I’ve been trying to get the maximum of a list of counts. I started by using
“myCollection.map { $0.myCountProperty }.reduce(0, max)”. Then I thought I
should really use the value closest to negative infinity as the base. The
problem is how to get that value. The current hard-coded “0” works because the
count type ultimately aliases “Int”, but shouldn’t have to count on that. I put
in “MyCountType.min”, where “MyCountType” is hard coded from the docs of
“myCountProperty”, but I shouldn’t have to do that either.
There is a “type(of:)” global function, which I did use. But not only did I
have to make up an expression to go in there, its return value, some sort of
meta-type stuff I don’t understand, can’t be used on the right side of a
“typealias” construct. I ultimately used “let lowestCount = type(of:
anElement.myCountProperty).min” to get what I needed.
Some queries/requests:
1. Is the expression within “type(of:)” evaluated?
2. I think we need the equivalent of "std::declval” from C++. Especially if the
answer to (1) is yes.
3. Why isn’t the return type(?) of “type(of:)” compile-time enough to be used
as a type-alias?
4. Should we add something like the C++ type-traits collection of generic
structures to give use type information as type-aliases or type-level instances?
—
Daryle Walker
Mac, Internet, and Video Game Junkie
darylew AT mac DOT com
_______________________________________________
swift-evolution mailing list
[email protected]
https://lists.swift.org/mailman/listinfo/swift-evolution
