[pstricks] Re: Hyperbolas

[Herbert Voss]

Jacques L'helgoualc'h wrote:
> Jacques L'helgoualc'h a écrit, lundi 7 février 2005, à 17:36 :
> [...] 
> Yet another improvement
> 
> \makeatletter
> \def\psthyperbola{\pst at object{psthyperbola}}
> \def\psthyperbola at i#1#2{%
>   \pst at killglue
>   \begingroup
>   \use at par
>   \psthyperbola at ii{#1}{#2}
>   \psthyperbola at ii{#1 neg}{#2}% second branch
>   \endgroup
> }
> \def\psthyperbola at ii#1#2{% a b
>   \addto at pscode{%
>     /a {#1} bind def
>     /b {#2} bind def
>     /d {2 1 t dup mul sub div} bind def}% d = 2/(1 - t^2)
>   \parametricplot{-.99}{.99}{%
>     a d 1 sub mul % (1 + t^2)/(1 - t^2) = -1 + 2/(1 - t^2)
>     b t d mul mul}
> }
> \makeatother
> 
> but d depends on t: I feel it should be (re)defined inside the
> parametricplot loop?

no, but your binds do not really make sense here

Herbert



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