Introduction

It was mentioned that students can quickly master the D programming language without a detailed study using mostly its subset, which is close to the C PL.

Consider a simple program that reads from a file of 10 lines, each containing a single number and prints to the standard output at the same number, but shifted to the mathematician expectation.

Whereas idiomatic D code looks pretty unusual:

import std.algorithm.iteration : map, each;
import std.array : array;
import std.conv : to;
import std.range : takeExactly, tee;
import std.stdio;

void main()
{
    double mean = 0;
    auto sample = File("10numbers.txt")
        .byLine
        .takeExactly(10)
        .map!(to!double)
        .tee!((x){mean += x;})
        .array;
    mean /= sample.length;
    // prints one element per line
    sample.map!(x => x - mean).each!writeln;
}

for many unfamiliar with the language D the same program can be implemented even as more complex, but at the same time more understandable way:

import std.stdio;

void main()
{
    File fin = File("10numbers.txt");
    double[] sample;
    sample.length = 10;
    double mean = 0;
    for(int i = 0; i < sample.length; i++)
    {
        fin.readf("%s", &sample[i]);
        if(!fin.eof)
            fin.readln();
        mean += sample[i];
    }
    mean /= sample.length;
    // prints one element per line
    for(int i = 0; i < sample.length; i++)
    {
        writeln(sample[i] - mean);
    }
}

The present documentation is submitted to the rapid introduction to D for those who are already somehow familiar with the C language and for some reasons do not want to waste time on a consistent study of the D language and related tools.

If you decide to use the D language in your daily work, you should start immediately with the study of the official page and of the book “The D Programming Language” by Andrei Alexandrescu.

Probably D is the most powerful of the present system programming languages.

D is a dragon [1]. Have a nice flight!

[1]	D is a dragon, or why D matters for Bioinformatics by Pjotr Prins.