[Top][All Lists]

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: Update on Eliminating Singleton Objects

From: John W. Eaton
Subject: Re: Update on Eliminating Singleton Objects
Date: Mon, 8 Jan 2018 11:12:37 -0500
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.4.0

On 01/07/2018 08:28 PM, Rik wrote:

This is a lot of code re-factoring.  Are there other benefits besides being
able to run multiple interpreters out of the same program (which sounds
like an edge use case)?  Is there an impact on performance if every
function call has to push a pointer to the current interpreter on to the
stack before executing?

These are good questions.

I think it makes the interpreter easier to understand if the objects that it is composed of are members of the interpreter object itself rather than just a bunch of other global objects, which was the case when pretty much everything was a singleton object or just some other global thing like the lexer and parser. I think it will also help with memory issues if, as much as possible, we manage all resources in constructors/destructors. Moving away from the singleton pattern should help do that for the interpreter itself.

If there are performance issues, then I think we can fix them by allowing more direct access to the interpreter object and its components where it is necessary. But unless there really is a performance issue, I'd prefer to use member functions or pass a reference to the interpreter object. I think eliminating globals makes the code easier to understand and modify, but maybe it is not so critical if the only real global object is the interpreter itself.

I know, it was my fault for introducing the singleton pattern in Octave. But Jordi finally convinced me that it wasn't the best idea... Where possible, I want to convert these global objects to be data members of some other object. Typically that means making them part of the interpreter object. But if they need to remain global, that's OK, but I want their lifetimes to be clear and predictible.

Anyway, I'm open to discussion. If these goals are wrong or misguided, then let me know.


reply via email to

[Prev in Thread] Current Thread [Next in Thread]