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========  --------------------
 CL-EMB   Embedded Common Lisp
========  --------------------

A mixture of features from eRuby and HTML::Template. You could name
it "Yet Another LSP" (LispServer Pages) but it's a bit more than that
and not limited to a certain server or text format.



CL-EMB can be installed with ASDF-INSTALL.
See http://weitz.de/asdf-install/ for further information.


[generic function]
EXECUTE-EMB name &key env generator-maker => string

  NAME can be a registered (with REGISTER-EMB) emb code or a pathname
  (type PATHNAME) of a file containing the code. Returns a string.
  Keyword parameter ENV to pass objects to the code. ENV must be a
  plist. ENV can be accessed within your emb code.
  The GENERATOR-MAKER is a function which gets called with a key and value
  from the given ENV and should return a generator function like described on

[generic function]
REGISTER-EMB name code => emb-function

  Internally registeres given CODE with NAME to be called with
  EXECUTE-EMB. CODE can be a string or a pathname (type PATHNAME) of
  a file containing the code.


  DEBUG function. Pretty prints function form, if *DEBUG* was T
  when the function was registered.

  Remove named emb code.

  Remove all registered emb code.

  Remove all registered file emb code (registered/executed by a pathname).

[special variable]
*EMB-START-MARKER* (default "<%")

  Start of scriptlet or expression. Remember that a following #\=
  indicates an expression.

[special variable]
*EMB-END-MARKER* (default "%>")
  End of scriptlet or expression.

[special variable]

  Default value for escaping @var output is :RAW
  Can be changed to :XML, :HTML, :URI, :URL, :URL-ENCODE

[special variable]

  Package the emb function body gets interned to.
  Default: (find-package :cl-emb-intern)

[special variable]

  Debugging mode if T. Default: NIL

[special variable]

  Function to call to lock access to an internal hash table.
  Must accept a function designator which must be called with
  the lock hold.
  IMPORTANT: The locking function must return the value of
  the function it calls!

        (defvar *emb-lock* (kmrcl::make-lock "emb-lock")
          "Lock for CL-EMB.")

        (defun emb-lock-function (func)
          "Lock function for CL-EMB."
          (kmrcl::with-lock-held (*emb-lock*)
            (funcall func)))

        (setf emb:*locking-function* 'emb-lock-function)

Files get cached and reread when they change.

The emb code consists of normal text (HTML, XML, or any other text
format) and special tags you know from eRuby or JSP (JavaServer Pages)
which can hold Common Lisp or CL-EMB's template tags, perhaps
comparable to JSP's taglib.

<% ... %>   is a scriptlet tag, and wraps
            Common Lisp code.

<%= ... %>  is an expression tag. Its content gets evaluated and fed as
            a parameter to (FORMAT T "~A" ...).

<%# ... #%> is a comment. Everything within will be removed/ignored.
            Can't be nested!


CL-USER> (asdf:oos 'asdf:load-op :cl-emb)
CL-USER> (cl-emb:register-emb "test1"
                              "10 stars: <% (dotimes (i 10) %>*<% ) %>")
CL-USER> (cl-emb:execute-emb "test1")
"10 stars: **********"

CL-USER> (cl-emb:register-emb "test2" "2 + 2 = <%= (+ 2 2) %>")
CL-USER> (cl-emb:execute-emb "test2")
"2 + 2 = 4"

CL-USER> (let ((emb:*emb-start-marker* "<?emb")
               (emb:*emb-end-marker* "?>"))
           (emb:register-emb "marker-test"
                             "42 + 42 = <?emb= (+ 42 42) ?>"))
CL-USER> (emb:execute-emb "marker-test")
"42 + 42 = 84"

Template Tags

You can use special template tags instead of Common Lisp code between
<% and %>. This will be translated to Common Lisp and serves as a
simple shortcut for you.

And more important: It's easier to use for non-programmers. A designer
can work on HTML code and insert these simple template tags.

Template tags start with @.

Currently supported:
@if, @else, @endif, @unless, @endunless, @var, @repeat, @endrepeat,
@loop, @endloop, @include, @call, @with, @endwith, @set, @genloop,
@endgenloop, @insert

@if and @unless check if the given parameter is set in the
supplied environment (parameter ENV of EXECUTE-EMB). The
environment is a plist with keyword + value pairs. Must be terminated
with @endif or @endunless.

@var emits the corresponding value from the environment. Uses the
escape type defined in *ESCAPE-TYPE* (Default :raw, no escaping) or
with -escape modifier. E. g. <% @var foo -escape xml %>
or without modifier <% @var foo %>
Supported escaping: raw, xml (aka html), uri (aka url or url-encode)

@insert inserts a given (text) file. Parameter from the environment.
E. g. <% @insert textfile %>

@repeat repeats everything between it and @endrepeat the given times.
Parameter can be a number or a name. The name will be used to lookup
the corresponding value from the environment.

@loop loops over a named list in the environment. Environment
gets set to current plist inside this list. Must be terminated with

@include includes a given file. Relative to current template.

@call calls a given emb-function, which was registered with REGISTER-EMB

@with is similar to @loop as it sets the current environment to the named
plist. @loop needs a list of plists and @with just a plist associated to
the given name. Block ends in @endwith.

@set is used to set special variables like *ESCAPE-TYPE* from within a
emb code. This way a default for a file can be specified in the file
itself. The variables are changed for the current and called/included code.
Changes to the variables in called/included code don't effect the caller/
includer. E. g. <% @set escape=uri %>
Currently supported: escape (raw, xml, html, url, uri, url-encode)

@genloop starts a special kind of loop: a generator loop. It must be
terminated by @endgenloop and operates on a generator returned by the 
with two parameters: the key (which is the argument to @genloop) and the
corresponding value in the plist. Each time in the loop the generator is
called first with the parameter :TEST to see if there's data left.
The generator must return a plist on :NEXT, which will be the current
ENV (like @with or within a normal @loop).

The parameters which access the environment can just be the name of a
keyword symbol in the plist. foo -> :FOO in (:FOO "bar")
Or you can provide a path within a nested plist structure by dividing the
parts of the path with a slash. foo/bar -> Value of :BAR inside the
plist at :FOO. (:FOO (:BAR "yeah")) -> "yeah"
Starting the parameter with a slash lets it traverse the nested plists
from the top. That way you can access top values inside loops.

Writing "<% @var foo/bar/quux %>" can be translated to


CL-USER> (cl-emb:register-emb "test1"
                              "Foo: <% @if foo %>Yes!<% @else %>No!<% @endif %>")
CL-USER> (cl-emb:execute-emb "test1" :env '(:foo t))
"Foo: Yes!"
CL-USER> (cl-emb:execute-emb "test1")
"Foo: No!"
CL-USER> (cl-emb:execute-emb "test1" :env '(:foo nil))
"Foo: No!"

CL-USER> (cl-emb:register-emb "test2"
                              "What is set? -> <% @call test1 %>")
CL-USER> (cl-emb:execute-emb "test2" :env '(:foo t))
"What is set? -> Foo: Yes!"

CL-USER> (cl-emb:register-emb "test3"
                              "10 stars: <% @repeat 10 %>*<% @endrepeat %>")
CL-USER> (cl-emb:execute-emb "test3")
"10 stars: **********"

CL-USER> (cl-emb:register-emb "test4"
                              "<% @loop numbers %>[<% @var de %>,<% @var en %>]<% @endloop %>")
CL-USER> (cl-emb:execute-emb "test4"
                             :env '(:numbers ((:de "EINS" :en "ONE")
                                              (:de "ZWEI" :en "TWO"))))

CL-USER> (emb:register-emb "test5"
                           "<a href=\"http://somewhere.test/test.cgi?<% @var foo -escape uri %>\"><% @var foo %></a>")
CL-USER> (let ((emb:*escape-type* :html))
           (emb:execute-emb "test5" :env '(:foo "10 > 7")))
"<a href=\"http://somewhere.test/test.cgi?10+%3E+7\">10 &gt; 7</a>"

CL-USER> (emb:register-emb "test6" "1. <% @with one %>BAZ: <% @var baz %><% @endwith%>
2. <% @with two %>BAZ: <% @var baz %><% @endwith%>")
CL-USER> (emb:execute-emb "test6" :env '(:one (:baz "first") 
                                         :two (:baz "second")))
"1. BAZ: first
2. BAZ: second"

CL-USER> (emb:register-emb "test7" " - <% @var foo -escape uri %> - ")
CL-USER> (emb:pprint-emb-function "test7")

     (WRITE-STRING " - ")
     (WRITE-STRING " - "))))
; No value

CL-USER> (emb:register-emb "test8" "<% @set escape=xml %>--<% @var hey %>--")
CL-USER> (emb:register-emb "test9" "--<% @var hey %>--<% @call test8 %>--<% @var hey %>--")
CL-USER> (emb:execute-emb "test9" :env '(:hey "5>2"))

CL-USER> (emb:register-emb "test10" "Square root from 1 to <% @var numbers %>: <% @genloop numbers %>sqrt(<% @var number %>) = <% @var sqrt %>  <% @endgenloop %>")
CL-USER> (defun make-sqrt-1-to-n-gen (key n)
           (declare (ignore key))
           (let ((i 1))
             #'(lambda (cmd)
                 (ecase cmd
                   (:test (> i n))
                   (:get `(:number ,i :sqrt ,(sqrt i)))
                   (:next (prog1 `(:number ,i :sqrt ,(sqrt i))
                            (unless (> i n)
                              (incf i))))))))
CL-USER> (emb:execute-emb "test10" :env '(:numbers 10) :generator-maker 'make-sqrt-1-to-n-gen)
"Square root from 1 to 10: sqrt(1) = 1.0  sqrt(2) = 1.4142135  sqrt(3) = 1.7320508  sqrt(4) = 2.0  sqrt(5) = 2.236068  sqrt(6) = 2.4494898  sqrt(7) = 2.6457512  sqrt(8) = 2.828427  sqrt(9) = 3.0  sqrt(10) = 3.1622777  "

CL-USER> (emb:register-emb "test11" "<% @loop bands %>Band: <% @var band %> (Genre: <% @var /genre %>)<br><% @endloop %>")
CL-USER> (emb:execute-emb "test11" :env '(:genre "Rock" :bands ((:band "Queen") (:band "The Rolling Stones") (:band "ZZ Top"))))
"Band: Queen (Genre: Rock)<br>Band: The Rolling Stones (Genre: Rock)<br>Band: ZZ Top (Genre: Rock)<br>"

CL-USER> (emb:register-emb "test12" "<% @repeat /foo/bar/count %>*<% @endrepeat %>")
CL-USER> (emb:execute-emb "test12" :env '(:foo (:bar (:count 42))))

CL-USER> (emb:register-emb "test13" "The file:<pre><% @insert textfile %></pre>")
#<CL-EMB::EMB-FUNCTION {5894326D}>
CL-USER> (emb:execute-emb "test13" :env '(:textfile "/etc/gentoo-release"))
"The file:<pre>Gentoo Base System version 1.6.14

Uses code from John Wiseman. See http://lemonodor.com/archives/000128.html
and lsp-LICENSE.txt
Thanks to Edi Weitz for letting me use his code for ESCAPE-FOR-XML.

Stefan Scholl <stesch@no-spoon.de>