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Ruby lamdba 相等性？

伊謝爾倫 2017-04-24 09:11:42

733

HI，以下是小弟的嘗試：

p=lambda {|x| x*x}
q=p.dup
puts q==p　#out false
puts p.object_id
puts q.object_id

為什么是false呢？

伊謝爾倫

小伙看你根骨奇佳，潛力無(wú)限，來(lái)學(xué)PHP伐。

reply all(2)

Ty802017-04-24 09:13:42 2 floor

Version problem.

This book of yours should be relatively old, and the Ruby version you are using is before 2.0. Starting with Ruby 2.0, the behavior of Proc#== has changed:

Starting with Ruby 2.0, Two procs are == only when they are the same object.只有當(dāng)兩個(gè) proc 是同一對(duì)象時(shí)，== 才返回 true.

Reference:

https://bugs.ruby-lang.org/issues/4559
https://github.com/ruby/ruby/blob/f031aec4233d7a6d4622c048abed3e86eb5dd6c2/NEWS#L127-130

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Peter_Zhu2017-04-24 09:13:42 1 floor

Looking at ruby’s official documentation, lambda is actually Proc.
Proc does not overload its own == method, but calls BasicObject
’s == method

Equality — At the Object level, == returns true only if obj and other are the same object (The method of comparing objects at the Object level is to determine whether they are the same object).
Typically, this method is overridden in descendant classes to provide class-specific meaning.

Proc

Look at the base class of Proc and you can see that it inherits from Object, and then Object inherits from BasicObject

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