What a comparison of a time or a date and time says of the values, as sets of their images (D-109).
The run compares two of them (Feel.Runtime.Temporal.compare/3) by their clocks when either has no zone, and by
their instants when both have one, at the second. A set has the three lines of Feel.Type.Moment (the clock of
the values with no zone, and the instant and the clock of those with a zone), and ? < y is, for the pairs of
classes that ? and y can be of:
? is | y is | ? < y is true for |
|---|---|---|
| no zone | no zone | a clock before that of y |
| no zone | a zone | a clock before the clock of y |
| a zone | no zone | a zoned clock before the clock of y (its instant follows, within the largest offset) |
| a zone | a zone | an instant before that of y (its zoned clock follows, within the largest offset) |
So the sets are exact for the class that y is, whichever ? is. The set of the values for which a comparison can be
true and the set for which it can be false are not each other's complement: a value 10 hours either side of y can be
either, when y may or may not have a zone. Feel.Analysis.TestSets reads both, as it does for a number, for the
narrowing of a name (Feel.Analysis.Narrowing) and for the allowed values of a variable.
Two sets are compared in the same way by decide/3, which says whether a comparison is true for every pair, false
for every pair, or for some.
iex> alias Feel.Type.{Moment, NumberSet}
iex> {:ok, date_time} = Feel.Value.DateTime.parse("2021-01-01T00:00:00")
iex> {:ok, images} = Moment.images(date_time)
iex> other = Enum.reduce(Enum.map(images, &NumberSet.point/1), &NumberSet.union/2)
iex> {before, _} = Feel.Analysis.MomentTests.compared(:date_and_time, :lt, other, false, true)
iex> Moment.format_member(:date_and_time, before)
"in [-999999999-01-01T00:00:00..2021-01-01T00:00:00) any zone"Summary
Functions
Returns {where? operator othercan be true, where it can be false} for a kind of moments, given the images that
other can be (numbers), whether it can be null, and whether it is one member of its type (a single value, if
the set says one).
Whether left operator right is true for every pair of images of the two sets (:always), false for every pair
(:never), or for some (:unknown). The images are compared as the run compares the values: the clocks of two with no
zone, the clock of one with no zone and the clock of one with a zone, and the instants of two with one.
Functions
@spec compared( Feel.Type.Moment.kind(), atom(), Feel.Type.NumberSet.t(), boolean(), boolean() ) :: {Feel.Type.NumberSet.t(), Feel.Type.NumberSet.t()}
Returns {where? operator othercan be true, where it can be false} for a kind of moments, given the images that
other can be (numbers), whether it can be null, and whether it is one member of its type (a single value, if
the set says one).
Both are supersets of the images for which the comparison is true and false, in the form of the kind
(Feel.Type.Moment.normalize/2).
@spec decide(atom(), Feel.Type.NumberSet.t(), Feel.Type.NumberSet.t()) :: :always | :never | :unknown
Whether left operator right is true for every pair of images of the two sets (:always), false for every pair
(:never), or for some (:unknown). The images are compared as the run compares the values: the clocks of two with no
zone, the clock of one with no zone and the clock of one with a zone, and the instants of two with one.
iex> alias Feel.Type.NumberSet
iex> a = NumberSet.interval(Decimal.new(0), Decimal.new(10))
iex> b = NumberSet.interval(Decimal.new(100), Decimal.new(110))
iex> Feel.Analysis.MomentTests.decide(:lt, a, b)
:always
iex> Feel.Analysis.MomentTests.decide(:gt, a, b)
:never