Splitting the list in to two parts in Scala
I have a List with n as 3 ls as List(a,b,c,d,e) My query is to code for the (3,List(a,b,c,d,e)) I want to split them in to two parts such as List(a,b,c),List(d,e). For this the scala program is like below.
I don't understand val(pre,post). why it is used and what do we get from it? can someone please elaborate?
def splitRecursive[A](n: Int, ls: List[A]): (List[A], List[A]) = (n, ls) match {
case (_, Nil) => (Nil, Nil)
case (0, list) => (Nil, list)
case (n, h :: tail) => {
val (pre, post) = splitRecursive(n - 1, tail)
(h :: pre, post)
}
}
scala
asked Jan 18 at 23:45
user2708013user2708013
215
add a comment |
I have a List with n as 3 ls as List(a,b,c,d,e) My query is to code for the (3,List(a,b,c,d,e)) I want to split them in to two parts such as List(a,b,c),List(d,e). For this the scala program is like below.
I don't understand val(pre,post). why it is used and what do we get from it? can someone please elaborate?
def splitRecursive[A](n: Int, ls: List[A]): (List[A], List[A]) = (n, ls) match {
case (_, Nil) => (Nil, Nil)
case (0, list) => (Nil, list)
case (n, h :: tail) => {
val (pre, post) = splitRecursive(n - 1, tail)
(h :: pre, post)
}
}
scala
asked Jan 18 at 23:45
user2708013user2708013
215
add a comment |
I have a List with n as 3 ls as List(a,b,c,d,e) My query is to code for the (3,List(a,b,c,d,e)) I want to split them in to two parts such as List(a,b,c),List(d,e). For this the scala program is like below.
I don't understand val(pre,post). why it is used and what do we get from it? can someone please elaborate?
def splitRecursive[A](n: Int, ls: List[A]): (List[A], List[A]) = (n, ls) match {
case (_, Nil) => (Nil, Nil)
case (0, list) => (Nil, list)
case (n, h :: tail) => {
val (pre, post) = splitRecursive(n - 1, tail)
(h :: pre, post)
}
}
scala
asked Jan 18 at 23:45
user2708013user2708013
215
I have a List with n as 3 ls as List(a,b,c,d,e) My query is to code for the (3,List(a,b,c,d,e)) I want to split them in to two parts such as List(a,b,c),List(d,e). For this the scala program is like below.
I don't understand val(pre,post). why it is used and what do we get from it? can someone please elaborate?
def splitRecursive[A](n: Int, ls: List[A]): (List[A], List[A]) = (n, ls) match {
case (_, Nil) => (Nil, Nil)
case (0, list) => (Nil, list)
case (n, h :: tail) => {
val (pre, post) = splitRecursive(n - 1, tail)
(h :: pre, post)
}
}
scala
scala
asked Jan 18 at 23:45
user2708013user2708013
215
asked Jan 18 at 23:45
user2708013user2708013
215
asked Jan 18 at 23:45
user2708013user2708013
215
asked Jan 18 at 23:45
user2708013user2708013
215
asked Jan 18 at 23:45
user2708013user2708013
215
215
add a comment |
add a comment |
1 Answer
1
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Your splitRecursive function returns a pair of lists. To get the two lists out of the pair, you can either fetch them like this:
val result = splitRecursive(n - 1, tail)
val pre = result._1
val post = result._2
Or you can use destructuring to get them without first having to bind the pair to result. That is what the syntax in splitRecursive is doing.
val (pre, post) = splitRecursive(n - 1, tail)
It is simply a convenient way to get the elements out of a pair (or some other structure that can be destructured).
edited Jan 19 at 1:15
SergGr
20.9k22243
answered Jan 18 at 23:58
marstranmarstran
10.1k12441
add a comment |
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1 Answer
1
active
oldest
votes
1 Answer
1
active
oldest
votes
active
oldest
votes
active
oldest
votes
Your splitRecursive function returns a pair of lists. To get the two lists out of the pair, you can either fetch them like this:
val result = splitRecursive(n - 1, tail)
val pre = result._1
val post = result._2
Or you can use destructuring to get them without first having to bind the pair to result. That is what the syntax in splitRecursive is doing.
val (pre, post) = splitRecursive(n - 1, tail)
It is simply a convenient way to get the elements out of a pair (or some other structure that can be destructured).
edited Jan 19 at 1:15
SergGr
20.9k22243
answered Jan 18 at 23:58
marstranmarstran
10.1k12441
add a comment |
Your splitRecursive function returns a pair of lists. To get the two lists out of the pair, you can either fetch them like this:
val result = splitRecursive(n - 1, tail)
val pre = result._1
val post = result._2
Or you can use destructuring to get them without first having to bind the pair to result. That is what the syntax in splitRecursive is doing.
val (pre, post) = splitRecursive(n - 1, tail)
It is simply a convenient way to get the elements out of a pair (or some other structure that can be destructured).
edited Jan 19 at 1:15
SergGr
20.9k22243
answered Jan 18 at 23:58
marstranmarstran
10.1k12441
add a comment |
Your splitRecursive function returns a pair of lists. To get the two lists out of the pair, you can either fetch them like this:
val result = splitRecursive(n - 1, tail)
val pre = result._1
val post = result._2
Or you can use destructuring to get them without first having to bind the pair to result. That is what the syntax in splitRecursive is doing.
val (pre, post) = splitRecursive(n - 1, tail)
It is simply a convenient way to get the elements out of a pair (or some other structure that can be destructured).
edited Jan 19 at 1:15
SergGr
20.9k22243
answered Jan 18 at 23:58
marstranmarstran
10.1k12441
Your splitRecursive function returns a pair of lists. To get the two lists out of the pair, you can either fetch them like this:
val result = splitRecursive(n - 1, tail)
val pre = result._1
val post = result._2
Or you can use destructuring to get them without first having to bind the pair to result. That is what the syntax in splitRecursive is doing.
val (pre, post) = splitRecursive(n - 1, tail)
It is simply a convenient way to get the elements out of a pair (or some other structure that can be destructured).
edited Jan 19 at 1:15
SergGr
20.9k22243
answered Jan 18 at 23:58
marstranmarstran
10.1k12441
edited Jan 19 at 1:15
SergGr
20.9k22243
edited Jan 19 at 1:15
SergGr
20.9k22243
edited Jan 19 at 1:15
SergGr
20.9k22243
20.9k22243
answered Jan 18 at 23:58
marstranmarstran
10.1k12441
answered Jan 18 at 23:58
marstranmarstran
10.1k12441
answered Jan 18 at 23:58
marstranmarstran
10.1k12441
10.1k12441
add a comment |
add a comment |
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