[pstricks] Vector fields

[Hamed Al-Sulami]

Hi,

Guys can somebody explain for me the code of the following 

 

\SpecialCoor

 

\begin{pspicture}(-6,-6)(6,6)

  \psaxes{<->}(0,0)(-6,-6)(6,6)

  \psset{arrows=->}

  \multido{\ia=-5+1}{11}{%

    \multido{\ib=-5+1}{11}{%

      \pstVerb{/x \ia\space def

               /y \ib\space def

               y 0 eq

                 {/ValueTempA 0 def

                  /ValueTempB 0.5 def}

                 {/ValueTempZ 2 1 x x mul y y mul div add sqrt mul def

                  /ValueTempA 1 ValueTempZ div def

                  /ValueTempB x y ValueTempZ mul div def}

                 ifelse}

      \psline(! x ValueTempA sub y ValueTempB sub)

             (! x ValueTempA add y ValueTempB add)}}

\end{pspicture}

 

Because when I tried to imitate the above code for the vector fields
function <2x,y>  I got something different.

 

Thanks

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