[Haskell-cafe] ANN: nice-html, an all-around "nice" html templating library, similar but different to lucid, blaze, type-of-html, etc.

[Mike Ledger]

>Do you mind explaining the invalid monad instance of Lucid and how it
would impact a library user?
To my knowledge lucid uses a monad instance that follow the monad laws
(what I meant by "valid") fine.

It's blaze that's (somewhat) infamous for having an invalid monad instance.
It used to be the case that (>>=) in blaze called 'error' -- the Monad
instance was to just use (>>) = mappend. Looking now, the implementation
has changed and my knowledge was out-of-date. I think it still violates the
monad laws, but I don't know if as a user of blaze you'd ever be able to
actually observe this, if that makes any sense.

For some fun discussions on this see:
-
https://stackoverflow.com/questions/6399648/what-happens-to-you-if-you-break-the-monad-laws
-
https://www.reddit.com/r/haskell/comments/16iakr/what_happens_when_a_monad_violates_monadic_laws/

How invalid monads *can* impact users is better explored in the SO question.

>Also, I'm assuming one shouldn't call the `compile` function each time a
page needs to be rendered, right? Should one put the results of the
`compile` function in a top-level Map and use those to get the speed gains?
The idea is to only compile a template once, ever. If you need to compile a
template every time a page is rendered (though I can't actually think of a
case where you would), you should probably just skip the middle-man, and
use lucid (or blaze). It's not horribly slow, but you'd miss out on the
benefits of nice-html by doing this.

Cheers

On Thu, Oct 26, 2017 at 11:51 PM, Saurabh Nanda <saurabhnanda at gmail.com>
wrote:

> Thank you for putting comparisons and benchmarks, upfront.
>
> Do you mind explaining the invalid monad instance of Lucid and how it
> would impact a library user?
>
> Also, I'm assuming one shouldn't call the `compile` function each time a
> page needs to be rendered, right? Should one put the results of the
> `compile` function in a top-level Map and use those to get the speed gains?
>
> Side comment, the use of `dynamic` makes it look similar to reflex `dyn*`
> API.
>
> -- Saurabh.
>
> On Thu, Oct 26, 2017 at 4:15 PM, Mike Ledger <eleventynine at gmail.com>
> wrote:
>
>> Hi Haskell-Cafe,
>>
>> I've been working on and off on a HTML templating library that is
>> slightly novel for a few months.
>>
>> Here's the good parts:
>> * it's faster than lucid and blaze
>> * it has a valid monad instance
>> * it has another valid monad instance, that is slightly different!
>> * it paramaterises templates by the data they require
>> * the HTML5 combinators don't rely on any highly overloaded/overlapping
>> typeclasses; type errors in nice-html templates tend to be nice monomorphic
>> type mismatches
>>
>> To achieve this, it has a distinct compilation phase (at runtime) for
>> templates. This means the actual rendering function does very little beyond
>> concatenate Text and escape dynamic input. It also severely restricts usage
>> to the built-in combinators available -- at least, for dynamic data -- and
>> can make writing a nice-html template difficult, though littering _
>> throughout type signatures helps.
>>
>> Check it out!
>>
>> Benchmark results, a README, and an example:
>> https://github.com/TransportEngineering/nice-html
>> Hackage: https://hackage.haskell.org/package/nice-html
>>
>> The only thing on the roadmap right now is to have some nice :-) way to
>> assign JavaScript event handlers to Markup. This is something that I really
>> appreciate when using React.js, so my eventual aim is for nice-html to be
>> like a (more) server-side version of React. Right now, you can keep track
>> of element ids with `Text.Html.Writer.note`, but it's neither a very good
>> nor very useful interface.
>>
>> Cheers,
>> Mike
>>
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>
>
>
> --
> http://www.saurabhnanda.com
>
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