Raul, your versions have nice features, but they don't seem to handle
the problem of a=b or c=d.
>
> trap=: 1 : 0
> 'a b c d'=. m
> s=. % _1 1 * _2 -/\ m
> z=. - 0 3 { m
> 1 <. 0 >. [: <./ s * z +/ ]
> )
>
> However, if that first line annoys you too much, an
> equivalent form would be:
>
> trap=: 1 : 0
> s=. % _2 -/\ m * _1 _1 1 1
> z=. - 0 3 { m
> 1 <. 0 >. [: <./ s * z +/ ]
> )
>
> Finally, note that these implementation of trap support treatment
> of multiple "trapezoids" at the same time:
>
> (2 6 8 10,. 3 5 7 9) trapa i. 11
> 0 0 0 0.25 0.5 0.75 1 1 1 0.5 0
> 0 0 0 0 0.5 1 1 1 0.5 0 0
>
> FYI,
>
> --
> Raul
>
--
(B=)
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