git clone ''

(ql:quickload :cl-emb)

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.

This is a mirror of

The primary development repository is in Monotone, this repository will receive just the automated snapshots.




(ql:quickload :cl-emb)

CL-EMB can also be installed manually with ASDF-INSTALL.


[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 here.

[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.

[function] PPRINT-EMB-FUNCTION name

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

[function] CLEAR-EMB name

Remove named emb code.

[function] CLEAR-EMB-ALL

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] *ESCAPE-TYPE*

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

[special variable] *FUNCTION-PACKAGE*

Package the emb function body gets interned to.

Default: (find-package :cl-emb-intern).

[special variable] *DEBUG*

Debugging mode if T. Default: NIL.

[special variable] *LOCKING-FUNCTION*

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.


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, @ifnotempty, @unless, @endunless, @var, @repeat, @endrepeat, @loop, @endloop, @include, @includevar, @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.

@ifnotempty works like @if but considers the empty string false.

@ifequal accepts two parameters interpreted as variable names. It works like @if but checks whether the values of two variables are equal. Variable names are intepreted as in @var.

Note that @ifnotempty and @ifequal are supposed to be used together with @else and @endif.

@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), latex.

@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 @endloop.

@include includes a given file. Relative to current template. @includevar does the same, but the parameter is treated like a variable name containing the path to the file. Variable name is treated like in @var.

@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, latex).

@genloop starts a special kind of loop: a generator loop. It must be terminated by @endgenloop and operates on a generator returned by the given GENERATOR-MAKER (see EXECUTE-EMB). The GENERATOR-MAKER gets called 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 (GETF (GETF (GETF ENV :FOO) :BAR) :QUUX).


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 and lsp-LICENSE.txt Thanks to Edi Weitz for letting me use his code for ESCAPE-FOR-XML.

Thanks to Eitarow Fukamachi for the whitespace-trimming patch.

Thanks to Christoph Finkensiep for making getf* a generic function.


Stefan Scholl

Current Maintainer

Michael Raskin