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From: Robert Klemme <shortcutter@googlemail.com>
Newsgroups: comp.lang.ruby
Subject: Re: Proposal for easier syntax for define-unless-already-defined pattern
Date: Wed, 30 Jul 2014 19:45:24 +0200
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On 29.07.2014 18:40, Eugene Gilburg wrote:
> Below pattern is very popular in Ruby, but does not work if the
> method returns `nil` or `false`:
>
> @obj ||= some_expensive_method()
>
> For more consistent and efficient use of this pattern, you'd have to
> write:
>
> if defined?(@obj) @obj else @obj = some_expensive_method() end
>
> Because above syntax is clunky, people tend not to use it, with the
> less efficient ||= being far more common.

Where is this less efficient?  I don't think it is.

> So what do you think of `?=` syntax below, to exactly replicate the
> above code block? It should check not value of variable but only
> whether the variable itself is defined:
>
> @obj ?= some_expensive_method()

Operator ||= works remarkably good in practice and for the rare cases 
where #some_expensive_method returns nil or false the user can use the 
test with #defined? explicitly.  Not sure whether that small benefit 
warrants a language change.

Kind regards

	robert