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20130712 02:10:02 0500  answered a question  PolyBoRi Version in Sage 5.9 There is probably a better way to find out if you have Sage 5.9 installed, but here is a quick answer. You'll see that the polybori package in the standard Sage distribution has version 0.8.3 here: 
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20130607 02:29:32 0500  edited question  spam please close Spam link is in the answer. 
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20130522 00:12:29 0500  answered a question  substitution in expression The substitute command is a generic interface to the rewrite engine in Pynac/GiNaC. You can replace an arbitrary subexpression, also containing wildcards (see the documentation of the Consider the case where a subexpression occurs in several places and you have a better formula or value for it derived from other sources. You can just replace the existing subexpression with the new formula using the 
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20130515 01:29:20 0500  answered a question  simplify and latex_name This is a bug. I opened a ticket on trac, see #14590. Thanks for the feedback. 
20130505 02:36:02 0500  answered a question  Conversion of Differential Forms to a manipulable symbolic expression It's a terrible hack, but perhaps this will help you as a workaround: That's what you have already. Now, we convert 
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20130307 07:19:21 0500  commented question  polynomial digits of pi This seems like a homework question. 
20130304 23:50:12 0500  answered a question  How to print out Maxima commands being used by Sage? Sage sets the domain of all variables to If you want to take a look at the code, Maxima initialization is done at the beginning of 
20130304 21:20:18 0500  answered a question  Solving simultaneous boolean algebraic equations Looking into the PolyBoRi interface, especially the 
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20130219 03:17:14 0500  answered a question  Evaluate expression with unknowns You need the 
20130210 02:30:12 0500  answered a question  variables vs arguments For symbolic expressions, For callable expressions, they differ: 
20130210 01:17:29 0500  answered a question  Using pyglet in sage? Sage installs its own version of Python and many other mathematics packages independent of the host operating system. You would need to install pyglet in this environment. You can do this with on the Sage ipython prompt. This was also answered here. 
20130125 17:41:37 0500  answered a question  Passing params to cythonized ode_system() I guess you mean the example at the end of the Solving ODE numerically by GSL section. You can add a constructor to your class which takes params as an argument and stores it in the instance created. The code to use this would be (mostly copied from the reference manual) The new class would look like: In terms of performance, there is a problem with this code. The elements of params are Sage types, either Python floats, RDF elements,
or even multiprecision floats (backed by MPFR). Whenever these are
multiplied by a To work around this, you can convert params to a vector of doubles in the constructor. Assuming params has 3 elements, then the first lines of the class would be 
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20130116 22:39:20 0500  commented question  sage sample This sounds a lot like homework. 
20130116 04:46:03 0500  answered a question  subs(_expr) not working properly? When asked to replace Try this instead: More information available in the relevant section of the GiNaC tutorial. 
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20130114 22:52:56 0500  answered a question  How can I use turtle module? This looks like a generic Python question. In this case, Google might be more helpful than this site. Here is the first hit. 
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20130113 21:58:50 0500  commented question  definition of gcd for(x,y) I guess the context here is given by http://en.wikipedia.org/wiki/GCD_test. This is offtopic. 
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20130112 11:41:21 0500  answered a question  Defining Clifford Algebras GiNaC, the C++ library used as the backend for symbolic expressions in Sage, supports Clifford algebras. See this article for more details. Using this implementation might be easier than starting from scratch in Python/Cython. I expect the performance of GiNaC to be quite competitive, thanks to Pynac we can also use arbitrary coefficient domains from Sage. After a brief look at the article mentioned above, I can say that it would be fairly straightforward to wrap those C++ functions and provide access to these data structures from Sage. I would be happy to do this and create a prototype implementation if somebody is willing to take over the polish. :) 
20130112 10:00:00 0500  answered a question  How to use cython functions from other cython cells in notbook? This works for me: The function name 
20130104 03:19:09 0500  commented answer  Express domain membership Then you can mark my answer as the accepted one. This will prevent this question from getting in the way if someone searches for the list of unanswered questions on this site. 
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20130102 01:55:52 0500  answered a question  Express domain membership
In this case, to indicate that the variable Unfortunately, Sage relies on two different backends for symbolic computations, Maxima and Pynac. Each of these uses a different method to indicate domains. We haven't reconciled these through the same interface yet. In order to indicate that a variable is real to Pynac, you can do: At this moment, Pynac does not have different domains for 
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20121218 22:06:16 0500  answered a question  Does a subtraction symbolic expression actually exist? We only use For example: You can read more about the internal representation of expressions in the relevant part of the GiNaC tutorial. The patch attached to ticket #13738 wraps some internal GiNaC functions to view the expression tree. 
20121203 00:29:57 0500  answered a question  Object Persistence db_save error Python does not know how to save the state of the generator object. You need to define methods to "pickle" and "unpickle" your object, i.e., save a persistent state and read it back. There is some documentation for this in the pickle section of the Python documentation. Especially this section on pickling normal class instances is relevant. Essentially, you need to define two methods 
20121202 21:15:56 0500  answered a question  System of polynomial inequalities You can use the cylindirical algebraic decomposition (CAD) method to solve a system of polynomials with inequalities. Sage has an optional package for QEPCAD. See the output of and try from the command line to install QEPCAD. Note that the version we have ( 
20121129 18:27:37 0500  edited question  creating a matrix from blocks I am new to SAGE. I need to create a matrix by using matrices of different sizes. For example: where A and B are 2x2's, C is a 2x1, D is a 1x2, and E is a 1x1. I do not need Abar to be a partitioned matrix. Thanks much. 
20121126 00:09:20 0500  answered a question  Forcing Prime Notation You can try the patch attached to issue #6344. It is more than 3 years old, so some work might be needed to make it apply to a recent Sage version, but it essentially does exactly what you need. See this comment for some examples. 
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20121122 21:11:55 0500  answered a question  Why simplify doesn't work?
