ajay paswan wrote in post #1072056:
> What is the best and complete book for ruby.
> To be specific I want to learn the following things apart from
> understanding the language:
> 1. thread handling.
> 2. Code efficiency, i.e. the time-cost of each instruction.

I would agree with Pickaxe, a.k.a. Programming Ruby - 2nd edition if you 
are using 1.8, 3rd edition if you are using 1.9. The 1st edition is 
online for free:
http://ruby-doc.org/docs/ProgrammingRuby/

As for "the time-cost of each instruction" you're not going to get much 
help from any book. You need to profile your code - e.g. using the 
Benchmark library or ruby-prof; identify where the hot-spots are, and 
then optimise.

Ruby is a dynamic language and it all boils down to method dispatch. 
e.g.

a + b

is exactly the same as a.+(b), or a.send(:+, b)

If you have a hotspot which you can't improve using Ruby, then you can 
always rewrite that part in C using the RubyInline gem.

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