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From: 7stud -- <bbxx789_05ss@yahoo.com>
Newsgroups: comp.lang.ruby
Subject: Re: Generating Functions in Ruby
Date: Tue, 24 May 2011 17:53:54 -0500
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7stud -- wrote in post #1000754:
> Andreas Lundgren wrote in post #1000535:
>> First params does not contain a simple string;
>> please note the escaped string characters in the code
>> that generates params. Kind of strings within strings
>
> What I failed to recognize was that the line:
>
>   params = #{params}
>
> was part of a multiline string.
>
>
>
>> "1) Strings are mutable in ruby, so get rid of all those +'s." - I'm
>> not sure that I understand this but it sounds interesting, what does
>> it mean?
>>
>
> Every quoting mechanism creates a string and every + creates a new
> combined string.  So it's more efficient to use string interpolation:
>
> i = 2
> params = 'x1.to_s'
> params = "#{params}, x#{i}.to_s"
> p params
>
> --output:--
> "x1.to_s, x2.to_s"
>
>
> In ruby not only can you push elements onto an array with the << method,
> you can also use the << method to push a string onto another
> string--which
> alters the first string:
>
>
> i = 2
> params = 'x1.to_s'
> params = "#{params}, x#{i}.to_s"
>
> puts params
> puts params.object_id
>
> params << ', x3.to_s'
>
> puts params
> puts params.object_id
>
> --output:--
> x1.to_s, x2.to_s
> 77684510
> x1.to_s, x2.to_s, x3.to_s
> 77684510

So your loop here:

    params = 'x1.to_s';
    for i in 2..no_of_params do
      arg_list = arg_list + ', x' + i.to_s;
      params = params + ' + \', \' + x' + i.to_s + '.to_s';
    end
    params = params+';';


would simplify to:


num_params = 4
params = 'x1.to_s'

2.upto(num_params).each do |i|
  params <<  ", x#{i}.to_s"
end

p params

--output:--
"x1.to_s, x2.to_s, x3.to_s, x4.to_s"


Also, compare that output to the output your loop produces:

  "x1.to_s + ', ' + x2.to_s + ', ' + x3.to_s + ', ' + x4.to_s"

You would get many errors using that string as an argument list for a 
method.

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