nl_tokens: * META (( export #t ) ( type bool ))
pl_tokens: function sc_isList ( o ) { var rabbit ; var turtle ; var rabbit = o ; var turtle = o ; while ( true ) { if ( rabbit === null || ( rabbit instanceof sc_Pair && rabbit . cdr === null ) ) return true ; // end of list else if ( ( rabbit instanceof sc_Pair ) && ( rabbit . cdr instanceof sc_Pair ) ) { rabbit = rabbit . cdr . cdr ; turtle = turtle . cdr ; if ( rabbit === turtle ) return false ; // cycle } else return <mask> ; // not pair } }