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71915d24b1
Add a way to specify a specific version from the command line by setting VERSION makefile's variable. Part of MB14-040.
65 lines
2.4 KiB
ReStructuredText
65 lines
2.4 KiB
ReStructuredText
.. _Introduction:
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************
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Introduction
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************
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The templates parser package has been designed to parse files and to
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replace some specific tags into these files by some specified values.
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The main goal was to ease the development of Web servers. In CGI
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(*Common Gateway Interface*) mode you have to write the HTML page in
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the program (in Ada or whatever other languages) by using some specific
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libraries or by using only basic output functions like Ada `Put_Line` for
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example. This is of course not mandatory but by lack of a good library
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every Web development end up doing just that.
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The main problems with this approach are:
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* It is painful to have to recompile the program each time you have
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a slight change to do in the design (center an image, change the border
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width of a table...)
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* You have the design and the program merged together. It means that
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to change the design you must know the Ada language. And to change the
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Ada program you need to understand what is going on with all these
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inline HTML command.
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* You can't use the nice tools to generate your HTML.
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With the templates parser package these problems are gone. The code and
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the design is **completely** separated. This is a very important
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point. PHP or JSP have tried this but most of the time you have the
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script embedded into the Web template. And worst you need to use another
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language just for your Web development.
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* The HTML page is separated from the program code. Then you can
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change the design without changing the code. Moreover when you fix the
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code you don't have to handle all the specific HTML output. And you do
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not risk to break the design.
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* It is easier to work on the design and the program at the same time
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using the right people for the job.
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* It reduces the number of *edit/build/test* cycles. Writing HTML
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code from a program is error prone.
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* It is possible to use standard tools to produce the HTML.
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* You don't have to learn a new language.
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* The script is Ada, so here you have the benefit of all the Ada power.
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In fact, the Ada program now simply computes some values, gets some data
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from a database or whatever and then calls the templates parser to output
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a page with the data displayed. To the templates parser you just pass
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the template file name and an associative table.
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It is even more convenient to have different displays with the same set
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of data. You just have to provide as many templates as you like.
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