[Haskell-cafe] Design of an extensible system

[Jeremy O'Donoghue]

> On 24 Jul 2018, at 15:16, Paul <aquagnu at gmail.com> wrote:
> 
> > that Pandoc supported dynamically loading of extra plugins on demand.
> 
> It means .dll/.so. But also there are applications with pre-built "plugins" - you can not load them dynamically, but can turn-on/off dynamically (from a list of pre-installed plugins). It's useful too.
> 
Pandoc plug-ins are separate executables rather than shared libraries. Haskell data types are serialised by Pandoc then de-serialised, modified and re-serialised in each plugin.

The Pandoc approach is more like a data pipeline with Pandoc itself at both ends.

Jeremy 

> 24.07.2018 09:07, Marc Busqué wrotes:
>> On Mon, 23 Jul 2018, John Lato wrote: 
>> 
>>> I think you're attempting to optimize the wrong thing. In a dynamic language like Ruby, this approach makes sense because download times are a 
>>> significant fraction of the user's time, and otherwise the user experience isn't affected much because the code is basically interpreted either 
>>> way. 
>>> Haskell is primarily a compiled language. The total download size probably won't be significantly larger from downloading all modules. The cost 
>>> of recompiling/dynamically loading plugins will be expensive (relative to the rest of the user time), and payed with every execution. Plus it's 
>>> additional work for the developer to set up. 
>> 
>> What you say makes a lot of sense in terms of optimization. But, what 
>> about extensibility? Take for example the Pandoc package, which would be 
>> similar in design of what I'm trying to do. Say I want to add a 
>> converter to some mark-up format not supported by Pandoc, and that 
>> Pandoc team doesn't agree to merge my work in its repo or simply I don't 
>> have the time to wait until it happens. In this sense, it would be nice 
>> that Pandoc supported dynamically loading of extra plugins on demand. 
>> 
>> Marc Busqué 
>> http://waiting-for-dev.github.io/about/
>> 
>> 
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