D Programming Language 2.0

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Last update Thu Oct 1 22:59:52 2009

# Embedding D in HTML

The D compiler is designed to be able to extract and compile D code embedded within HTML files. This capability means that D code can be written to be displayed within a browser utilizing the full formatting and display capability of HTML.

For example, it is possible to make all uses of a class name actually be hyperlinks to where the class is defined. There's nothing new to learn for the person browsing the code, he just uses the normal features of an HTML browser. Strings can be displayed in green, comments in red, and keywords in boldface, for one possibility. It is even possible to embed pictures in the code, as normal HTML image tags.

Embedding D in HTML makes it possible to put the documentation for code and the code itself all together in one file. It is no longer necessary to relegate documentation in comments, to be extracted later by a tech writer. The code and the documentation for it can be maintained simultaneously, with no duplication of effort.

How it works is straightforward. If the source file to the compiler ends in .htm or .html, the code is assumed to be embedded in HTML. The source is then preprocessed by stripping all text outside of <code> and </code> tags. Then, all other HTML tags are stripped, and embedded character encodings are converted to ASCII. The processing does not attempt to diagnose errors in the HTML itself. All newlines in the original HTML remain in their corresponding positions in the preprocessed text, so the debug line numbers remain consistent. The resulting text is then fed to the D compiler.

Here's an example of the D program "hello world" embedded in this very HTML file. This file can be compiled and run.

    import std.stdio;

    int main()
    {
     writefln("hello world");
     return 0;
    }

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