Add info about performance considerations

[kennyjwilli]

The performance differences between using forms handled by Sablono's compile-form and not are not documented. Because the difference is so significant, I think it is worth adding to the README.

[rauhs]

I actually added some of these thoughts a while back to:

https://github.com/r0man/sablono/wiki/Optimization-Tips

Also talks about code size (hence avoiding for). A few weeks ago I also wanted to make sure to never call interpret in my app. Since I got tired of adding ^String typehints all over my code and double checking everything, I decided to just remove the intepret altogether. I.e. you'll get an error if you don't precompile your code. It's an ugly hack but it works:

https://gist.github.com/rauhs/38b8598c6549f2fe09ad4d257382ec32

I agree there should be some awareness of interpret vs compile during macro expansion since that gives rum a speedup of roughly 2x over reagent.

[kennyjwilli]

It almost seems like there should be a dynamic var, similar to *warn-on-reflection*, that allows you to get warning messages when the interpreter is called. Also, maybe another dynamic var that would allow you to turn off interpretation all together (probably worth creating an issue in Sablono for these features).

The problem with using mapv instead of for is you don't get the pre-compilation, making your render time basically the same as using map.

I have also submitted r0man/sablono#135 which lets you use a shorter metadata tag :inline to skip compilation (it also makes more sense in the general case -- it doesn't make sense to type hint a function that returns a React component as a String).

[roman01la]

Hello. New maintainer here 👋

It's good to be aware of these differences, but I'd also rephrase the text so it doesn't feel like it pushes you towards refactoring your project and keeping an eye on the code to be specifically written for Sablono.

Interpreter improvements are on my roadmap. Currently Sablono is much slower than Reagent in interpretation mode, unfortunately.

[roman01la]

Added rum.core/set-warn-on-interpretation! here 66d352a