log to the base 2

[Michael Beeson]

sage: n(log(2,408/370))

7.08999206263157

sage: log(2,2)

1

sage: 2^7

128

sage: n(log(2,408.0/370))

7.08999206263157

sage: version()

'SageMath version 8.7, Release Date: 2019-03-23'

sage: n(log(2,1.001))

693.493696416899

sage:log(2,1)  gives an error instead of 0.

[Michael Beeson]

And also

sage: log(2,x)

log(2)/log(x)

which goes a long ways to explain the previous results.  So log(2,x) is not actually log to the base 2 of x.

[Reimundo Heluani]

sage: log?
Signature: log(*args, **kwds)
Docstring:
Return the logarithm of the first argument to the base of the
second argument which if missing defaults to "e".

It calls the "log" method of the first argument when computing the
logarithm, thus allowing the use of logarithm on any object
containing a "log" method. In other words, "log" works on more than
just real numbers.

So it should be

sage:
sage: log(1,2)
0

Which works fine.


Also on my Sage 9.2.beta2

sage: log(2,1)
Infinity

Cheers,

R.

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