documentclass{article}
usepackage{listofitems}
defposa(#1){%
    readlist*myarg{#1}
    if+myarg[1]Pluselse if-myarg[1]Minuselse Retry fifi
}
begin{document}

    posa(+)

    posa( -)

    posa(?)

    posa( + )

end{document}