nl_tokens: Given array and fun returns an array of rose trees where each tree s root is the element and its children are fun ( element ) . [ a ] - > ( a - > [ a ] ) - > RoseTree a
pl_tokens: function arrayToRoseTrees ( array , fun ) { return array . <mask> ( function ( element ) { return new RoseTree ( element , function ( ) { return fun ( element ) ; } ) ; } ) ; }