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2020-01-11 22:18:37 +0200 | commented answer | Eigenvalues and eigenspaces of orthogonal (or rotation) matrices Thanks, this is excellent! (I need the actual fractions (1/5,2/5,3/5,4/5 in the example) which I can now deduce inductively from your code using the multiplicities, and then I suppose I can obtain the eigenspaces by first comparing those eigenvalues with E(5)^i in UniversalCyclotomicField, and then taking the real and complex parts of the matching eigenvectors gives the rotation planes. In other words, this is very doable now but if you know some smart tricks for this again then please do let me know!) |

2020-01-10 23:05:24 +0200 | asked a question | Eigenvalues and eigenspaces of orthogonal (or rotation) matrices Given an orthogonal transformation of finite order, e.g. Its eigenvalues are going to be of the form corresponding to a splitting of the matrix into rotation (and reflection) matrices. I'd like to extract these fractions My impression is that Sage isn't suitable for doing this directly, but that I should use e.g. the Maxima or Mathematica interface? Any suggestions for the most suitable method? |

2020-01-05 02:20:41 +0200 | commented answer | Cython: undeclared name not builtin ... and that's exactly what you meant. Woops! |

2020-01-04 22:15:51 +0200 | commented answer | Cython: undeclared name not builtin Sorry I'm new to this, but |

2020-01-03 21:11:55 +0200 | commented answer | Cython: undeclared name not builtin Thanks, this was helpful - the right answer is |

2020-01-03 17:32:28 +0200 | asked a question | Cython: undeclared name not builtin Loading a .spyx file with yields Is there a library that I need to include? |

2020-01-01 02:46:37 +0200 | commented answer | Local/global variable behaviour of lists This is clear, thanks! This leaves me with two minor questions: . Do you know why variables are immutable and lists are mutable by design? At first glance it might seem more useful (?) if the changes to a list remain "local" to the function, just like the changes to the variable x in bla . What are elegant ways to write functions like bla2 without modifying L? Tuples don't seem to work for this purpose, so instead of bla3 just copy L inside the function via K = L[:]? |

2019-12-31 18:41:55 +0200 | asked a question | Local/global variable behaviour of lists (This might be, in some way, related to this bug). I recently discovered the following behaviour, which I found quite surprising - if this is intentional, can someone please explain to me why this is supposed to happen? Defining and then running bla(x) does not change the value of x, but running bla2(L) or bla3(L) DOES change the value of L to [2]. |

2019-11-26 20:28:42 +0200 | commented question | Bug: Gap3 interface confuses variables Yes, the CHEVIE package - currently I'm doing some computations with braids. |

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2019-11-17 14:43:19 +0200 | commented answer | Entries in canonical_matrix for Coxeter groups Woops, thanks! |

2019-11-17 14:41:52 +0200 | asked a question | Bug: Gap3 interface confuses variables Running followed up by yields instead of 4,5,6,4. Is this a bug or am I doing this wrong? Update: I've tried it on a different computer (which uses a slightly older version of Sage) and did not have any issues there. I'm running the latest version of Sage here; any idea what might be causing this? Update2: I'm experiencing the exact same problem on the other computer, when running slightly more complicated code: the gap3 interface seems to override its variables with other outputs. |

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2019-11-06 20:16:53 +0200 | asked a question | Entries in canonical_matrix for Coxeter groups Can anyone please tell me what
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