Utop autocompletion on Yosemite Mac

Much as in this Stackoverflow question(http://stackoverflow.com/questions/28671507/autocompletion-in-utop), autocompletion does not seem to work well in utop on my Yosemite mac.
 

   The TAB key does produce the common prefix to all possible autocompletions.
  However, I cannot move inside the autocompletion bar.
 

 The documentation says I should use M-left and M-right (I assume "left" and "right" mean the left and right arrow on my keyboard ?) but ALT+(left arrow) or ALT+(right arrow) do nothing. An answer to the above question suggested using ESC in place of ALT, but on my machine this seems to work or not work randomly. 

 

   I also tried following the instructions at https://github.com/diml/utop#key-bindings https://github.com/diml/utop#key-bindings , put the newly created lambda-term-inputrc in my .opam/ directory, and opened a new utop, excepting then CTRL+(left arrow) and CTRL+(right arrow) to allow me to move inside the autocompletion bar.  But nothing had changed.
 

    Any help appreciated.