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cl-embwebtemplates

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This is an interesting templating library. The most interesting features are:

• named template pieces can call each other;
• debug mode allows to inspect generated code;
• different escape methods.

Here is how template functions can be reused:

POFTHEDAY> (cl-emb:register-emb "user"
            "<a href=\"/users/<% @var nickname %>\"><% @var name %></a>")

POFTHEDAY> (cl-emb:register-emb "user-list"
            "
<ul>
  <% @loop users %>
    <li><% @call user %></li>
  <% @endloop %>
</ul>
")

POFTHEDAY> (cl-emb:execute-emb "user-list"
             :env '(:users
                    ((:nickname "bob"
                      :name "Bob Hopkins")
                     (:nickname "alice"
                      :name "Alice Cooker"))))
"
<ul>
  
    <li><a href=\"/users/bob\">Bob Hopkins</a></li>
  
    <li><a href=\"/users/alice\">Alice Cooker</a></li>
  
</ul>
"

Let's see which code was generated for "user-list". To make this work, we'll need to set *debug* variable and recompile the template:

POFTHEDAY> (cl-emb:pprint-emb-function "user-list")

(LAMBDA
    (
     &KEY CL-EMB-INTERN::ENV CL-EMB-INTERN::GENERATOR-MAKER
     CL-EMB-INTERN::NAME)
  (DECLARE (IGNORABLE CL-EMB-INTERN::ENV CL-EMB-INTERN::GENERATOR-MAKER))
  (LET ((CL-EMB-INTERN::TOPENV CL-EMB-INTERN::ENV)
        (CL-EMB-INTERN::TEMPLATE-PATH-DEFAULT
         (IF (TYPEP CL-EMB-INTERN::NAME 'PATHNAME)
             CL-EMB-INTERN::NAME
             *DEFAULT-PATHNAME-DEFAULTS*)))
    (DECLARE
     (IGNORABLE CL-EMB-INTERN::TOPENV CL-EMB-INTERN::TEMPLATE-PATH-DEFAULT))
    (WITH-OUTPUT-TO-STRING (*STANDARD-OUTPUT*)
      (PROGN
       (WRITE-STRING "
<ul>
  ")
       (DOLIST
           (CL-EMB-INTERN::ENV
            (CL-EMB::AUTOFUNCALL (CL-EMB::GETF-EMB "users")))
         (WRITE-STRING "
    <li>")
         (FORMAT T "~A"
                 (LET ((CL-EMB:*ESCAPE-TYPE* CL-EMB:*ESCAPE-TYPE*))
                   (CL-EMB:EXECUTE-EMB "user" :ENV CL-EMB-INTERN::ENV
                                       :GENERATOR-MAKER
                                       CL-EMB-INTERN::GENERATOR-MAKER)))
         (WRITE-STRING "</li>
  "))
       (WRITE-STRING "
</ul>
")))))

As you can see, cl-emb generates a straight forward Lisp code.

Now let's check how fast cl-emb is and compare it to HTML template engines reviewed in previous days:

POFTHEDAY> (cl-emb:register-emb "render"
             "
<title><% @var title %></title>
<ul>
<% @loop items %><li><% @var value %></li><% @endloop %>
</ul>
")

POFTHEDAY> (time
            (loop repeat 1000000
                  do (cl-emb:execute-emb "render"
                       :env '(:title "Foo Bar"
                              :items ((:value "One")
                                      (:value "Two")
                                      (:value "Three"))))))
Evaluation took:
  1.436 seconds of real time
  1.441475 seconds of total run time (1.421158 user, 0.020317 system)
  [ Run times consist of 0.104 seconds GC time, and 1.338 seconds non-GC time. ]
  100.35% CPU
  3,172,183,256 processor cycles
  767,974,304 bytes consed

That is pretty fast. Slightly slower than Spinneret but faster than Zenekindarl.

To learn more about cl-emb's features, read it's docs!