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Cheaper alternative to Binding.of_caller

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Eigen Class

Posts: 358
Nickname: eigenclass
Registered: Oct, 2005

Eigenclass is a hardcore Ruby blog.

Cheaper alternative to Binding.of_caller

Posted: Jul 20, 2006 6:05 AM

This post originated from an RSS feed registered with Ruby Buzz by Eigen Class.
Original Post: Cheaper alternative to Binding.of_caller Feed Title: Eigenclass Feed URL: http://feeds.feedburner.com/eigenclass Feed Description: Ruby stuff --- trying to stay away from triviality.	Latest Ruby Buzz Posts Latest Ruby Buzz Posts by Eigen Class Latest Posts From Eigenclass

Here's a trick to modify local variables in the caller scope without using Binding.of_caller. It's not as general, but much faster when it applies (when you're using a "literal" block):

def foo(a, &block)
  raise "Want a block" unless block_given?
  eval("lambda{|x| whatever = x}", block).call(1)
  yield a + 1
end

whatever = nil
a = foo(1){|x| 2 * x }
whatever                          # => 1
a                                 # => 4

Why use

  eval("lambda{|x| whatever = x}", block).call(1)

instead of simply

  eval("whatever = 1", block)

? The example is admittedly stupid, since in a less simplistic (but rare!) situation you'd have something more like

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