From: Brian Candler <lists@...>
Date: 2012-09-25T01:23:05+09:00
Subject: Re: How would you allow variable from specific list of Fixnum?

Eliezer Croitoru wrote in post #1077009:
> If there is not difference in the operation such as in:
> newregex = /[\d]+/
> newregex = Regexp.new("[\\d]+")
>
> so there is not really a good reason to use one or the other since the
> result is the same.

In the first, you are using a Regexp literal. This is immutable, and you 
will get the same object_id each time round a loop.

In the second, inside Regexp.new you are using a string literal - which 
is mutable and gets a different object_id each time round a loop. And 
therefore a new Regexp has to be built each time, because Ruby doesn't 
know that the String actually has the same contents.

>> 3.times { puts /\d+/.object_id; puts Regexp.new("/\\d+/").object_id }
2165193160
2165191640
2165193160
2165191560
2165193160
2165191480

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