Re: set vs copy?
Re: set vs copy?
- Subject: Re: set vs copy?
- From: Shane Stanley <email@hidden>
- Date: Wed, 15 Sep 2010 08:38:57 +1000
- Thread-topic: set vs copy?
On 15/9/10 7:01 AM, "tom wible" <email@hidden> wrote:
>> For paranoia's sake, I used copy, but I'm sure a set will do the
>> trick.
>
> i've never seen a satisfactory explanation of exactly what a/s is
> doing in set vs copy...
Copy makes a complete copy of what a variable refers to, whereas set just
makes another variable pointing to the same stuff in memory.
For mutable classes like list, record and date, having more than one
variable point to the same chunk of memory means that if you modify the
contents of one of these variables, any others pointing to the same chunk of
memory will also return the new value. This can be avoided, where necessary,
by using copy to make an entirely separate, um, copy.
For immutable classes like text, real, etc, the fact that more than one
variable can point to the same chunk of memory is irrelevant, because the
contents can't be modified once it's created anyway. So doing a copy in such
cases is just wasting time and memory.
--
Shane Stanley <email@hidden>
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