[erlang-questions] [ANN] Brim - HTML templating library

Thu Mar 15 21:57:37 CET 2012

Just for grins, let's look at another way of doing it,
using another programming language.

On 16/03/2012, at 1:17 AM, Michael Turner wrote:

> <html><head><title>The title</title></head><body>The body</body></html>

Change it to
<html>
 <head>
  <title><span class="C:replace">TITLE</span></title>
 </head>
 <body>
  <p><span class="C:replace">BODY</span></p>
 </body>
</html>

% qh -hew sample.xml | page-gen >sample.c
% cat sample.c

#include "dvm2.h"
extern void replace(xml);

void generate(xml e) {
    x_begin("html");
      x_begin("head");
        x_begin("title");
          x_begin("span");
            x_pcdata("TITLE");
          x_end("span");
          replace(x_pop());
        x_end("title");
      x_end("head");
      x_begin("body");
        x_begin("p");
          x_begin("span");
            x_pcdata("BODY");
          x_end("span");
          replace(x_pop());
        x_end("p");
      x_end("body");
    x_end("html");
}

#ifdef TEST

int main(void) {
    generate(pcdata_str(""));
    write_xml(stdout, "", x_pop(), XML_SHOW_HTML|XML_SHOW_LATIN1);
    return 0;
}

#endif/*TEST*/

Now plug in a definition:

void replace(xml e) {
    char const *k = text_of(pcdata_text(e));
    if (0 == strcmp(k, "TITLE")) {
	x_pcdata("The title");
    } else
    if (0 == strcmp(k, "BODY")) {
	x_pcdata("The body");
    } else {
	x_begin1("font", "color", "red");
	  x_pcdata("No value known for: ");
	  x_push(e);
	x_end("font");
    }
}

and you're away laughing.

The idea here is that the input is turned into C code that
will reproduce it, except that elements with the attribute
class = "C:<<function>>" will be handed to the function of
the given name for processing.  The Erlang version would
translate

<html>
 <head>
  <title><span class="E:mod:replace">TITLE</span></title>
 </head>
 <body>
  <p><span class="E:mod:replace">BODY</span></p>
 </body>
</html>

to

f() ->
    {html,[],[
      {head,[],[
        {title,[],[
	  ]++mod:replace({span,[],[<<"TITLE">>]})++[
	  ]}]},
      {body,[],[
        {p,[],[
          ]++mod:replace({span,[],[<<"BODY">>]})++[
          ]}]}]).

This kind of stuff is _so_ easy to do...  (The C example is real;
the Erlang one is not.)