How to use reduce function in swift for generic array?
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I have the generic array like this -
let array = arrayOfElements as! [T]
I want to add elements of array using default(reduce) function of swift.
How can I do this?
I am using like below -
let result = array.reduce(0,+)
it shows error ambiguous reference to member '+'
arrays swift generics
edited Nov 23 '18 at 9:16
Dávid Pásztor
23.4k83152
asked Nov 23 '18 at 6:16
surajsuraj
12
|
show 1 more comment
I have the generic array like this -
let array = arrayOfElements as! [T]
I want to add elements of array using default(reduce) function of swift.
How can I do this?
I am using like below -
let result = array.reduce(0,+)
it shows error ambiguous reference to member '+'
arrays swift generics
edited Nov 23 '18 at 9:16
Dávid Pásztor
23.4k83152
asked Nov 23 '18 at 6:16
surajsuraj
12
Have a look at Apple's docs: developer.apple.com/documentation/swift/array/2298686-reduce
– Daniel Springer
Nov 23 '18 at 6:23
Could you describe in detail what you want to achieve? For now, you probably get that error, because the compiler does not know what T is, and if + is appliable to elements of type T. Anyway, that does not look like adding element to the array. It reduces the array to the single value (as the 'reduce' name implies).
– Evgeniy
Nov 23 '18 at 6:25
1
How would you expect the compiler to be able to sum a generic type?
– Leo Dabus
Nov 23 '18 at 6:26
YouTshould have+
– Satish
Nov 23 '18 at 6:26
2
Your generic Type would need to be constrained to the Numeric protocol
– Leo Dabus
Nov 23 '18 at 6:27
|
show 1 more comment
I have the generic array like this -
let array = arrayOfElements as! [T]
I want to add elements of array using default(reduce) function of swift.
How can I do this?
I am using like below -
let result = array.reduce(0,+)
it shows error ambiguous reference to member '+'
arrays swift generics
edited Nov 23 '18 at 9:16
Dávid Pásztor
23.4k83152
asked Nov 23 '18 at 6:16
surajsuraj
12
I have the generic array like this -
let array = arrayOfElements as! [T]
I want to add elements of array using default(reduce) function of swift.
How can I do this?
I am using like below -
let result = array.reduce(0,+)
it shows error ambiguous reference to member '+'
arrays swift generics
arrays swift generics
edited Nov 23 '18 at 9:16
Dávid Pásztor
23.4k83152
asked Nov 23 '18 at 6:16
surajsuraj
12
edited Nov 23 '18 at 9:16
Dávid Pásztor
23.4k83152
asked Nov 23 '18 at 6:16
surajsuraj
12
edited Nov 23 '18 at 9:16
Dávid Pásztor
23.4k83152
edited Nov 23 '18 at 9:16
Dávid Pásztor
23.4k83152
edited Nov 23 '18 at 9:16
Dávid Pásztor
23.4k83152
23.4k83152
asked Nov 23 '18 at 6:16
surajsuraj
12
asked Nov 23 '18 at 6:16
surajsuraj
12
asked Nov 23 '18 at 6:16
surajsuraj
12
12
Have a look at Apple's docs: developer.apple.com/documentation/swift/array/2298686-reduce
– Daniel Springer
Nov 23 '18 at 6:23
Could you describe in detail what you want to achieve? For now, you probably get that error, because the compiler does not know what T is, and if + is appliable to elements of type T. Anyway, that does not look like adding element to the array. It reduces the array to the single value (as the 'reduce' name implies).
– Evgeniy
Nov 23 '18 at 6:25
1
How would you expect the compiler to be able to sum a generic type?
– Leo Dabus
Nov 23 '18 at 6:26
YouTshould have+
– Satish
Nov 23 '18 at 6:26
2
Your generic Type would need to be constrained to the Numeric protocol
– Leo Dabus
Nov 23 '18 at 6:27
|
show 1 more comment
Have a look at Apple's docs: developer.apple.com/documentation/swift/array/2298686-reduce
– Daniel Springer
Nov 23 '18 at 6:23
Could you describe in detail what you want to achieve? For now, you probably get that error, because the compiler does not know what T is, and if + is appliable to elements of type T. Anyway, that does not look like adding element to the array. It reduces the array to the single value (as the 'reduce' name implies).
– Evgeniy
Nov 23 '18 at 6:25
1
How would you expect the compiler to be able to sum a generic type?
– Leo Dabus
Nov 23 '18 at 6:26
YouTshould have+
– Satish
Nov 23 '18 at 6:26
2
Your generic Type would need to be constrained to the Numeric protocol
– Leo Dabus
Nov 23 '18 at 6:27
Have a look at Apple's docs: developer.apple.com/documentation/swift/array/2298686-reduce
– Daniel Springer
Nov 23 '18 at 6:23
Have a look at Apple's docs: developer.apple.com/documentation/swift/array/2298686-reduce
– Daniel Springer
Nov 23 '18 at 6:23
Could you describe in detail what you want to achieve? For now, you probably get that error, because the compiler does not know what T is, and if + is appliable to elements of type T. Anyway, that does not look like adding element to the array. It reduces the array to the single value (as the 'reduce' name implies).
– Evgeniy
Nov 23 '18 at 6:25
Could you describe in detail what you want to achieve? For now, you probably get that error, because the compiler does not know what T is, and if + is appliable to elements of type T. Anyway, that does not look like adding element to the array. It reduces the array to the single value (as the 'reduce' name implies).
– Evgeniy
Nov 23 '18 at 6:25
1
1
How would you expect the compiler to be able to sum a generic type?
– Leo Dabus
Nov 23 '18 at 6:26
How would you expect the compiler to be able to sum a generic type?
– Leo Dabus
Nov 23 '18 at 6:26
You
T should have +– Satish
Nov 23 '18 at 6:26
You
T should have +– Satish
Nov 23 '18 at 6:26
2
2
Your generic Type would need to be constrained to the Numeric protocol
– Leo Dabus
Nov 23 '18 at 6:27
Your generic Type would need to be constrained to the Numeric protocol
– Leo Dabus
Nov 23 '18 at 6:27
|
show 1 more comment
2 Answers
2
active
oldest
votes
How do you know that T is a type that can be added? T can be anything, can't it? What if T is Bool? True and False values can certainly not be added.
To be able to add Ts, the range of possible types for T must be limited. T must conform to the Numeric protocol. Since the Numeric protocol defines a + operator, we can be sure that whatever T is, as long as it conforms to Numeric, it can be added.
You could do something like this:
func sum<T: Numeric>(_ array: [T]) -> T {
return array.reduce(0, +)
}
Or an extension:
extension Sequence where Element : Numeric {
func sum() -> Element {
return reduce(0, +)
}
}
Note that in both cases, I have put a : Numeric constraint.
answered Nov 23 '18 at 6:37
SweeperSweeper
73.4k1075144
add a comment |
You can’t. T can be any type, including types that don’t have the + operator and/or can’t be created from the integer literal 0. Those requirements are provided by the Numeric protocol, so you can define your type parameter as <T: Numeric> to make this work
answered Nov 23 '18 at 6:41
SvenSven
20.5k44568
add a comment |
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2 Answers
2
active
oldest
votes
2 Answers
2
active
oldest
votes
active
oldest
votes
active
oldest
votes
How do you know that T is a type that can be added? T can be anything, can't it? What if T is Bool? True and False values can certainly not be added.
To be able to add Ts, the range of possible types for T must be limited. T must conform to the Numeric protocol. Since the Numeric protocol defines a + operator, we can be sure that whatever T is, as long as it conforms to Numeric, it can be added.
You could do something like this:
func sum<T: Numeric>(_ array: [T]) -> T {
return array.reduce(0, +)
}
Or an extension:
extension Sequence where Element : Numeric {
func sum() -> Element {
return reduce(0, +)
}
}
Note that in both cases, I have put a : Numeric constraint.
answered Nov 23 '18 at 6:37
SweeperSweeper
73.4k1075144
add a comment |
How do you know that T is a type that can be added? T can be anything, can't it? What if T is Bool? True and False values can certainly not be added.
To be able to add Ts, the range of possible types for T must be limited. T must conform to the Numeric protocol. Since the Numeric protocol defines a + operator, we can be sure that whatever T is, as long as it conforms to Numeric, it can be added.
You could do something like this:
func sum<T: Numeric>(_ array: [T]) -> T {
return array.reduce(0, +)
}
Or an extension:
extension Sequence where Element : Numeric {
func sum() -> Element {
return reduce(0, +)
}
}
Note that in both cases, I have put a : Numeric constraint.
answered Nov 23 '18 at 6:37
SweeperSweeper
73.4k1075144
add a comment |
How do you know that T is a type that can be added? T can be anything, can't it? What if T is Bool? True and False values can certainly not be added.
To be able to add Ts, the range of possible types for T must be limited. T must conform to the Numeric protocol. Since the Numeric protocol defines a + operator, we can be sure that whatever T is, as long as it conforms to Numeric, it can be added.
You could do something like this:
func sum<T: Numeric>(_ array: [T]) -> T {
return array.reduce(0, +)
}
Or an extension:
extension Sequence where Element : Numeric {
func sum() -> Element {
return reduce(0, +)
}
}
Note that in both cases, I have put a : Numeric constraint.
answered Nov 23 '18 at 6:37
SweeperSweeper
73.4k1075144
How do you know that T is a type that can be added? T can be anything, can't it? What if T is Bool? True and False values can certainly not be added.
To be able to add Ts, the range of possible types for T must be limited. T must conform to the Numeric protocol. Since the Numeric protocol defines a + operator, we can be sure that whatever T is, as long as it conforms to Numeric, it can be added.
You could do something like this:
func sum<T: Numeric>(_ array: [T]) -> T {
return array.reduce(0, +)
}
Or an extension:
extension Sequence where Element : Numeric {
func sum() -> Element {
return reduce(0, +)
}
}
Note that in both cases, I have put a : Numeric constraint.
answered Nov 23 '18 at 6:37
SweeperSweeper
73.4k1075144
answered Nov 23 '18 at 6:37
SweeperSweeper
73.4k1075144
answered Nov 23 '18 at 6:37
SweeperSweeper
73.4k1075144
answered Nov 23 '18 at 6:37
SweeperSweeper
73.4k1075144
73.4k1075144
add a comment |
add a comment |
You can’t. T can be any type, including types that don’t have the + operator and/or can’t be created from the integer literal 0. Those requirements are provided by the Numeric protocol, so you can define your type parameter as <T: Numeric> to make this work
answered Nov 23 '18 at 6:41
SvenSven
20.5k44568
add a comment |
You can’t. T can be any type, including types that don’t have the + operator and/or can’t be created from the integer literal 0. Those requirements are provided by the Numeric protocol, so you can define your type parameter as <T: Numeric> to make this work
answered Nov 23 '18 at 6:41
SvenSven
20.5k44568
add a comment |
You can’t. T can be any type, including types that don’t have the + operator and/or can’t be created from the integer literal 0. Those requirements are provided by the Numeric protocol, so you can define your type parameter as <T: Numeric> to make this work
answered Nov 23 '18 at 6:41
SvenSven
20.5k44568
You can’t. T can be any type, including types that don’t have the + operator and/or can’t be created from the integer literal 0. Those requirements are provided by the Numeric protocol, so you can define your type parameter as <T: Numeric> to make this work
answered Nov 23 '18 at 6:41
SvenSven
20.5k44568
answered Nov 23 '18 at 6:41
SvenSven
20.5k44568
answered Nov 23 '18 at 6:41
SvenSven
20.5k44568
answered Nov 23 '18 at 6:41
SvenSven
20.5k44568
20.5k44568
add a comment |
add a comment |
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Have a look at Apple's docs: developer.apple.com/documentation/swift/array/2298686-reduce
– Daniel Springer
Nov 23 '18 at 6:23
Could you describe in detail what you want to achieve? For now, you probably get that error, because the compiler does not know what T is, and if + is appliable to elements of type T. Anyway, that does not look like adding element to the array. It reduces the array to the single value (as the 'reduce' name implies).
– Evgeniy
Nov 23 '18 at 6:25
1
How would you expect the compiler to be able to sum a generic type?
– Leo Dabus
Nov 23 '18 at 6:26
You
Tshould have+– Satish
Nov 23 '18 at 6:26
2
Your generic Type would need to be constrained to the Numeric protocol
– Leo Dabus
Nov 23 '18 at 6:27