I'm proposing a new extension method on SequenceType called find(). It's similar to CollectionType.indexOf() except it returns the element:
extension SequenceType {
/// Returns the first element where `predicate` returns `true`, or `nil`
/// if such value is not found.
public func find(@noescape predicate: (Self.Generator.Element) throws ->
Bool) rethrows -> Self.Generator.Element? {
for elt in self {
if try predicate(elt) {
return elt
}
}
return nil
}
}
-Kevin Ballard
+1. We've added an extension for this and find it very useful.
On Tue, Dec 29, 2015 at 18:38 Kevin Ballard via swift-evolution < swift-evolution@swift.org> wrote:
I'm proposing a new extension method on SequenceType called find(). It's
similar to CollectionType.indexOf() except it returns the element:extension SequenceType {
/// Returns the first element where `predicate` returns `true`, or
`nil`/// if such value is not found.
public func find(@noescape predicate: (Self.Generator.Element) throws
-> Bool) rethrows -> Self.Generator.Element? {for elt in self {
if try predicate(elt) {
return elt
}
}
return nil
}
}
-Kevin Ballard
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swift-evolution@swift.org
https://lists.swift.org/mailman/listinfo/swift-evolution
Proposal PR submitted as Proposal: Add function SequenceType.find(_:) by lilyball · Pull Request #94 · apple/swift-evolution · GitHub
-Kevin Ballard
On Tue, Dec 29, 2015, at 06:38 PM, Kevin Ballard wrote:
I'm proposing a new extension method on SequenceType called find().
It's similar to CollectionType.indexOf() except it returns the
element:extensionSequenceType {
/// Returns the first element where `predicate` returns `true`,
or `nil`
/// if such value is not found.
public func find(@noescape predicate: (Self.Generator.Element) throws
-> Bool) rethrows -> Self.Generator.Element? {
for elt in self {
if try predicate(elt) {
return elt
}
}
return nil
}
}
-Kevin Ballard
+1. Like others, this was one of the first stdlib extensions I’ve put into my Swift projects. It’s very common to want to find the first matching element in an array (or, perhaps even more common, find what you know if the only matching element — `filter` without the extra step of unpacking the value from array.)
It’s also common in other languages, and `find` is a good name.
— Radek
On 30 Dec 2015, at 03:38, Kevin Ballard via swift-evolution <swift-evolution@swift.org> wrote:
I'm proposing a new extension method on SequenceType called find(). It's similar to CollectionType.indexOf() except it returns the element:
extension SequenceType {
/// Returns the first element where `predicate` returns `true`, or `nil`
/// if such value is not found.
public func find(@noescape predicate: (Self.Generator.Element) throws -> Bool) rethrows -> Self.Generator.Element? {
for elt in self {
if try predicate(elt) {
return elt
}
}
return nil
}
}-Kevin Ballard
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https://lists.swift.org/mailman/listinfo/swift-evolution
We should add the full collection of ruby methods http://matthewcarriere.com/06/23/using-select-reject-collect-inject-and-detect/
Sent from my iPhone
On 30 Dec 2015, at 02:40, Keith Smiley via swift-evolution <swift-evolution@swift.org> wrote:
+1. We've added an extension for this and find it very useful.
On Tue, Dec 29, 2015 at 18:38 Kevin Ballard via swift-evolution <swift-evolution@swift.org> wrote:
I'm proposing a new extension method on SequenceType called find(). It's similar to CollectionType.indexOf() except it returns the element:extension SequenceType {
/// Returns the first element where `predicate` returns `true`, or `nil`
/// if such value is not found.
public func find(@noescape predicate: (Self.Generator.Element) throws -> Bool) rethrows -> Self.Generator.Element? {
for elt in self {
if try predicate(elt) {
return elt
}
}
return nil
}
}-Kevin Ballard
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+1 we also have a very similar extension.
On Wed, Dec 30, 2015 at 1:40 PM, Keith Smiley via swift-evolution < swift-evolution@swift.org> wrote:
+1. We've added an extension for this and find it very useful.
On Tue, Dec 29, 2015 at 18:38 Kevin Ballard via swift-evolution < > swift-evolution@swift.org> wrote:I'm proposing a new extension method on SequenceType called find(). It's
similar to CollectionType.indexOf() except it returns the element:extension SequenceType {
/// Returns the first element where `predicate` returns `true`, or
`nil`/// if such value is not found.
public func find(@noescape predicate: (Self.Generator.Element) throws
-> Bool) rethrows -> Self.Generator.Element? {for elt in self {
if try predicate(elt) {
return elt
}
}
return nil
}
}
-Kevin Ballard
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Is it worth considering a version that returns a tuple of (index, element) ?
Nevin
On Tue, Dec 29, 2015 at 9:40 PM, Keith Smiley via swift-evolution < swift-evolution@swift.org> wrote:
+1. We've added an extension for this and find it very useful.
On Tue, Dec 29, 2015 at 18:38 Kevin Ballard via swift-evolution < > swift-evolution@swift.org> wrote:I'm proposing a new extension method on SequenceType called find(). It's
similar to CollectionType.indexOf() except it returns the element:extension SequenceType {
/// Returns the first element where `predicate` returns `true`, or
`nil`/// if such value is not found.
public func find(@noescape predicate: (Self.Generator.Element) throws
-> Bool) rethrows -> Self.Generator.Element? {for elt in self {
if try predicate(elt) {
return elt
}
}
return nil
}
}
-Kevin Ballard
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I just saw this PR and have a quick comment about the implementation: It could be shortened by a few lines using a where clause like this:
func find(@noescape predicate: Self.Generator.Element throws -> Bool) rethrows -> Self.Generator.Element? {
for element in self where try predicate(element) {
return element
}
return nil
}
Also, I’d like suggest adding a variant that works better with heterogenous sequences, but I’ll raise that when this proposal goes into review.
FYI: That variant would look like this:
func find<T>(_: T.Type, @noescape matching predicate: T throws -> Bool) rethrows -> T?
A question by me on the swift-users mailing list describes its intention, implementation, and usage:
[swift-users] Which is the more idiomatic approach for pinning down the type of a generic parameter? <https://lists.swift.org/pipermail/swift-users/Week-of-Mon-20160118/000893.html>
Cheers,
Marco
On 2016-01-10, at 01:58, Kevin Ballard via swift-evolution <swift-evolution@swift.org> wrote:
Proposal PR submitted as Proposal: Add function SequenceType.find(_:) by lilyball · Pull Request #94 · apple/swift-evolution · GitHub
-Kevin Ballard
On Tue, Dec 29, 2015, at 06:38 PM, Kevin Ballard wrote:
I'm proposing a new extension method on SequenceType called find(). It's similar to CollectionType.indexOf() except it returns the element:
extensionSequenceType {
/// Returns the first element where `predicate` returns `true`, or `nil`
/// if such value is not found.
public func find(@noescape predicate: (Self.Generator.Element) throws -> Bool) rethrows -> Self.Generator.Element? {
for elt in self {
if try predicate(elt) {
return elt
}
}
return nil
}
}-Kevin Ballard
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swift-evolution@swift.org
https://lists.swift.org/mailman/listinfo/swift-evolution
+1. Like others, this was one of the first stdlib extensions I’ve put
into my Swift projects. It’s very common to want to find the first
matching element in an array (or, perhaps even more common, find what
you know if the only matching element — `filter` without the extra
step of unpacking the value from array.)It’s also common in other languages, and `find` is a good name.
My only hesitation is that find has the strong connotation of not
modifying the underlying sequence, but any single-pass sequence will be
consumed. I don't know why that should bother me, though, considering
the many other such methods we have defined on SequenceType.
on Wed Feb 17 2016, Radosław Pietruszewski <swift-evolution@swift.org> wrote:
— Radek
On 30 Dec 2015, at 03:38, Kevin Ballard via swift-evolution <swift-evolution@swift.org> wrote:
I'm proposing a new extension method on SequenceType called find(). It's similar to CollectionType.indexOf() except it returns the element:
extension SequenceType {
/// Returns the first element where `predicate` returns `true`, or `nil`
/// if such value is not found.
public func find(@noescape predicate: (Self.Generator.Element) throws -> Bool) rethrows -> Self.Generator.Element? {
for elt in self {
if try predicate(elt) {
return elt
}
}
return nil
}
}-Kevin Ballard
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--
-Dave
We should add the full collection of ruby methods http://matthewcarriere.com/06/23/using-select-reject-collect-inject-and-detect/
We already have them. Well, almost:
select - this is filter reject - this is just filter with a negated
predicate collect - this is map inject - this is reduce detect - this is
the find() method that I'm proposing here.
-Kevin
+1. We've added an extension for this and find it very useful. On
Tue, Dec 29, 2015 at 18:38 Kevin Ballard via swift-evolution <swift-__
I'm proposing a new extension method on SequenceType called find().
It's similar to CollectionType.indexOf() except it returns the
element:extensionSequenceType {
/// Returns the first element where `predicate` returns `true`,
or `nil`
/// if such value is not found.
public func find(@noescape predicate: (Self.Generator.Element)
throws -> Bool) rethrows -> Self.Generator.Element? {
for elt in self {
if try predicate(elt) {
return elt
}
}
return nil
}
}
-Kevin Ballard
_______________________________________________
swift-evolution mailing list
On Wed, Dec 30, 2015, at 02:13 AM, James Campbell wrote:
On 30 Dec 2015, at 02:40, Keith Smiley via swift-evolution <swift- > evolution@swift.org> wrote:
evolution@swift.org> wrote:
swift-evolution@swift.org
https://lists.swift.org/mailman/listinfo/swift-evolution_______________________________________________
swift-evolution mailing list swift-evolution@swift.org
https://lists.swift.org/mailman/listinfo/swift-evolution
+1 on this.
I see a lot of code like this:
sequence.filter(predicate).first
Which is of course is inefficient. However, the go-to optimisation:
sequence.lazy.filter(predicate).first
Is not necessarily better, and has some strange behaviour:
let array = [1, 2, 3, 4, 5, 6]
func noisyPredicate(n: Int) -> Bool {
print(n, terminator: " ")
return n > 2
}
array.lazy.filter(noisyPredicate).first
// 1 2 3 1 2 3
AnySequence(array).lazy.filter(noisyPredicate).first
// 1 2 3 4 5 6
If it’s called on a collection, the collection is only evaluated up until the element being looked for, but it’s done twice. If it’s called on a sequence, the whole sequence is evaluated, regardless of where the element is found.
I think that find is maybe not the best name, though. It’s not immediately clear that it doesn’t return an index. I’d prefer to call it first, as in:
extension SequenceType {
/// Returns the first element where `predicate` returns `true`, or `nil`
/// if such value is not found.
public func first(@noescape thatSatisfies: (Self.Generator.Element) throws -> Bool) rethrows -> Self.Generator.Element? {
for elt in self {
if try thatSatisfies(elt) {
return elt
}
}
return nil
}
}
[1, 2, 3, 4, 5].first(thatSatisfies: (Int) throws -> Bool)
[1, 2, 3, 4, 5].first { $0 > 3 }
On 30 Dec 2015, at 10:13, James Campbell via swift-evolution <swift-evolution@swift.org> wrote:
We should add the full collection of ruby methods http://matthewcarriere.com/06/23/using-select-reject-collect-inject-and-detect/
Sent from my iPhone
On 30 Dec 2015, at 02:40, Keith Smiley via swift-evolution <swift-evolution@swift.org <mailto:swift-evolution@swift.org>> wrote:
+1. We've added an extension for this and find it very useful.
On Tue, Dec 29, 2015 at 18:38 Kevin Ballard via swift-evolution <swift-evolution@swift.org <mailto:swift-evolution@swift.org>> wrote:
I'm proposing a new extension method on SequenceType called find(). It's similar to CollectionType.indexOf() except it returns the element:extension SequenceType {
/// Returns the first element where `predicate` returns `true`, or `nil`
/// if such value is not found.
public func find(@noescape predicate: (Self.Generator.Element) throws -> Bool) rethrows -> Self.Generator.Element? {
for elt in self {
if try predicate(elt) {
return elt
}
}
return nil
}
}-Kevin Ballard
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Good thought, but I doubt such a method would pull its own weight.
-Kevin Ballard
Is it worth considering a version that returns a tuple of (index,
element) ?Nevin
+1. We've added an extension for this and find it very useful. On
Tue, Dec 29, 2015 at 18:38 Kevin Ballard via swift-evolution <swift-__
I'm proposing a new extension method on SequenceType called find().
It's similar to CollectionType.indexOf() except it returns the
element:extensionSequenceType {
/// Returns the first element where `predicate` returns `true`,
or `nil`
/// if such value is not found.
public func find(@noescape predicate: (Self.Generator.Element)
throws -> Bool) rethrows -> Self.Generator.Element? {
for elt in self {
if try predicate(elt) {
return elt
}
}
return nil
}
}
-Kevin Ballard
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On Wed, Dec 30, 2015, at 04:24 PM, Nevin Brackett-Rozinsky wrote:
On Tue, Dec 29, 2015 at 9:40 PM, Keith Smiley via swift-evolution <swift- > evolution@swift.org> wrote:
evolution@swift.org> wrote:
swift-evolution@swift.org
https://lists.swift.org/mailman/listinfo/swift-evolution
I think
subviews.find{ ($0 as? NSButton)?.state == NSOnState } as? NSButton
is sufficient and makes it clear that you are searching for a specific type. Even though you have to cast twice I don't think an additional method would be worth its use since it isn't used as often.
- Maximilian
Am 17.02.2016 um 10:32 schrieb Marco Masser via swift-evolution <swift-evolution@swift.org>:
I just saw this PR and have a quick comment about the implementation: It could be shortened by a few lines using a where clause like this:
func find(@noescape predicate: Self.Generator.Element throws -> Bool) rethrows -> Self.Generator.Element? {
for element in self where try predicate(element) {
return element
}
return nil
}Also, I’d like suggest adding a variant that works better with heterogenous sequences, but I’ll raise that when this proposal goes into review.
FYI: That variant would look like this:
func find<T>(_: T.Type, @noescape matching predicate: T throws -> Bool) rethrows -> T?A question by me on the swift-users mailing list describes its intention, implementation, and usage:
[swift-users] Which is the more idiomatic approach for pinning down the type of a generic parameter?Cheers,
Marco
On 2016-01-10, at 01:58, Kevin Ballard via swift-evolution <swift-evolution@swift.org> wrote:
Proposal PR submitted as Proposal: Add function SequenceType.find(_:) by lilyball · Pull Request #94 · apple/swift-evolution · GitHub
-Kevin Ballard
On Tue, Dec 29, 2015, at 06:38 PM, Kevin Ballard wrote:
I'm proposing a new extension method on SequenceType called find(). It's similar to CollectionType.indexOf() except it returns the element:extensionSequenceType {
/// Returns the first element where `predicate` returns `true`, or `nil`
/// if such value is not found.
public func find(@noescape predicate: (Self.Generator.Element) throws -> Bool) rethrows -> Self.Generator.Element? {
for elt in self {
if try predicate(elt) {
return elt
}
}
return nil
}
}-Kevin Ballard
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+1 on this.
I see a lot of code like this:
sequence.filter(predicate).first
Which is of course is inefficient. However, the go-to optimisation:
sequence.lazy.filter(predicate).first
Is not necessarily better, and has some strange behaviour:
let array = [1, 2, 3, 4, 5, 6] func noisyPredicate(n: Int) -> Bool {
print(n, terminator: " ") return n > 2 }array.lazy.filter(noisyPredicate).first // 1 2 3 1 2 3
AnySequence(array).lazy.filter(noisyPredicate).first // 1 2 3 4 5 6
If it’s called on a collection, the collection is only evaluated up
until the element being looked for, but it’s done twice. If it’s
called on a sequence, the *whole* sequence is evaluated, regardless of
where the element is found.
Actually, you're calling it on a collection in both cases. SequenceType
doesn't have a `first` property (honestly, I think it should). Saying
`lazy.filter(noisyPredicate)` is actually resolving to the version of
filter() from SequenceType, the one that returns an Array, because the
one from LazySequenceType that returns a LazyFilterSequence doesn't have
a `first` property.
As for it calling it twice on a collection, this is because it's
implemented as `isEmpty ? nil : self[startIndex]`, which is honestly
pretty silly.
FWIW, there's other sequence methods that actually evaluate lazy
collections twice, because they detect that the receiver is a
collection and run a preprocessing pass first. For example, the
version of joinWithSeparator() that returns a String does this (to
size all of the elements so it can preallocate a buffer), which causes
duplicate evaluation of lazy filter/map collections. I filed this a
while ago as SR-68[1].
I think that find is maybe not the best name, though. It’s not
immediately clear that it doesn’t return an index.
indexOf() used to be called find(), but it was renamed because find()
didn't make it obvious that it returned an index. I know I personally
got confused all the time about what find() returned.
Also, this is a sequence method. Sequences don't have indexes.
-Kevin Ballard
I’d prefer to call it first, as in:
extensionSequenceType { /// Returns the first element where
`predicate` returns `true`, or `nil` /// if such value is not found.
public func first(@noescape thatSatisfies: (Self.Generator.Element)
throws -> Bool) rethrows -> Self.Generator.Element? { for elt in self
{ if try thatSatisfies(elt) { return elt } } returnnil } }[1, 2, 3, 4, 5].first(thatSatisfies: (Int) throws -> Bool)
[1, 2, 3, 4, 5].first { $0 > 3 }
We should add the full collection of ruby methods
http://matthewcarriere.com/06/23/using-select-reject-collect-inject-and-detect/Sent from my iPhone
+1. We've added an extension for this and find it very useful. On
Tue, Dec 29, 2015 at 18:38 Kevin Ballard via swift-evolution <swift-__
I'm proposing a new extension method on SequenceType called find().
It's similar to CollectionType.indexOf() except it returns the
element:extensionSequenceType{ /// Returns the first element where
`predicate` returns `true`, or `nil` /// if such value is not
found. publicfuncfind(@noescapepredicate: (Self.Generator.Element)throws->Bool)rethrows-
>Self.Generator.Element? { foreltinself{ iftrypredicate(elt) {
returnelt } } returnnil } }-Kevin Ballard
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Links:
On Wed, Dec 30, 2015, at 07:33 AM, Donnacha Oisín Kidney via swift-evolution wrote:
On 30 Dec 2015, at 10:13, James Campbell via swift-evolution <swift- >> evolution@swift.org> wrote:
On 30 Dec 2015, at 02:40, Keith Smiley via swift-evolution <swift- >> evolution@swift.org> wrote:evolution@swift.org> wrote:
Ruby calls that method detect. As in detect and return the item that matches this condition
Sent from my iPhone
On 30 Dec 2015, at 15:33, Donnacha Oisín Kidney <oisin.kidney@gmail.com> wrote:
+1 on this.
I see a lot of code like this:
sequence.filter(predicate).first
Which is of course is inefficient. However, the go-to optimisation:
sequence.lazy.filter(predicate).first
Is not necessarily better, and has some strange behaviour:
let array = [1, 2, 3, 4, 5, 6]
func noisyPredicate(n: Int) -> Bool {
print(n, terminator: " ")
return n > 2
}array.lazy.filter(noisyPredicate).first
// 1 2 3 1 2 3AnySequence(array).lazy.filter(noisyPredicate).first
// 1 2 3 4 5 6If it’s called on a collection, the collection is only evaluated up until the element being looked for, but it’s done twice. If it’s called on a sequence, the whole sequence is evaluated, regardless of where the element is found.
I think that find is maybe not the best name, though. It’s not immediately clear that it doesn’t return an index. I’d prefer to call it first, as in:
extension SequenceType {
/// Returns the first element where `predicate` returns `true`, or `nil`
/// if such value is not found.
public func first(@noescape thatSatisfies: (Self.Generator.Element) throws -> Bool) rethrows -> Self.Generator.Element? {
for elt in self {
if try thatSatisfies(elt) {
return elt
}
}
return nil
}
}[1, 2, 3, 4, 5].first(thatSatisfies: (Int) throws -> Bool)
[1, 2, 3, 4, 5].first { $0 > 3 }
On 30 Dec 2015, at 10:13, James Campbell via swift-evolution <swift-evolution@swift.org> wrote:
We should add the full collection of ruby methods http://matthewcarriere.com/06/23/using-select-reject-collect-inject-and-detect/
Sent from my iPhone
On 30 Dec 2015, at 02:40, Keith Smiley via swift-evolution <swift-evolution@swift.org> wrote:
+1. We've added an extension for this and find it very useful.
On Tue, Dec 29, 2015 at 18:38 Kevin Ballard via swift-evolution <swift-evolution@swift.org> wrote:
I'm proposing a new extension method on SequenceType called find(). It's similar to CollectionType.indexOf() except it returns the element:extension SequenceType {
/// Returns the first element where `predicate` returns `true`, or `nil`
/// if such value is not found.
public func find(@noescape predicate: (Self.Generator.Element) throws -> Bool) rethrows -> Self.Generator.Element? {
for elt in self {
if try predicate(elt) {
return elt
}
}
return nil
}
}-Kevin Ballard
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But overloading the first method with a closure is a clever ide s
Sent from my iPhone
On 30 Dec 2015, at 15:33, Donnacha Oisín Kidney <oisin.kidney@gmail.com> wrote:
+1 on this.
I see a lot of code like this:
sequence.filter(predicate).first
Which is of course is inefficient. However, the go-to optimisation:
sequence.lazy.filter(predicate).first
Is not necessarily better, and has some strange behaviour:
let array = [1, 2, 3, 4, 5, 6]
func noisyPredicate(n: Int) -> Bool {
print(n, terminator: " ")
return n > 2
}array.lazy.filter(noisyPredicate).first
// 1 2 3 1 2 3AnySequence(array).lazy.filter(noisyPredicate).first
// 1 2 3 4 5 6If it’s called on a collection, the collection is only evaluated up until the element being looked for, but it’s done twice. If it’s called on a sequence, the whole sequence is evaluated, regardless of where the element is found.
I think that find is maybe not the best name, though. It’s not immediately clear that it doesn’t return an index. I’d prefer to call it first, as in:
extension SequenceType {
/// Returns the first element where `predicate` returns `true`, or `nil`
/// if such value is not found.
public func first(@noescape thatSatisfies: (Self.Generator.Element) throws -> Bool) rethrows -> Self.Generator.Element? {
for elt in self {
if try thatSatisfies(elt) {
return elt
}
}
return nil
}
}[1, 2, 3, 4, 5].first(thatSatisfies: (Int) throws -> Bool)
[1, 2, 3, 4, 5].first { $0 > 3 }
On 30 Dec 2015, at 10:13, James Campbell via swift-evolution <swift-evolution@swift.org> wrote:
We should add the full collection of ruby methods http://matthewcarriere.com/06/23/using-select-reject-collect-inject-and-detect/
Sent from my iPhone
On 30 Dec 2015, at 02:40, Keith Smiley via swift-evolution <swift-evolution@swift.org> wrote:
+1. We've added an extension for this and find it very useful.
On Tue, Dec 29, 2015 at 18:38 Kevin Ballard via swift-evolution <swift-evolution@swift.org> wrote:
I'm proposing a new extension method on SequenceType called find(). It's similar to CollectionType.indexOf() except it returns the element:extension SequenceType {
/// Returns the first element where `predicate` returns `true`, or `nil`
/// if such value is not found.
public func find(@noescape predicate: (Self.Generator.Element) throws -> Bool) rethrows -> Self.Generator.Element? {
for elt in self {
if try predicate(elt) {
return elt
}
}
return nil
}
}-Kevin Ballard
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Alternatively you can write
subviews.lazy.flatMap({ $0 as? NSButton }).find({ $0.state ==
NSOnState })
-Kevin Ballard
On Wed, Feb 17, 2016, at 07:12 AM, Maximilian Hünenberger via swift-evolution wrote:
I think
subviews.find{ ($0 as? NSButton)?.state == NSOnState } as? NSButton
is sufficient and makes it clear that you are searching for a specific
type. Even though you have to cast twice I don't think an additional
method would be worth its use since it isn't used as often.- Maximilian
Am 17.02.2016 um 10:32 schrieb Marco Masser via swift-evolution <swift- > evolution@swift.org>:
I just saw this PR and have a quick comment about the implementation:
It could be shortened by a few lines using a where clause like this:func find(@noescape predicate: Self.Generator.Elementthrows -> Bool)
rethrows -> Self.Generator.Element? { for element inselfwheretry
predicate(element) { return element } returnnil }Also, I’d like suggest adding a variant that works better with
heterogenous sequences, but I’ll raise that when this proposal goes
into review.FYI: That variant would look like this: func find<T>(_: T.Type,
@noescape matching predicate: Tthrows -> Bool) rethrows -> T?A question by me on the swift-users mailing list describes its
intention, implementation, and usage: [swift-users] Which is the more
idiomatic approach for pinning down the type of a generic
parameter?[1]Cheers,
Marco
On 2016-01-10, at 01:58, Kevin Ballard via swift-evolution <swift- >>> evolution@swift.org> wrote:
Proposal PR submitted as
Proposal: Add function SequenceType.find(_:) by lilyball · Pull Request #94 · apple/swift-evolution · GitHub-Kevin Ballard
On Tue, Dec 29, 2015, at 06:38 PM, Kevin Ballard wrote:
I'm proposing a new extension method on SequenceType called find().
It's similar to CollectionType.indexOf() except it returns the
element:extensionSequenceType { /// Returns the first element where
`predicate` returns `true`, or `nil` /// if such value is not
found. public func find(@noescape predicate:
(Self.Generator.Element) throws -> Bool) rethrows ->
Self.Generator.Element? { for elt in self { if try predicate(elt) {
return elt } } return nil } }-Kevin Ballard
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1. [swift-users] Which is the more idiomatic approach for pinning down the type of a generic parameter?
While I very much prefer the version without any casts, I suspect that you’re right in that the consensus will probably be that adding an additional method for heterogenous sequences will be considered not to be worthwhile. But maybe I’m wrong and if not, I can still keep my own implementation.
Cheers,
Marco
On 2016-02-17, at 16:12, Maximilian Hünenberger <m.huenenberger@me.com> wrote:
I think
subviews.find{ ($0 as? NSButton)?.state == NSOnState } as? NSButton
is sufficient and makes it clear that you are searching for a specific type. Even though you have to cast twice I don't think an additional method would be worth its use since it isn't used as often.
Just to reiterate my point: I very much prefer the version without any casts. I just think this is much clearer and doesn’t put the burden of thinking about accidental memory and speed overhead (when forgetting the “lazy”) on the caller every time:
subviews.find(NSButton.self, matching: { $0.state == NSOnState })
Also, there’s the goal of Swift being easy to learn. Which line do you think is easier to explain to newcomers?
On 2016-02-18, at 00:46, Kevin Ballard via swift-evolution <swift-evolution@swift.org> wrote:
Alternatively you can write
subviews.lazy.flatMap({ $0 as? NSButton }).find({ $0.state == NSOnState })
I would prefer a label on the first parameter, since you're not finding the
NSButton type but instead elements having the type of NSButton.
subviews.find(havingType: NSButton.self, matching: { $0.state == NSOnState
})
On Thu, Feb 18, 2016 at 4:37 AM, Marco Masser via swift-evolution < swift-evolution@swift.org> wrote:
On 2016-02-18, at 00:46, Kevin Ballard via swift-evolution < > swift-evolution@swift.org> wrote:
Alternatively you can write
subviews.lazy.flatMap({ $0 as? NSButton }).find({ $0.state ==
NSOnState })Just to reiterate my point: I very much prefer the version without any
casts. I just think this is much clearer and doesn’t put the burden of
thinking about accidental memory and speed overhead (when forgetting the
“lazy”) on the caller every time:subviews.find(NSButton.self, matching: { $0.state == NSOnState })
Also, there’s the goal of Swift being easy to learn. Which line do you
think is easier to explain to newcomers?_______________________________________________
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