In particular, I tried to respect a principle often found in programming languages: user-defined elements (fragments) are no different than builtin ones. For example notice how `page` (which is user-defined) is used in the same way as as `body` (which is builtin) in the first code snippet of the introduction[1].
(In the future, I hope that instead of providing builtins, Slab will instead use libraries of elements. There is an undocumented feature to define elements[2].)
In Pug, to reuse bits of HTML, you can define mixins, but they are called with a `+` sign in front of their name. I also believe mixins can have expression arguments, but not other blocks of HTML. To pass blocks of HTML as "arguments", Pug provides the `extends` keyword, but I think it can only be used at the toplevel of a template. In Slab, the concept of fragments is a bit more uniform: a fragment can be used with expression arguments, and block arguments.
[1]: https://slab-lang.org/reference.html#introduction
[2]: https://github.com/hypered/slab/blob/main/examples/el.slab
Slab was initially a port to Haskell of the Pug.js templating language.
Two, although it's possible to introspect a blaze-html -generated tree, you can't easily have tooling to, say, list HTML fragments, where they are used, which one are full HTML documents (i.e. starting with a doctype)... One of my goal with Slab is to have a "refactorable" language to write "large" HTML code bases (I'm mainly thinking of design systems reference implementations). Having a tool that can "see" the tree structure, the fragment calls, the list of files, ... opens new tooling opportunities.
I'm one of those people that says syntax doesn't matter; we should talk about semantic instead (and thus just adopt s-expressions for syntax). Yet, in this case, I think that a very lightweight syntax that maps clearly to HTML, in particular for non-programmers (e.g. designers), is very valuable.
Note also that I make available a statically-linked `slab` binary that makes super easy to start using Slab. You don't need a programming environment with a compiler and so on. (I'd like to try to create a Cosmopolitan[2] binary in the future.)
The `slab` binary also has a "watch" feature that rebuilds pages and reload the browse as you edit `.slab` files. I guess I mean that having an integrated tool can offer a very good developer (or designer ?) experience.
[1]: https://github.com/hypered/slab/blob/main/content/reference....
