[pstricks] points as arguments

[Kari Eloranta]

I am afraid that I do not know how to pass points as arguments. I tried to define a macro

\newcommand{\vektori[3]}{
  \psline[arrowsize=.3,arrows=->,linecolor=black](#1)(#2)
  \uput[-90](B){$\vec{#3}$}
}

for drawing force vectors in physics.

When I try to call the macro with

\vektori{6,6}{5,5}{F}

I get the error message "missing number treated as zero". Would anybody be kind enough and teach me what it is I am missing here. I have tried to find information from several books and internet sources without any success.

Best regards,
  Kari

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Kari Eloranta
Ketunpolku 1
40400 Jyväskylä
Puh: +358 40 586 7654