Re: sfx: baby steps of an html templating engine based on skribillo's skribe reader and sxml

[Amirouche Boubekki]

I improved the usuability of the module. It should be able to just drop 
`sfx.scm` in your project to use it.

Here an exemple use in scheme code:

;;;
;;; This requires at least a `index.sfx` file and `person.scm` where
;;; a `<person>` record is defined.
;;;

;; (use-modules (person))

;; (define persons (list (make-person "amirouche" 30)
;;                       (make-person "julien" 30)
;;                       (make-person "mez" 27)
;;                       (make-person "moh" 113)))

;; (define bindings `((value ,(make-parameter 42))
;;                    (title '(h1 "Héllo (again (and again)) hacker!"))
;;                    (persons ,persons)))

;; (with-output-to-file "index.html"
;;   (lambda () (render "index.sfx" bindings)))

I attached the updated `sfx.scm` with required files to test it.

There still one area where it can be improved regarding template 
resolution/finding. Right now it simply look for templates according the 
default `(open)` behavior which looks
in cwd (current working directory).


Best regards

Le 2015-07-30 18:52, Amirouche Boubekki a écrit :
> Le 2015-07-30 13:55, Amirouche Boubekki a écrit :
> > Héllo,
> >
> >
> > I've been lurking around skribillo and artanis. I don't really like
> > the rails-like syntax
> > of artanis, even if it has its use-cases and I wanted to hack on
> > something "small", so
> > I've put together sfx.
> >
> > The code of skribe reader is included in sfx.scm. So the only
> > dependency is guile (2.0.11) and
> > guile-reader that you can install using `guix package -i 
> > guile-reader`.
> >
> > This bare template language has the following features:
> >
> > - wanna be simpler sxml syntax
> > - templates with custom environment
> > - external libraries loading inside the template
> >
> >
> > # Wanna be simpler sxml syntax
> >
> > Skribe reader (implemented with guile-reader) provide a handy syntax 
> > to
> > both define keywords and quasiquote. In an sxml context those features
> > are used to implemented attributes and text nodes.
> >
> > ## attributes
> >
> > Attributes in sxml are defined as follow:
> >
> >   (div (@ (id "shell")) "This the main area")
> >
> > Instead of requiring the nesting of `(attribute-name attribute-value)` 
> > sfx use
> > the simpler keyword syntax `:keyword`. The above snippet becomes:
> >
> >   (div (@ :id "shell") "This the main area")
> >
> > I'm not sure it's worth the trouble of diverting from sxml standard.
> > That said, it looks
> > more like plain xml.
> >
> > ## text nodes
> >
> > Text nodes can be defined as
> >
> >   (p [héllo hacker])
> >
> > This is looks the same as the default reader. It becomes handy when
> > you include an
> > inline element inside the text node:
> >
> >   (p [héllo ,(b [hacker])
> >
> > `,()` is a special syntax of skribe reader which provides `(unquote)`
> > inside [bracket] `quasiquote`.
> >
> > With the default guile reader, this must be written as:
> >
> >   (p "héllo " (b "hacker"))
> >
> > This is looks verbose and prone to error. One must not forget the 
> > space in the
> > string before the `(b)` element.
> >
> >
> > # templates with custom environment
> >
> > Right now this part of the template language is not really
> > userfriendly. But you can pass custom
> > variables to the template but those must be parameters. In the example
> > sfx.scm (which includes
> > example use of the procedures) the environment in which the template
> > is evaled is defined as follow:
> >
> >   (define value (make-parameter 42))
> >   (define amirouche (make-person "amirouche" 30))
> >   (define env (let ((value value)
> >                     (amirouche amirouche))
> >                 (the-environment)))
> >
> >
> > Then `value` can be echo'ed inside the template using the unquote
> > syntax `,()`, e.g.
> >
> >    (p [Here is a lucky number for you «,(value)»])
> >
> > As you can see the previous snippet, there is also a `<record>` record
> > inside the environment.
> > One can (maybe) provide in the environment the required procedures to
> > echo the correct
> > fields but this is verbose. Instead sfx use `(use-modules)` inside the
> > template definition
> > file. This is presented in the following and last part.
> >
> > # external libraries loading inside the template
> >
> > Currently it's (only) possible to do `(use-modules)` inside the
> > template file. The template
> > file looks like the following:
> >
> > ```
> > (use-modules (person))
> >
> > `(html
> >   (body
> >     (p [My name is ,(person-name amirouche)])))
> > ```
> >
> > I could not make procedure definition work inside the template, this
> > my be linked to the way
> > I eval the template. It's shame because for quick and dirty hacks it
> > can be handy like defining
> > mini-templates inside the big template.
> >
> >
> >
> >
> >
> > This is my second try at this and having a look at the code of haunt
> > [1] was helpful.
> >
> > Hope this helps!
> >
> >
> > [1] https://git.dthompson.us/haunt.git
>
> Sorry for the double posting. This mail is not a duplicate.
>
> I though that the implementation `extend` would be more involving.
>
> `extend` is the dual of `include`. Given a base template `base.sfx`
> you define placeholders
> say `,(main)` and `,(sidebar)` and the rest is the "shell" of the
> application ie. the part of
> GUI that is always the same over the application.
>
> If `index.sfx` inherit `base.sfx` the context in which `base.sfx` is
> rendered is the same as the context
> used to render `ìndex.sfx` plus the variables defined/passed in
> `ìndex.sfx` to `base.sfx`.
>
> In the following example, `title` and `intro` are evaled and then
> added to `(current-module)` environment
> with which `base.sfx` is rendered.
>
>    (extend "base.sfx"
>            (current-module)
>            `((title `(h1 [Héllo again hacker!!]))
>              (intro "This is a little presentation of sfx template 
> language")))
>
> I don't how to make `(current-module)` disappear but it's also more
> explicit. I'm not sure.
>
> `extend` implement a pattern similar to inheritance in OOP.
>
> I attach complete code with an example. There is small doc in the
> header of the file.

--
Amirouche ~ amz3 ~ http://www.hyperdev.fr

sfx.scm
Description: Text document

base.sfx
Description: Text document

index.sfx
Description: Text document

person.scm
Description: Text document