The Trunk: Kernel-nice.1054.mcz

Nicolas Cellier uploaded a new version of Kernel to project The Trunk:
http://source.squeak.org/trunk/Kernel-nice.1054.mcz

==================== Summary ====================

Name: Kernel-nice.1054
Author: nice
Time: 27 January 2017, 9:44:46.83377 pm
UUID: ef21d74d-ba81-47c6-9bb7-92fb4140f494
Ancestors: Kernel-eem.1053

Change -0.0 sign to answer 0 instead of -1.
Introduce a new message signBit for recognition of Float negativeZero.

Rationale:
1) The value of Float negativeZero cannot be distinguished from zero.
   Thus (Float negativeZero = 0.0)
   We can then expect sign to be symmetric for (positive) zero and negativeZero
2) ANSI Smalltalk requires above behavior.
   This will reduce un-necessary difference with Gemstone for example.

About NaN:
Note that with old implementation, the sign of "positive" nan was 0, while it was -1 for "negative" nan.
New implementation will allways answer 0 for nans.

We may as well answer Float nan, but currently sign will allways answer an Integer (-1,0 or 1). Until it is well specified by a standard, let's not bother.
Otherwise, we could answer a Float if receiver is a Float like:

sign
        self > 0.0 ifTrue: [ ^1.0].
        self < 0.0 ifTrue: [ ^-1.0].
        ^self

=============== Diff against Kernel-eem.1053 ===============

Item was changed:
  ----- Method: Float>>arcTan: (in category 'mathematical functions') -----
  arcTan: denominator
+ "Answer the angle in radians, taking care of 4 quadrants.
+ Implementation note: use signBit and sign: in order to catch cases of negativeZero"
- "Answer the angle in radians.
- Optional. See Object documentation whatIsAPrimitive.
- Implementation note: use sign in order to catch cases of negativeZero"
 
+ self = 0.0
+ ifTrue:
+ [denominator signBit = 0 ifTrue: [ ^0.0 ].
+ ^Pi sign: self ].
+ denominator = 0.0 ifTrue: [ ^Halfpi sign: self ].
+ denominator > 0.0 ifTrue: [ ^(self / denominator) arcTan ].
+ ^(self / denominator) arcTan + (Pi sign: self)!
- self = 0.0 ifTrue: [
- denominator sign >= 0 ifTrue: [ ^0.0 ].
- self sign >= 0 ifTrue: [ ^Pi ].
- ^0.0 - Pi ].
- denominator = 0.0 ifTrue: [
- self > 0.0 ifTrue: [ ^Halfpi ].
- ^0.0 - Halfpi ].
- denominator > 0.0 ifTrue: [  ^(self / denominator) arcTan ].
- self > 0.0 ifTrue: [ ^(self / denominator) arcTan + Pi ].
- ^(self / denominator) arcTan - Pi!

Item was changed:
  ----- Method: Float>>byteEncode:base: (in category 'printing') -----
  byteEncode: aStream base: base
  "Handle sign, zero, and NaNs; all other values passed to absPrintOn:base:"
 
  self isNaN ifTrue: [aStream print: 'NaN'. ^ self]. "check for NaN before sign"
  self > 0.0
  ifTrue: [self absByteEncode: aStream base: base]
  ifFalse:
+ [self signBit = 1
- [self sign = -1
  ifTrue: [aStream print: '-'].
  self = 0.0
  ifTrue: [aStream print: '0.0'. ^ self]
  ifFalse: [aStream writeNumber:self negated base: base]]!

Item was removed:
- ----- Method: Float>>copySignTo: (in category 'mathematical functions') -----
- copySignTo: aNumber
- "Return a number with same magnitude as aNumber and same sign as self.
- Implementation note: take care of Float negativeZero, which is considered as having a negative sign."
-
- (self > 0.0 or: [(self at: 1) = 0]) ifTrue: [^ aNumber abs].
- ^aNumber withNegativeSign!

Item was changed:
  ----- Method: Float>>printOn:base: (in category 'printing') -----
  printOn: aStream base: base
  "Print the receiver with the minimal number of digits that describes it unambiguously.
  This way, every two different Float will have a different printed representation.
  More over, every Float can be reconstructed from its printed representation with #readFrom:."
 
  self isNaN ifTrue: [aStream nextPutAll: 'NaN'. ^ self]. "check for NaN before sign"
  self > 0.0
  ifTrue: [self absPrintExactlyOn: aStream base: base]
  ifFalse:
+ [self signBit = 1
- [self sign = -1
  ifTrue: [aStream nextPutAll: '-'].
  self = 0.0
  ifTrue: [aStream nextPutAll: '0.0']
  ifFalse: [self negated absPrintExactlyOn: aStream base: base]]!

Item was changed:
  ----- Method: Float>>printOn:maxDecimalPlaces: (in category 'printing') -----
  printOn: aStream maxDecimalPlaces: placesDesired
  "Refine super implementation in order to avoid any rounding error caused by rounded or roundTo:"
 
  self isFinite ifFalse: [^self printOn: aStream].
  self > 0.0
  ifTrue: [self absPrintExactlyOn: aStream base: 10 decimalPlaces: placesDesired showTrailingFractionalZeros: false]
  ifFalse:
+ [self signBit = 1
- [self sign = -1
  ifTrue: [aStream nextPutAll: '-'].
  self = 0.0
  ifTrue: [aStream nextPutAll: '0.0']
  ifFalse: [self absPrintExactlyOn: aStream base: 10 decimalPlaces: placesDesired showTrailingFractionalZeros: false]]!

Item was changed:
  ----- Method: Float>>printOn:showingDecimalPlaces: (in category 'printing') -----
  printOn: aStream showingDecimalPlaces: placesDesired
  "Refine super implementation in order to avoid any rounding error caused by rounded or roundTo:"
 
  self isFinite ifFalse: [^self printOn: aStream].
  self > 0.0
  ifTrue: [self absPrintExactlyOn: aStream base: 10 decimalPlaces: placesDesired showTrailingFractionalZeros: true]
  ifFalse:
+ [self signBit = 1
- [self sign = -1
  ifTrue: [aStream nextPutAll: '-'].
  self = 0.0
  ifTrue:
  [aStream nextPut: $0.
  placesDesired > 0 ifTrue: [aStream nextPut: $.; next: placesDesired put: $0]]
  ifFalse: [self absPrintExactlyOn: aStream base: 10 decimalPlaces: placesDesired showTrailingFractionalZeros: true]]!

Item was removed:
- ----- Method: Float>>sign (in category 'mathematical functions') -----
- sign
- "Answer 1 if the receiver is greater than 0, -1 if less than 0, else 0.
- Handle IEEE-754 negative-zero by reporting a sign of -1"
-
- self > 0.0 ifTrue: [ ^1 ].
- self < 0.0 ifTrue: [ ^-1 ].
- ^0 - ((self at: 1) bitShift: -31) "-1 for negative zero, 0 otherwise"!

Item was removed:
- ----- Method: Float>>sign: (in category 'mathematical functions') -----
- sign: aNumber
- "Return a Number with the same sign as aNumber and same magnitude as self.
- Implementation is different from super to handle the special case of Float negativeZero."
-
- (self = 0.0 and: [aNumber sign negative]) ifTrue: [^Float negativeZero].
- ^aNumber copySignTo: self!

Item was added:
+ ----- Method: Float>>signBit (in category 'mathematical functions') -----
+ signBit
+ "Answer 1 if the receiver has sign bit set (including case of IEEE-754 negative-zero).
+ Answer 0 otherwise"
+
+ ^((self at: 1) bitShift: -31)!

Item was changed:
  ----- Method: Float>>storeOn:base: (in category 'printing') -----
  storeOn: aStream base: base
  "Print the Number exactly so it can be interpreted back unchanged"
  self isFinite
+ ifTrue: [self signBit = 1 ifTrue: [aStream nextPutAll: '-'].
- ifTrue: [self sign = -1 ifTrue: [aStream nextPutAll: '-'].
  base = 10 ifFalse: [aStream print: base; nextPut: $r].
  self = 0.0
  ifTrue: [aStream nextPutAll: '0.0']
  ifFalse: [self abs absPrintExactlyOn: aStream base: base]]
  ifFalse: [self isNaN
  ifTrue: [aStream nextPutAll: 'Float nan']
  ifFalse: [self > 0.0
  ifTrue: [aStream nextPutAll: 'Float infinity']
  ifFalse: [aStream nextPutAll: 'Float infinity negated']]]!

Item was removed:
- ----- Method: Float>>withNegativeSign (in category 'converting') -----
- withNegativeSign
- "Same as super, but handle the subtle case of Float negativeZero"
-
- self = 0.0 ifTrue: [^self class negativeZero].  
- ^super withNegativeSign!

Item was added:
+ ----- Method: LargeNegativeInteger>>signBit (in category 'testing') -----
+ signBit
+ "Optimization."
+
+ ^1
+ !

Item was added:
+ ----- Method: LargePositiveInteger>>signBit (in category 'testing') -----
+ signBit
+ "Optimization."
+
+ ^0!

Item was changed:
  ----- Method: Number>>copySignTo: (in category 'mathematical functions') -----
  copySignTo: aNumber
  "Return a number with same magnitude as aNumber and same sign as self."
 
+ ^ self signBit = 0
- ^ self positive
  ifTrue: [aNumber abs]
+ ifFalse: [aNumber abs negated].!
- ifFalse: [aNumber withNegativeSign].!

Item was added:
+ ----- Method: Number>>signBit (in category 'mathematical functions') -----
+ signBit
+ "Answer 1 if the receiver is negative, zero otherwise."
+
+ self < 0 ifTrue: [^1].
+ ^0!

Item was removed:
- ----- Method: Number>>withNegativeSign (in category 'converting') -----
- withNegativeSign
- "Answer a number with same magnitude than receiver and negative sign."
- ^self abs negated!