\header {

  texidoc = "Setting @code{positions} overrides the automatic
positioning of the slur. It selects the slur configuration closest to
the given pair. "
  
  }
\version "2.19.21"

\paper { ragged-right = ##T }
\relative {
  \override Slur.positions = #'(-4 . -5)
  e'( f g)
}