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unexpected(?) conversion to float while raising an integer to power -1 [closed]

asked 2021-06-21 19:57:54 +0200

Max Alekseyev gravatar image

This is what I observe in Sage 9.3:

sage: type(29**(-1))                                                                                                                                                                                       
<class 'sage.rings.rational.Rational'>
sage: type(ZZ(29)**(-1))                                                                                                                                                                                   
<class 'sage.rings.rational.Rational'>
sage: type(int(29)**(-1))                                                                                                                                                                                  
<class 'float'>

Why the last result is 'float'? Is it a bug or an expected behavior?

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Closed for the following reason the question is answered, right answer was accepted by Max Alekseyev
close date 2021-11-10 17:25:56.423544

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answered 2021-06-21 20:14:54 +0200

tmonteil gravatar image

This is the expected behaviour. When you type 29, the Sage preparser ensures that this number is considered as a Sage integer, whose inverse is a rational number. When you write int(29), the resulting number is a Python integer, whose inverse is a float (i.e. the basic representation of real numbers in Python3).

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Asked: 2021-06-21 19:57:54 +0200

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Last updated: Jun 21 '21