nl_tokens: _v : validate argument n with fn name and message
pl_tokens: function _v ( fn , n , v , type ) { n = { 1 : 'first' , 2 : 'second' , 3 : 'third' , 4 : 'fourth' } [ n ] _a ( ! type || ( typeof v === type ) , fn , "" + <mask> + " expected for " + n + " argument" ) }