%!PS

% begin included library code
% see https://codeberg.org/Firedrake/postscript-libraries/
/test {
    /test.count test.count 1 add def
    {
        /test.pass test.pass 1 add def
    } {
        ( ) print
        test.count (....) cvs print
        (-fail) print
    } ifelse
} bind def

/test.end {
    ( ) print
    test.count 0 gt {
        (Passed ) print
        test.pass (...) cvs print
        (/) print
        test.count (...) cvs print
        ( \() print
        test.pass 100 mul test.count idiv (...) cvs print
        (%\)) print
        (\r\n) print
    } if
} bind def

/test.start {
    print (:) print
    /test.pass 0 def
    /test.count 0 def
} bind def


% end included library code

/productsign {
    1 exch
    {
        dup 0 lt {
            pop neg
        } {
            0 eq {
                pop 0
                exit
            } if
        } ifelse
    } forall
} bind def

(productsign) test.start
[-1 -2 -3 -4 3 2 1] productsign 1 eq test
[1 2 0 -2 -1] productsign 0 eq test
[-1 -1 1 -1 2] productsign -1 eq test
test.end