Reusing output of QEPCAD

qepcad

asked 2021-07-01 08:58:27 +0100

philipp7
391 ●6 ●12 ●28

Suppose we get a quantifier-free formula as an output from QEPCAD and we want to use that formula as an input for another call to QEPCAD. How can this be done? The naive approach does not work as the following example shows (a very trivial example as the first qepcad call does not actually do much):

sage: var("a,b")
sage: formula = qepcad(a+b==0)
sage: print(formula)
b + a = 0
sage: qepcad_formula.exists(b,formula)

yields the error

ValueError: Attempting to quantify variable which does not occur in formula

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answered 2021-07-01 09:10:10 +0100

philipp7
391 ●6 ●12 ●28

Sorry, already got it. For anyone else needing this at some point, there is the function qformula which can be used. The example above then yields

sage: from sage.interfaces.qepcad import qformula
sage: var("a,b")
sage: formula = qepcad(a+b==0)
sage: qepcad_formula.exists(b,qformula(formula,frozenset(['a','b'])))
(E b)[b + a = 0]

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Well done. You can accept your own answer to mark the question as solved.

slelievre ( 2021-07-01 15:27:56 +0100 )edit

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Asked: 2021-07-01 08:58:27 +0100

Seen: 187 times

Last updated: Jul 01 '21

Reusing output of QEPCAD edit