gistfile1.txt

use nom::{double};

named! (pub comma,
        tag! (b","));

// Parse a viewBox attribute
// https://www.w3.org/TR/SVG/coords.html#ViewBoxAttribute
//
// viewBox: double [,] double [,] double [,] double [,]
//
// x, y, w, h
//
// Where w and h must be nonnegative.

named! (pub view_box<(f64, f64, f64, f64)>,
        verify! (ws! (do_parse! (x: double >>
                                 opt! (comma) >>
                                 y: double >>
                                 opt! (comma) >>
                                 w: double >>
                                 opt! (comma) >>
                                 h: double >>
                                 (x, y, w, h))),
                 |(x, y, w, h)| w >= 0.0 && h >= 0.0));


#[test]
fn parses_view_box () {
    assert_eq! (view_box (b"1 2 3 4"), IResult::Done (&b""[..], (1f64, 2f64, 3f64, 4f64)));
}

gives me

---- parsers::tests::parses_view_box stdout ----
	thread 'parsers::tests::parses_view_box' panicked at 'assertion failed: `(left == right)` (left: `Error(Position(Alt, [49, 32, 50, 32, 51, 32, 52]))`, right: `Done([], (1, 2, 3, 4))`)', parsers.rs:95