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Unable to convert string to rational when plus sign is added

asked 2020-01-13 16:24:53 -0500

Jose Brox gravatar image

updated 2020-01-13 16:26:25 -0500

This looks like a bug. The code

QQ('+1')

gives the exception

TypeError: unable to convert '+1' to a rational

This happens with any positive rational, not just 1.

Also, this does not happen with neither

ZZ('+1')

nor

PolynomialRing(QQ,names='x')('+1')

Is this actually a bug? If it is, can someone investigate it and write a trac ticket? I'm quite new to Sagemath and Python and quite unskilled yet to do it properly. Thank you!

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answered 2020-01-13 22:46:40 -0500

As far as I can tell, Sage uses gmp(https://gmplib.org) to construct its rational numbers, and the gmp function mpq_set_strdoesn't handle the leading plus sign. In any case, I would call it a lack of a feature rather than a bug. I've opened https://trac.sagemath.org/ticket/29006.

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Asked: 2020-01-13 16:24:53 -0500

Seen: 38 times

Last updated: Jan 13