# Revision history [back]

### connected sum of knots

Hi! I was trying to recursively construct connected sums of knots, but I seem to run in to some problems when connect summing a knot to itself more than two times:

B = BraidGroup(2)

trefoil = Knot(B([1,1,1]))

K = trefoil.connected_sum(trefoil)

L = K.connected_sum(trefoil)

This does not work:

ValueError                                Traceback (most recent call last)

ipython-input-1-7b977cf99468 in module()

2 trefoil = Knot(B([Integer(1),Integer(1),Integer(1)]))

3 K = trefoil.connected_sum(trefoil)

--> 4 L = K.connected_sum(trefoil)

/home/sc_serv/sage/local/lib/python2.7/site-packages/sage/knots/knot.pyc in connected_sum(self, other)

294         return Knot(B(list(b1.Tietze())

295                       + [(abs(i) + b2s) * Integer(i).sign() for i in b2.Tietze()]

--> 296                       + [b1s]))

297

/home/sc_serv/sage/local/lib/python2.7/site-packages/sage/knots/knot.pyc in __init__(self, data, check)

104         if check:

105             if self.number_of_components() != 1:

--> 106                 raise ValueError("the input has more than 1 connected component")

107

108     def __repr__(self):

ValueError: the input has more than 1 connected component


Am I doing something wrong here? Thanks in advance!

 2 retagged slelievre 16999 ●21 ●151 ●335 http://carva.org/samue...

### connected sum of knots

Hi! I was trying to recursively construct connected sums of knots, but I seem to run in to some problems when connect summing a knot to itself more than two times:

B = BraidGroup(2)

trefoil = Knot(B([1,1,1]))

K = trefoil.connected_sum(trefoil)

L = K.connected_sum(trefoil)

This does not work:

ValueError                                Traceback (most recent call last)

ipython-input-1-7b977cf99468 in module()

2 trefoil = Knot(B([Integer(1),Integer(1),Integer(1)]))

3 K = trefoil.connected_sum(trefoil)

--> 4 L = K.connected_sum(trefoil)

/home/sc_serv/sage/local/lib/python2.7/site-packages/sage/knots/knot.pyc in connected_sum(self, other)

294         return Knot(B(list(b1.Tietze())

295                       + [(abs(i) + b2s) * Integer(i).sign() for i in b2.Tietze()]

--> 296                       + [b1s]))

297

/home/sc_serv/sage/local/lib/python2.7/site-packages/sage/knots/knot.pyc in __init__(self, data, check)

104         if check:

105             if self.number_of_components() != 1:

--> 106                 raise ValueError("the input has more than 1 connected component")

107

108     def __repr__(self):

ValueError: the input has more than 1 connected component


Am I doing something wrong here? Thanks in advance!

 3 retagged tmonteil 27163 ●31 ●197 ●511 http://wiki.sagemath.o...

### connected sum of knots

Hi! I was trying to recursively construct connected sums of knots, but I seem to run in to some problems when connect summing a knot to itself more than two times:

B = BraidGroup(2)

trefoil = Knot(B([1,1,1]))

K = trefoil.connected_sum(trefoil)

L = K.connected_sum(trefoil)

This does not work:

ValueError                                Traceback (most recent call last)

ipython-input-1-7b977cf99468 in module()

2 trefoil = Knot(B([Integer(1),Integer(1),Integer(1)]))

3 K = trefoil.connected_sum(trefoil)

--> 4 L = K.connected_sum(trefoil)

/home/sc_serv/sage/local/lib/python2.7/site-packages/sage/knots/knot.pyc in connected_sum(self, other)

294         return Knot(B(list(b1.Tietze())

295                       + [(abs(i) + b2s) * Integer(i).sign() for i in b2.Tietze()]

--> 296                       + [b1s]))

297

/home/sc_serv/sage/local/lib/python2.7/site-packages/sage/knots/knot.pyc in __init__(self, data, check)

104         if check:

105             if self.number_of_components() != 1:

--> 106                 raise ValueError("the input has more than 1 connected component")

107

108     def __repr__(self):

ValueError: the input has more than 1 connected component


Am I doing something wrong here? Thanks in advance!