// Slices are an important data type in Chapel, giving
// a more powerful interface to sequences than arrays.

use IO;

proc main() {
    // Unlike arrays, slices in Chapel are created using the 'new' keyword
    // and are of type 'domain'. An uninitialized domain is empty.
    var s: domain(1) = {1..0};
    writeln("uninit: ", s, " ", s.size == 0, " ", s.size == 0);

    // To create an empty domain with non-zero size, we can specify a range.
    // Here we create a domain of size 3.
    s = {1..3};
    writeln("emp: ", s, " len: ", s.size, " cap: ", s.size);

    // We can set and get elements using array notation.
    var a: [s] string;
    a[1] = "a";
    a[2] = "b";
    a[3] = "c";
    writeln("set: ", a);
    writeln("get: ", a[3]);

    // 'size' returns the length of the domain as expected.
    writeln("len: ", s.size);

    // To add elements to a domain, we can use the '+=' operator.
    s += 4..5;
    a[4] = "d";
    a[5] = "e";
    writeln("apd: ", a);

    // Domains can be copied. Here we create a new domain 'c' of the same size as 's'.
    var c = s;
    var b: [c] string = a;
    writeln("cpy: ", b);

    // Domains support slicing with the syntax domain[low..high].
    var l = s[3..5];
    writeln("sl1: ", a[l]);

    // This slices up to (but excluding) index 5.
    l = s[1..4];
    writeln("sl2: ", a[l]);

    // And this slices from index 3 to the end.
    l = s[3..];
    writeln("sl3: ", a[l]);

    // We can declare and initialize a domain and its associated array in a single line.
    var t = {1..3};
    var tArr: [t] string = ["g", "h", "i"];
    writeln("dcl: ", tArr);

    // Chapel doesn't have a built-in 'slices' module, but we can compare arrays directly.
    var t2 = {1..3};
    var t2Arr: [t2] string = ["g", "h", "i"];
    if tArr == t2Arr then
        writeln("t == t2");

    // Domains can be multi-dimensional. The size of inner domains can vary.
    var twoD: [1..3] domain(1);
    for i in 1..3 {
        twoD[i] = {1..i};
    }
    var twoDArr: [1..3] [twoD[1..3]] int;
    for i in 1..3 {
        for j in 1..i {
            twoDArr[i][j] = i + j - 1;
        }
    }
    writeln("2d: ", twoDArr);
}