Pharo Issue Tracker - Manuscript (Case [Issue]21569) Kernel - DateAndTime should not use respondsTo logic in minus operation

Manuscript Notification

	OleksandrZaytsev edited Case 21569: DateAndTime should not use respondsTo logic in minus operation: Cleanup in Kernel: 1. Pharo Image • You are subscribed to this case

Perhaps the conversions to DateAndTime and Duration should not happen implicitly. Right now we have this complex logic because we want to support things like this:

<code>
t := '2004-01-07T11:55:00+00:00' asDateAndTime.
t - 5.
t - '2004-01-07'
</code>

But maybe we shouldn't. It doesn't make much sense to subtract a string or a number (number of what? days? seconds?) from a DateAndTime object. And whoever is using this can easily do an explicit conversion, which, by the way, would also make his code more readable.

<code>
t - 5 asDuration.
t - '2004-01-07' asTimeAndDate
</code>

I've implemented a new version using double dispatch:

<code>
DateAndTime >> - operand
"operand is either DateAndTime or Duration"

^ operand subtractFromDateAndTime: self.

DateAndTime >> subtractFromDateAndTime: aDateAndTime
^ Duration
seconds: (SecondsInDay * (aDateAndTime julianDayNumberUTC - julianDayNumber))
+ (aDateAndTime secondsSinceMidnightUTC - seconds)
nanoSeconds: aDateAndTime nanoSecond - nanos.

Duration >> subtractFromDateAndTime: aDateAndTime

^ aDateAndTime + self negated.
</code>

And I suggest that we mark the previous implementation as deprecated because some code might depend on it.

	Priority: 5 – Fix If Time		Status: Work Needed
	Assigned to: Everyone		Milestone: Pharo7.0

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