console 7 segment display

display7.d

import std.algorithm;
import std.array;
import std.conv;
import std.exception;
import std.stdio;
import std.string;
import std.traits;

alias Digit = bool[7];

template set(alias D, Args...) {
    static if (Args.length) {
        enum set = D.stringof ~ "[" ~ text(Args[0]) ~ "] = true;" ~ set!(D, Args[1 .. $]);
    } else {
        enum set = "";
    }
}

auto setDigit(ref Digit d, uint x) {
    assert(x >= 0 && x <= 10);
    d[] = false;

    final switch (x) {
        case 0: d[] = true; d[3] = false; break;
        case 1: mixin(set!(d, 2, 5)); break;
        case 2: mixin(set!(d, 0, 2, 3, 4, 6)); break;
        case 3: mixin(set!(d, 0, 2, 3, 5, 6)); break;
        case 4: mixin(set!(d, 1, 2, 3, 5)); break;
        case 5: mixin(set!(d, 0, 1, 3, 5, 6)); break;
        case 6: mixin(set!(d, 0, 1, 3, 4, 5, 6)); break;
        case 7: mixin(set!(d, 0, 2, 5)); break;
        case 8: d[] = true; break;
        case 9: mixin(set!(d, 0, 1, 2, 3, 5, 6)); break;
    }
}

auto loadDigits(string str)
{
    auto len = str.length;
    uint val = 0;
    try {
        val = to!uint(str);
    } catch (Exception e) {
        writefln("not able to parse %s as an unsigned integer");
        return;
    }

    auto digits = new Digit[len];
    foreach (i; 0 .. len) {
        setDigit(digits[i], str[i] - '0');
    }

    display(digits);
}

auto times(ulong n, lazy void fn)
{
    while (n--) fn();
}

auto display(Digit[] digits)
{
    auto len = to!int(digits.length);

    auto d = digits[$ - 1];
    (digits.length - 1).times(write(" "));
    write(d[0]? "/" : " ");
    writeln(d[2]? `\ ` : "  ");
    (digits.length - 1).times(write(" "));
    write(d[1]? `\` : " ");
    write(d[3]? `/` : " ");
    writeln(d[5]? `\` : " ");


    for (int i = len - 2; i >= 0; --i) {
        d = digits[i];
        i.times(write(" "));
        write(d[0]? "/" : " ");
        write(d[2]? `\` : " ");
        auto p = digits[i+1];
        write(p[4]? `\` : " ");
        writeln(p[6]? `/` : " ");

        i.times(write(" "));
        write(d[1]? `\` : " ");
        write(d[3]? `/` : " ");
        writeln(d[5]? `\` : " ");
    }

    d = digits[0];
    write(" ");
    write(d[4]? `\` : " ");
    writeln(d[6]? `/` : " ");

}

auto displayLeveled(Digit[] digits)
{
    // top row
    foreach (d; digits) {
        write((d[0])? " _ ": "   ");
    }
    writeln();

    foreach (d; digits) {
        write((d[1])? "|": " ");
        write((d[3])? "_": " ");
        write((d[2])? "|": " ");
    }
    writeln();

    foreach (d; digits) {
        write((d[4])? "|": " ");
        write((d[6])? "_": " ");
        write((d[5])? "|": " ");
    }
    writeln();
    writeln();
}

void main(string[] args) {

    string str;
    if (args.length >= 2) {
        str = args[1];
    } else {
        write("enter a positive integer: ");
        str = readln.strip;
    }

    loadDigits(str);
}