{
    print-nullterm 'H''e''l''l''o'' ''W''o''r''l''d''!''\n''\0';

    /*  test ratio
     */
    print-nullterm
        (fmt-ratio { 4; int-neg 3; })
        ' ''*'' '
        (fmt-ratio { 7; 4; })
        ' ''='' '
        (fmt-ratio (ratio-mul { 4; int-neg 3; } { 7; 4; }))
        '\n''\0';

    /* Colors
     */
    let red-u8rgb
        : <Fn <> Color ~ RGB ~ <Vec3 ℝ_0,1 ~ ℤ_256 ~ machine.UInt64>>
        = λ{} ↦ { 0; 0; 255; };

    let green-u8rgb = λ{} ↦ { 0; 255; 0; };
    let blue-u8rgb = λ{} ↦ { 255; 0; 0; };
    let yellow-u8rgb = λ{} ↦ { 0; 220; 220; };

    print-nullterm (fmt-vec3i (morph-rgb-to-hsv yellow-u8rgb)) '\n''\0';

    print-nullterm
        (fmt-vec3i green-u8rgb)
        ' ''+'' '
        (fmt-vec3i blue-u8rgb)
        ' ''='' '
        (fmt-vec3i (vec3i-add green-u8rgb blue-u8rgb))
        '\n''\0';

    uint-machine-to-posint 16 256;
}