Literate Programming

If you look at the source code of this page you will notice that there are no :import: directives. So no C++ code gets imported. Instead C++ code gets created from this document. It also creates and executes some gnuplot scripts.

So if you read the source code of this page think of it as a single entity. Don't distinguish between doc-file, C++ code, shell script, gnuplot script. Seeing things this way follows ideas from literate programming.

Producing some Data

The following C++ code will be used later to create data for plotting the \(\sin\) function. Note that the C++ code is not getting imported from some external source. Instead the C++ code is part of the document source. This is similar to how you would embed C++ listings in a \(\LaTeX\) file.

tutorial/sin.cc

#include <cmath>

#include <iostream>

const int N = 100;

int

main()

{

    for (int i=0; i<=N; ++i) {

        const double x = 2*M_PI*i/N;

        std::cout << x << " " << sin(x) << std::endl;

    }

}

Compile this code from the command line with

$shell> cd tutorial
$shell> clang++ -Wall -o sin sin.cc

and then execute it with

$shell> cd tutorial
$shell> ./sin > data

Note that the output of sin gets redirected into a file named data.

Plotting Data

We will plot the data with gnuplot. The following commands will executed by gnuplot:

tutorial/sin.gps

set terminal png

set output "sin.png"

plot "data" using 1:2 with lines

Simply call gnuplot from the terminal like that

$shell> cd tutorial
$shell> gnuplot sin.gps

This will produce an image named sin.png that looks like that:

Final Notes

Think of reading some magic book where everything you read actually happens. That's how doctool reads the pagesource.