code: function find_first(seq, pred, ctx) { var i
          pred = pred || not_nilp
          seq  = Object(seq)
  
          for (i = 0; i < size(seq); ++i)
              if (i in seq && pred.call(ctx, seq[i], i, seq))
                  return seq[i]
  
          return undefined
      }
docs: /// Function find_first //////////////////////////////////////////////////  (seq:Sequence[, pred:Fn][, ctx:Object]) ↦ *mixed*  Returns the first element of the sequence to pass the predicate function.  If the predicate is not given, the function will return the first non-null element from the sequence.  A context may be given as the last argument; if so, the predicate function will be called with the given object as the `[[this]]`.