSeven().to_s)
>
> Is this possible in Ruby?

def SUM_TEMPLATE(name, x, y)
  class <<self;self;end.class_eval "def #{name}; #{x} + #{y}; end"
end

> (Please don't reply how to solve this silly example in a better way,
> the true use case is of cause much more complex. But conceptually it's
> the same.)

Is it really?  Do you always have one name and two values as input?
Can you give a bit more contextual information?

Cheers

robert

-- 
remember.guy do |as, often| as.you_can - without end
http://blog.rubybestpractices.com/