%!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

/apush.right { % [a b] c -> [a b c]
    exch
    [ exch aload length 2 add -1 roll ]
} bind def


% end included library code

/straightline {
    0 dict begin
    /a exch def
    /b 0 array def
    a {
        /xy exch def
        /u true def
        b {
            /bxy exch def
            xy 0 get bxy 0 get eq xy 1 get bxy 1 get eq and {
                /u false def
                exit
            } if
        } forall
        u {
            /b b xy apush.right def
        } if
    } forall
    b length 3 lt {
        true
    } {
        true
        /p b 0 get 0 get def
        /q b 1 get 0 get b 0 get 0 get sub def
        /r b 0 get 1 get def
        /s b 1 get 1 get b 0 get 1 get sub def
        2 1 b length 1 sub {
            /tpair exch b exch get def
            q 0 eq tpair 0 get b 0 get 0 get ne and {
                pop false
                exit
            } if
            s 0 eq tpair 1 get b 0 get 1 get ne and {
                pop false
                exit
            } if
            q 0 ne s 0 ne and {
                tpair 0 get p sub q div
                tpair 1 get r sub s div
                ne {
                    pop false
                    exit
                } if
            } if
        } for
    } ifelse
    end
} bind def

(straightline) test.start
[[2 1] [2 3] [2 5]] straightline test
[[1 4] [3 4] [10 4]] straightline test
[[0 0] [1 1] [2 3]] straightline not test
[[1 1] [1 1] [1 1]] straightline test
test.end