[OT] Converting booleans to numbers

[Timon Gehr via Digitalmars-d-learn]

On 19.09.2017 23:17, nkm1 wrote:

...
OTOH, booleans converting to numbers is a very questionable feature. > I 
certainly have never seen any good use for it. ...

Actually, it is useful enough to have a Wikipedia page:
https://en.wikipedia.org/wiki/Iverson_bracket

Example of a good use:

void floodFill(dchar[][] data,dchar c,int i,int j) {
    void dfs(int a, int b) {
        if (a<0 || a >= data.length) return;
        if (b<0 || b >= data[a].length) return;
        if (data[a][b] == c) return;
        data[a][b] = c;
        foreach(i; 0 .. 4){
            dfs(a + (i==0) - (i==1),
                b + (i==2) - (i==3));
        }
    }
    dfs(i, j);
}

unittest {
    import std.algorithm, std.conv, std.array;
    auto data = ["###.####...##"d,
                 "#....#...#..."d,
                 "..#....##.###"d,
                 "##...###...##"d,
                 "####...#....."d,
                 "#.#.#.#.#.#.#"d,
                 "#####.#######"d]
        .map!(to!(dchar[])).array;
    floodFill(data, '#', 1, 1);
    assert(data==["#############"d,
                  "#############"d,
                  "#########.###"d,
                  "########...##"d,
                  "########....."d,
                  "#.#.###.#.#.#"d,
                  "#############"d]);
}