Make unix representation more efficient
Make unix representation more efficient

By not allocation a closure on every update

janestreet/jbuilder,janestreet/jbuilder,janestreet/jbuilder,dra27/jbuilder,janestreet/jbuilder,dra27/jbuilder,janestreet/jbuilder,dra27/jbuilder,janestreet/jbuilder,dra27/jbuilder,dra27/jbuilder,rdavison/jbuilder,dra27/jbuilder,rdavison/jbuilder