nl_tokens: Finds the next edge with the minimum slack .
pl_tokens: function findMinSlack ( ) { var result , eSlack = Number . POSITIVE_INFINITY ; minLen . forEach ( function ( mle /* minLen entry */ ) { if ( remaining . has ( mle . u ) !== remaining . has ( mle . v ) ) { var mleSlack = rankUtil . slack ( g , mle . u , mle . v , mle . len ) ; if ( mleSlack < eSlack ) { if ( ! remaining . has ( mle . u ) ) { result = { treeNode : mle . u , graphNode : mle . v , len : mle . len , reversed : false , weight : mle . weight } ; } else { result = { treeNode : mle . v , graphNode : mle . u , len : - mle . len , reversed : <mask> , weight : mle . weight } ; } eSlack = mleSlack ; } } } ) ; return result ; }