2017-11-13 22:25 GMT+01:00 <commits at source.squeak.org>:

> Nicolas Cellier uploaded a new version of Kernel to project The Inbox:
> http://source.squeak.org/inbox/Kernel-nice.1120.mcz
>
> ==================== Summary ====================
>
> Name: Kernel-nice.1120
> Author: nice
> Time: 13 November 2017, 10:24:19.857289 pm
> UUID: 24277641-be23-40ea-85ef-1db0d48f63d3
> Ancestors: Kernel-mt.1119
>
> 1) Use // in Fraction>>gcd:, rather than / will was invoking the same gcd:
> computation 4 times!
>
argh, "which was invoking", I did not finish to rephrase :(

2) Enhance the Fraction comment
>
This is in inbox because a class comment is something difficult to make
right and will benefit peer advices.
Feel free to improve!


> The Fraction comment SHALL tell about the expected class invariants.
> At least, it should help answering questions like:
>
> https://stackoverflow.com/questions/46942103/squeak-
> smalltalk-why-sometimes-the-reduced-method-doesnt-work
>
> https://stackoverflow.com/questions/46905203/squeak-
> smalltalk-why-reduction-of-a-fraction-does-not-happen-after-numerator-an
>
> While at it, also tell why 3 isFraction answers true, and 3.0 asFraction
> -> an Integer, not a Fraction.
> VW (st80?) has chosen better #isRational and #asRational messages for
> making things a bit more clear, but without a Rational superclass, it's not
> that obvious...
>
> =============== Diff against Kernel-mt.1119 ===============
>
> Item was changed:
>   Number subclass: #Fraction
>         instanceVariableNames: 'numerator denominator'
>         classVariableNames: ''
>         poolDictionaries: ''
>         category: 'Kernel-Numbers'!
>
> + !Fraction commentStamp: 'nice 11/13/2017 22:09' prior: 0!
> + Fraction provides methods for dealing with fractions like 1/3 as a ratio
> of two integers (as apposed to a decimal representation 0.33333...).
> - !Fraction commentStamp: '<historical>' prior: 0!
> - Fraction provides methods for dealing with fractions like 1/3 as
> fractions (not as 0.33333...).  All public arithmetic operations answer
> reduced fractions (see examples).
>
> + instance variables:
> +       numerator       <Integer> the number appearing before the fraction
> bar (above)
> +       denominator     <Integer> the number appearing after the fraction
> bar (below)
> +
> + A Fraction is generally created by sending the message / to an Integer,
> like in
> - instance variables: 'numerator denominator '
>
> +     1 / 3
> - Examples: (note the parentheses required to get the right answers in
> Smalltalk and Squeak):
>
> + Alternatively, it is possible to create a new instance of Fraction by
> sending #numerator:denominator: to the class.
> + In this later case, it is then user responsibility to ensure that it
> conforms to the following invariants:
> +
> + - the denominator shall allways be positive.
> +   A negative Fraction shall have a negative numerator, never a negative
> denominator.
> +   Example: 1 / -3 will return -1/3
> + - the denominator shall allways be greater than 1.
> +   A Fraction with denominator 1 shall be reduced to its numerator (an
> Integer).
> +   Example 3 / 1 will answer 3 (the Integer) not 3/1
> + - the numerator and denominator shall never have common multiples.
> +   Common multiples shall allways be simplified until (numerator gcd:
> denominator) = 1.
> +   Example 8 / 6 will answer 4 / 3, because both 8=2*4 and 6=2*3 are both
> divisible by 2.
> +
> + A Fraction non conforming to above invariants could be the cause of
> undefined behavior and unexpected results.
> + If unsure, it is advised to send the message #reduced to the freshly
> created instance so as to obtain a conforming Fraction, or an Integer.
> +
> + Note that Fraction and Integer represent together the set of Rational
> numbers:
> + - Integer is a subset of rational (those which are whole numbers)
> + - Fraction is used for representing the complementary subset of rational
> (those which are not whole numbers)
> +
> + There could have been a Rational superclass to both Integer and
> Fraction, and a message #isRational for testing if a Number is a Rational,
> as well as a message #asRational for converting a Number to a Rational.
> + But this level of indirection is not strictly necessary: instead, the
> notion of Rational and Fraction are collapsed in Squeak, and Integer are
> considered as a sort of special Fraction with unitary denominator.
> + Thus #isFraction is the testing message, to which every Integer will
> answer true, since considered as a sort of Fraction.
> + And #asFraction is the conversion message, that may answer an instance
> of Fraction of Integer, depending if the corresponding rational number is
> whole or not.
> +
> + All public arithmetic operations will answer reduced fractions.
> + Examples:
> +
>   (2/3) + (2/3)
> + (2/3) + (1/2)         "case showing reduction to common denominator"
> + (2/3) + (4/3)         "case where result is reduced to an Integer"
> + (2/3) raisedToInteger: 5               "fractions also can be
> exponentiated"
> - (2/3) + (1/2)          "answers shows the reduced fraction"
> - (2/3) raisedToInteger: 5               "fractions also can have
> exponents"
>   !
>
> Item was changed:
>   ----- Method: Fraction>>gcd: (in category 'arithmetic') -----
>   gcd: aFraction
>         | d |
>         d := denominator gcd: aFraction denominator.
> +       ^(numerator *(aFraction denominator//d) gcd: aFraction
> numerator*(denominator//d)) / (denominator//d*aFraction denominator)!
> -       ^(numerator *(aFraction denominator/d) gcd: aFraction
> numerator*(denominator/d)) / (denominator/d*aFraction denominator)!
>
>
>
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