Nicolas Cellier uploaded a new version of Kernel to project The Trunk: http://source.squeak.org/trunk/Kernel-nice.1213.mcz
==================== Summary ====================
Name: Kernel-nice.1213 Author: nice Time: 8 February 2019, 11:24:45.054968 pm UUID: d7a472c9-49dd-4b1d-b73a-13b9c7c8d4c5 Ancestors: Kernel-tonyg.1212
Provide a logarithm in base 2: log2. This (x log2) has an additional property that (x log: 2) has not: it is exact for exact powers of 2.
While implementing LogarithmicInterval, I recently wanted to use log: 2, and this was getting as bad as in Python. See https://stackoverflow.com/questions/931995/inaccurate-logarithm-in-python/54...
I don't know if this feature is really worth it, but whether it ends up integrated or not, at least it demonstrates how easy it is to patch Squeak.
=============== Diff against Kernel-tonyg.1212 ===============
Item was added: + ----- Method: Float>>log2 (in category 'mathematical functions') ----- + log2 + "Answer the base 2 logarithm of the receiver. + Arrange to answer exact result in case of exact power of 2." + + ^ self significand ln / Ln2 + self exponent!
Item was added: + ----- Method: Fraction>>log2 (in category 'mathematical functions') ----- + log2 + "This function is defined because super log might overflow." + | res | + self <= 0 ifTrue: [DomainError signal: 'log2 is only defined for x > 0']. + "Test self < 1 before converting to float in order to avoid precision loss due to gradual underflow." + numerator < denominator ifTrue: [^self reciprocal log2 negated]. + res := super log2. + res isFinite ifTrue: [^res]. + ^numerator log2 - denominator log2!
Item was added: + ----- Method: Integer>>log2 (in category 'mathematical functions') ----- + log2 + self > 0 ifTrue: [^super log2]. + ^DomainError signal: 'log2 is only defined for x > 0'!
Item was added: + ----- Method: LargeNegativeInteger>>log2 (in category 'mathematical functions') ----- + log2 + ^DomainError signal: 'log2 is only defined for x > 0'!
Item was added: + ----- Method: LargePositiveInteger>>log2 (in category 'mathematical functions') ----- + log2 + "This function is defined because super log2 might overflow." + | res h | + res := super log2. + res isFinite ifTrue: [^res]. + h := self highBit. + ^h + (self / (1 << h)) asFloat log2!
Item was added: + ----- Method: Number>>log2 (in category 'mathematical functions') ----- + log2 + "Answer the base-2 log of the receiver." + + ^self asFloat log2!
Item was changed: ----- Method: Number>>log: (in category 'mathematical functions') ----- log: aNumber "Answer the log base aNumber of the receiver."
+ aNumber = 2 ifTrue: [^self log2]. ^self ln / aNumber ln!
Item was added: + ----- Method: ScaledDecimal>>log2 (in category 'mathematical functions') ----- + log2 + "Unlike super, avoid Float overflow/underflow" + + ^self asFraction log2!