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2017-11-16 20:30:41 +0200 | answered a question | how to create a matrix valued function? Like this? |

2017-10-24 01:22:34 +0200 | commented answer | Laurent series error q^2+O(q) is not O(q) Sorry, I don't really understand your way of preventing. I showed a simple example of how things can go wrong, which makes computations in Laurent series rings impossible because you can't even perform addition in there. For example, gives an error. I think you are right about the function |

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2017-10-19 16:08:25 +0200 | commented answer | Laurent series error q^2+O(q) is not O(q) The expectation is O(q). The same code works for power series and gives the desired result O(q) |

2017-10-18 22:13:58 +0200 | asked a question | Laurent series error q^2+O(q) is not O(q) I get an error for the following code: Any explanation? (works for PowerSeriesRing) Here is the error: Error in lines 2-2 Traceback (most recent call last): File "/cocalc/lib/python2.7/site-packages/smc_sagews/sage_server.py", line 996, in execute exec compile(block+'\n', '', 'single') in namespace, locals File "", line 1, in <module> File "sage/structure/element.pyx", line 1192, in sage.structure.element.Element.__add__ (/ext/sage/sage-8.0/src/build/cythonized/sage/structure/element.c:10640) return (<element>left)._add_(right) File "sage/rings/laurent_series_ring_element.pyx", line 622, in sage.rings.laurent_series_ring_element.LaurentSeries._add_ (/ext/sage/sage-8.0/src/build/cythonized/sage/rings/laurent_series_ring_element.c:8637) return right.add_bigoh(self.prec()) File "sage/rings/laurent_series_ring_element.pyx", line 691, in sage.rings.laurent_series_ring_element.LaurentSeries.add_bigoh (/ext/sage/sage-8.0/src/build/cythonized/sage/rings/laurent_series_ring_element.c:9742) u = self.__u.add_bigoh(prec - self.__n) File "sage/rings/power_series_ring_element.pyx", line 797, in sage.rings.power_series_ring_element.PowerSeries.add_bigoh (/ext/sage/sage-8.0/src/build/cythonized/sage/rings/power_series_ring_element.c:9029) return self._parent(v, prec) File "sage/structure/parent.pyx", line 936, in sage.structure.parent.Parent.__call__ (/ext/sage/sage-8.0/src/build/cythonized/sage/structure/parent.c:9826) return mor._call_with_args(x, args, kwds) File "sage/structure/coerce_maps.pyx", line 173, in sage.structure.coerce_maps.DefaultConvertMap_unique._call_with_args (/ext/sage/sage-8.0/src/build/cythonized/sage/structure/coerce_maps.c:5322) raise File "sage/structure/coerce_maps.pyx", line 166, in sage.structure.coerce_maps.DefaultConvertMap_unique._call_with_args (/ext/sage/sage-8.0/src/build/cythonized/sage/structure/coerce_maps.c:5161) return C._element_constructor(x, *args) File "/ext/sage/sage-8.0/local/lib/python2.7/site-packages/sage/rings/power_series_ring.py", line 783, in _element_constructor_ raise ValueError("prec (= %s) must be non-negative" % prec) ValueError: prec (= -1) must be non-negative |

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2017-10-16 16:26:59 +0200 | answered a question | Is there a way to get the homogeneous part of certain degree of a (multivariate) polynomial? If you don't want to write your own functions, you can also try adding O(d+1) in the corresponding power series ring to kill all higher order terms, then extract the polynomial back using .polynomial(), and then using your homogenize idea |

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2017-10-12 18:37:48 +0200 | commented answer | laurent series ring induced homomorphism Yes, I want something like this, but for Laurent series ring instead of Laurent polynomial ring. Somehow inducing homomorphisms in this manner works for Laurent polynomials and power series, but it doesn't seem to work for Laurent series. I know it is not hard to write the corresponding code, but I was just wondering if it is already implemented in sage |

2017-10-12 18:15:04 +0200 | commented answer | Simplifying rational expressions Let R be as in answer above (rational functions of x,y and z). Now let's consider R((q)) -formal Laurent series with coefficients in R. My problem is that sage keeps coefficients of those series not simplified (probably it thinks that all rational numbers are units and hence all the same) and also expanded. Now if I multiply two such series the coefficients become even worse (in sage's representation, but I know they can be simplified). So my question is: is there a way to make sage keep automatically simplifying coefficients every time I perform operations on Laurent series? Also I would really prefer if the coefficients were saved in a factored form if possible. Even if I call factor() for coefficients, when I print a series, the coefficients are in the expanded form. |

2017-10-11 18:05:11 +0200 | asked a question | laurent series ring induced homomorphism Can you not lift homomorphism of the base ring to the homomorphism of Laurent series ring in sage? (not manually) |

2017-10-11 17:24:46 +0200 | commented answer | Simplifying rational expressions That actually works, thanks! And now if I have a power series with coefficients in ring R as in your answer above, is there any way to make sage automatically simplify the coefficients without calling factor() for them? I am computing rather complicated expressions with a lot of steps, so I don't even know at what point I would need to call for it if I had to do it manually |

2017-10-11 09:23:17 +0200 | asked a question | Simplifying rational expressions I am working with a power series with coefficients being rational functions of several variables (everything over QQ). Is there any way to make sage automatically simplify the coefficients? Here is an example of what is going on And results: |

2017-10-11 09:23:16 +0200 | asked a question | Simplifying rational expressions I am working with a power series with coefficients being rational functions of several variables (everything over QQ). Is there any way to make sage automatically simplify the coefficients? Here is an example of what is going on And results: |

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