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Guile Web Programming Library

This document describes Guile-Web by Clinton Ebadi

This document applies to version 0.5.0 of the library named Guile-Web

Copyright 2003,2004,2005 Clinton Ebadi

Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.1 or any later version published by the Free Software Foundation; with no Invariant Sections, with no Front-Cover Texts, and with no Back-Cover Texts.

1. Introduction  
2. Hash-Dash reader extension  
3. Session Management  
4. Object Serialization  
5. Miscellaneous Database Tools  
6. XHtml Generation  
7. Page Templates  
A. GNU Free Documentation License  

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1. Introduction

Guile-web is a set of modules for Guile Scheme intended to make programming web applications in Guile easier. Guile-web is not intended to be used alone; rather as a supplement to guile-www (see section `Guile-WWW Manual' in Guile-WWW). Guile-web adds higher level concepts like session management to Scheme web programming.

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2. Hash-Dash reader extension

(web hash-dash) Module

Scripts often time need to echo large amounts of static html. Doing this with Scheme display is extremely tedious, so guile-web provides the #- reader extension to do this. To use it you put a #- followed by as many lines of text as you want with a -# at the end of the text block. This reader extension will return the text block as a string. For example:

;;; output page header
(define (header title)
(for-each display
    <?xml version="1.0" encoding="utf-8"?>
    <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN"
    <html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en">
        <title>-# title #-</title>
(header "foobar")

That will create a xhtml 1.0 header.

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3. Session Management

(web session) Module

Session Management is a powerful tool that makes web programming much easier if you are doing authentication. I won't go into the details of what a session is here, look on Google for that (or send me an email telling me to put a blurb on it here if you really want it in the manual). You must call session:start before you output any other headers. You also must call session:save before you exit your script or else ALL changes to the session will be LOST.

An easy way to to ensure that the session is saved if you are using scripts that execute and exit is to add session:save to the exit-hook hook.

(add-hook! exit-hook session:save)

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4. Object Serialization

(web serialize) Module

When you serialize an object you transform the object into a representation suitable for storing in a file (usually). The serialize module exports several functions for serializing and unserializing GOOPS objects. Note that every SMOB has a GOOPS class associated with it once GOOPS is loaded (?).

Note that this module is really meant for internal usage by the session mananger, but since you have to add your own serializers for user defined types, I figured I may as well may the entire API public (someone might find it useful).

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5. Miscellaneous Database Tools

(web db) Module

These are only useful if you are using SimpleSQL, available from http://guile-simplesql.sourceforge.net/. (Maybe this module will be merged into it). The problem with simplesql is that it returns a list of vectors that is very difficult to use. This module defines a set of procedures that converts the result of a simplesql-query into a much nicer form. We will call this data type an assoc.

If you would like to iterate over the result you can use array-for-each and array-map (or any of the other array functions) because a vector is simply an array of rank 1. I decided to use a vector instead of a list for this because it is more efficient for this (e.g. the result is constant, the number of rows may be very large and accessing a large numbered row is constant time for the vector and O(N) time for a list, etc.).

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6. XHtml Generation

(web xhtml) Module

Being able to generate correct HTML is a useful thing, so I have written a set of procedures for generating xhtml 1.0 documents. Note that correctness isn't entirely forced; you can, for example, put an inline element in a place where only a block level element is valid; but it does make generating a xhtml document somewhat easier.

There are two ways to use the html module: with the global instance or by specifying your own instance. If you use your own object, you must make a <html-document>, which takes these keyword arguments:

#:attributes is a list of lists that specify the default values for all tag attributes, e.g. ((style "special style") (class "magic")).

To display data generated by the various tag procedures, you use xhtml:print. If the first argument is a <html-document> all of the tags will output using the default port for that object and use the default attribute values for that object as well. If the first argument is not a <html-document>, then the expressions will be printed to the output port of the global <html-document> which is the (current-output-port) of the dynamic root you are in (there is also one global <html-document> per dynamic root).

All tags have a producedure named xhtml:tagname. If the tag is non-empty, this may tag any number of forms to be printed inside of the tag as arguments, including other tags. Also is the tag is non-empty, there are -start and -end procedures defined to spit out the start and end tags of the tag. If a tag is empty, it may not contain any other data. All tags take an optinal #:atts keyword argument that contains a list of lists that specify the attributes for the tag in the form ((attribute-name-as-a-symbol "attribute value in a string") ...). The start tag also supports this, the end tag doesn't. You must print the output of all the tag function with xhtml:print.

All documents should begin with a call to xhtml:dtd which returns the DTD for the document. Its #:atts argument takes one member: encoding which is the encoding of the document. This defaults to "iso-8859-1".

Available tags:

An example:

(use-modules (web html)
	     (web hash-dash))

(display "Content-Type: text/html\r\n\r\n")
(force-output (current-output-port))


  (xhtml:title "MOO")))

 (xhtml:h1 "tra la la!")
  #- Moo moo moooooooooo. I am so cool.
     Multiple lines are so great.
     All will fear my elite! -#
     #- This is where the second line begins. -#)

There is another procedure, xhtml:tag-tree->shtml tag which accepts a tag as its argument and return the tag tree in shtml (a subset of SXML used by HtmlPrag).

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7. Page Templates

(web template) Module

Languages like PHP allow one to embed code within a document. The solution used by PHP isn't really optimal; guile-web uses a slightly better method of page templates. A page template is just a document with a bit of special formatting to make calls to various template procedures. This is somewhat similar to Perl's Mason module but is currently much more limited.

Scheme procedures:

To make a template call from a template, you encase the call in square brackets ([ and ]). The call is merely a procedure call that is expected to return some data that is substituted into the page at that point. If a double [[ is found it will be inserted into the output stream as a single [; a double ]] can be used inside of a template call to pass a literal ] to the procedure.

An example script that parses a page:

;;; page.scm
(use-modules (web template))

   ;; open template 
   (my-file (open-input-file "page.tmpl"))

   ;; Create a command table
   (my-procs (make-hash-table 10))
   ;; Output port
   (page-out (open-output-file "page.out")))

  ;; Initialize command table
  (hash-set! my-procs 'comment
             (lambda args ""))

  (hash-set! my-procs 'cool
             (lambda (who)
                     (string-append who "is cool")))

  (hash-set! my-procs 'add +)

  ;; Parse page and write it to page.out
  (for-each (lambda (x) (display x page-out))
            (template:parse my-procs my-file))
  (close-port page-out))

The page used by the script:

[comment page.tmpl]
Tra la la!
[[This will be inside of square brackets]
2 + 2 = [add 2 2]. I think that [cool Clinton]! He has a Camaro and
wrote Guile-Web so he deserves mad props. 

Only he's not a hip-hop kid so he doesn't think that 2 + 2 = [add 2 3]
or anything. Yeah. Also, this example really isn't that great.
[comment Since comment is a multi-argument procedure, I can put
whatever I want in here as long as it is a valid piece of Scheme data.]

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A. GNU Free Documentation License

Version 1.2, November 2002

Copyright © 2000,2001,2002 Free Software Foundation, Inc.
59 Temple Place, Suite 330, Boston, MA  02111-1307, USA

Everyone is permitted to copy and distribute verbatim copies
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A.0.1 ADDENDUM: How to use this License for your documents

To use this License in a document you have written, include a copy of the License in the document and put the following copyright and license notices just after the title page:

  Copyright (C)  year  your name.
  Permission is granted to copy, distribute and/or modify this document
  under the terms of the GNU Free Documentation License, Version 1.2
  or any later version published by the Free Software Foundation;
  with no Invariant Sections, no Front-Cover Texts, and no Back-Cover
  Texts.  A copy of the license is included in the section entitled ``GNU
  Free Documentation License''.

If you have Invariant Sections, Front-Cover Texts and Back-Cover Texts, replace the "with...Texts." line with this:

    with the Invariant Sections being list their titles, with
    the Front-Cover Texts being list, and with the Back-Cover Texts
    being list.

If you have Invariant Sections without Cover Texts, or some other combination of the three, merge those two alternatives to suit the situation.

If your document contains nontrivial examples of program code, we recommend releasing these examples in parallel under your choice of free software license, such as the GNU General Public License, to permit their use in free software.

[Top] [Contents] [Index] [ ? ]

Table of Contents

1. Introduction
2. Hash-Dash reader extension
3. Session Management
4. Object Serialization
5. Miscellaneous Database Tools
6. XHtml Generation
7. Page Templates
A. GNU Free Documentation License
A.0.1 ADDENDUM: How to use this License for your documents

[Top] [Contents] [Index] [ ? ]

Short Table of Contents

1. Introduction
2. Hash-Dash reader extension
3. Session Management
4. Object Serialization
5. Miscellaneous Database Tools
6. XHtml Generation
7. Page Templates
A. GNU Free Documentation License

[Top] [Contents] [Index] [ ? ]

About this document

This document was generated by using texi2html

The buttons in the navigation panels have the following meaning:

Button Name Go to From 1.2.3 go to
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This document was generated by Clinton Ebadi on May, 14 2005 using texi2html