generates a random string from stdin text input using a Nth order markov chain

markov1.d

import std.stdio, std.array, std.string, std.conv, std.random;

enum { ORDER = 2, MAX_RESULT_WORDS = 20 }

void main()
{
    uint[string][string] dict;
    string[] prev;
    foreach (line; stdin.byLine())
        foreach (word; split(to!string(toLower(line))))
        {
            if (prev.length == ORDER)
                ++dict[join(prev, " ")][word];
            prev ~= word;
            if (prev.length > ORDER)
                prev.popFront();
        }

    auto state = dict.keys[uniform(0, dict.length)];
    auto result = split(state);
    for (int i = MAX_RESULT_WORDS; i && state in dict; --i)
    {
        auto word = dict[state].keys[dice(dict[state].values)];
        result ~= word;
        state = join(result[$-ORDER .. $], " ");
    }
    writeln(join(result, " "));
}