[TxMt] Re: run_script.rb

Charles Turner vze26m98 at optonline.net
Mon Aug 25 13:07:45 UTC 2008

On Mon, 25 Aug 2008 07:39:26 -0500, James Gray wrote:

>>>   str.send(str.respond_to?(:lines) ? :lines, :to_s).map { … }

> You didn't read my code very well.  Please scroll up and have another  
> look.  :)

Please forgive my ignorance of Ruby. I was confused by the comma after 
:lines, which my Rubies complain about. I substituted a colon, but 
maybe (again) that's not what you're trying to say?

I read your above as: "if the receiver responds to :lines, send :lines, 
else send :to_s", which in 1.8's case is effectively a NoOp: a 
conversion of a string to a string?

I do see now that :lines is a 1.9-only method, and so your test is a 
smart one.

>> The next trick is sending a symbol. It looks like in 1.8 you can say
>> "a.send(:map)", but the equivalent "a.send(:each_line.to_a.map)" isn't
>> a valid symbol reference in Ruby.
> Those two pieces of code are not equivalent.  In the first, you send()  
> a Symbol message to the object.  In the second, you are calling to_a()  
> on a Symbol.

Thanks for the clarification/analysis of my (incorrect) code!

>> a.respond_to?(:map) ? a.map : a.each_line.to_a.map do |line| print  
>> line
>> end
>> which works for 1.9, but doesn't in 1.8

> Thus, in 1.9, it is legal to call map() without a block as you  
> do above.  The same is not legal in 1.8.
> Hope that answers some of your questions.

Again, thanks for the clarification/education.

Best, Charles

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