Please how do I make this function Tail-recursive in F#?
let ListtoTuple (lst:'a list) :('a * 'a) list =
let rec loop (lt :'a list) acc =
match lt with
| x:: y :: t-> (x,y):: loop t acc
| _ -> acc
loop lst
Question: ListtoTuple 6 [1..1000000]
I want this kind of result : [(1, 2); (3, 4); (5, 6); (7, 8); (9, 10)...] but I keep getting process is terminated due to StackOverflow. Please, I would like to know if there is anything I am doing wrong.
f# f#-interactive f#-data f#-3.0
asked Nov 12 at 16:40
T.M
389
add a comment |
let ListtoTuple (lst:'a list) :('a * 'a) list =
let rec loop (lt :'a list) acc =
match lt with
| x:: y :: t-> (x,y):: loop t acc
| _ -> acc
loop lst
Question: ListtoTuple 6 [1..1000000]
I want this kind of result : [(1, 2); (3, 4); (5, 6); (7, 8); (9, 10)...] but I keep getting process is terminated due to StackOverflow. Please, I would like to know if there is anything I am doing wrong.
f# f#-interactive f#-data f#-3.0
asked Nov 12 at 16:40
T.M
389
Don't use unrelated tags. It doesn't improve visibility, it only annoys people interested in those tags. As fortail-recursiveit means the recursive call comes last.
– Panagiotis Kanavos
Nov 12 at 16:43
add a comment |
let ListtoTuple (lst:'a list) :('a * 'a) list =
let rec loop (lt :'a list) acc =
match lt with
| x:: y :: t-> (x,y):: loop t acc
| _ -> acc
loop lst
Question: ListtoTuple 6 [1..1000000]
I want this kind of result : [(1, 2); (3, 4); (5, 6); (7, 8); (9, 10)...] but I keep getting process is terminated due to StackOverflow. Please, I would like to know if there is anything I am doing wrong.
f# f#-interactive f#-data f#-3.0
asked Nov 12 at 16:40
T.M
389
let ListtoTuple (lst:'a list) :('a * 'a) list =
let rec loop (lt :'a list) acc =
match lt with
| x:: y :: t-> (x,y):: loop t acc
| _ -> acc
loop lst
Question: ListtoTuple 6 [1..1000000]
I want this kind of result : [(1, 2); (3, 4); (5, 6); (7, 8); (9, 10)...] but I keep getting process is terminated due to StackOverflow. Please, I would like to know if there is anything I am doing wrong.
f# f#-interactive f#-data f#-3.0
f# f#-interactive f#-data f#-3.0
asked Nov 12 at 16:40
T.M
389
asked Nov 12 at 16:40
T.M
389
edited Nov 12 at 16:56
asked Nov 12 at 16:40
T.M
389
asked Nov 12 at 16:40
T.M
389
asked Nov 12 at 16:40
T.M
389
389
Don't use unrelated tags. It doesn't improve visibility, it only annoys people interested in those tags. As fortail-recursiveit means the recursive call comes last.
– Panagiotis Kanavos
Nov 12 at 16:43
add a comment |
Don't use unrelated tags. It doesn't improve visibility, it only annoys people interested in those tags. As fortail-recursiveit means the recursive call comes last.
– Panagiotis Kanavos
Nov 12 at 16:43
Don't use unrelated tags. It doesn't improve visibility, it only annoys people interested in those tags. As for
tail-recursive it means the recursive call comes last.– Panagiotis Kanavos
Nov 12 at 16:43
Don't use unrelated tags. It doesn't improve visibility, it only annoys people interested in those tags. As for
tail-recursive it means the recursive call comes last.– Panagiotis Kanavos
Nov 12 at 16:43
add a comment |
2 Answers
2
active
oldest
votes
Your code is almost correct. The problem is here:
(x,y):: loop f t acc
You are concatenating to the result of loop which means it is not tail recursive because it has to wait for the result of loop to then concatenate.
The key is in the parameter acc which stands for accumulator. That means that is where you need to be concatenating your resulting list, which then gets passed to the next level until there is nothing more to add and then the acc has the completed list which is returned here:
| _ -> acc
answered Nov 12 at 16:57
AMieres
2,050510
Thanks for the explanation AMieres
– T.M
Nov 12 at 17:17
add a comment |
From this thread:
let listToPairList lst =
let rec aux acc lst =
match lst with
| -> acc |> List.rev
| x:: -> (x,x)::acc |> List.rev
| x1::x2::xs -> aux ((x1,x2)::acc) xs
aux lst
answered Nov 12 at 16:55
gileCAD
1,31256
Thank you gileCAD
– T.M
Nov 12 at 17:16
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
Your code is almost correct. The problem is here:
(x,y):: loop f t acc
You are concatenating to the result of loop which means it is not tail recursive because it has to wait for the result of loop to then concatenate.
The key is in the parameter acc which stands for accumulator. That means that is where you need to be concatenating your resulting list, which then gets passed to the next level until there is nothing more to add and then the acc has the completed list which is returned here:
| _ -> acc
answered Nov 12 at 16:57
AMieres
2,050510
Thanks for the explanation AMieres
– T.M
Nov 12 at 17:17
add a comment |
Your code is almost correct. The problem is here:
(x,y):: loop f t acc
You are concatenating to the result of loop which means it is not tail recursive because it has to wait for the result of loop to then concatenate.
The key is in the parameter acc which stands for accumulator. That means that is where you need to be concatenating your resulting list, which then gets passed to the next level until there is nothing more to add and then the acc has the completed list which is returned here:
| _ -> acc
answered Nov 12 at 16:57
AMieres
2,050510
Thanks for the explanation AMieres
– T.M
Nov 12 at 17:17
add a comment |
Your code is almost correct. The problem is here:
(x,y):: loop f t acc
You are concatenating to the result of loop which means it is not tail recursive because it has to wait for the result of loop to then concatenate.
The key is in the parameter acc which stands for accumulator. That means that is where you need to be concatenating your resulting list, which then gets passed to the next level until there is nothing more to add and then the acc has the completed list which is returned here:
| _ -> acc
answered Nov 12 at 16:57
AMieres
2,050510
Your code is almost correct. The problem is here:
(x,y):: loop f t acc
You are concatenating to the result of loop which means it is not tail recursive because it has to wait for the result of loop to then concatenate.
The key is in the parameter acc which stands for accumulator. That means that is where you need to be concatenating your resulting list, which then gets passed to the next level until there is nothing more to add and then the acc has the completed list which is returned here:
| _ -> acc
answered Nov 12 at 16:57
AMieres
2,050510
answered Nov 12 at 16:57
AMieres
2,050510
answered Nov 12 at 16:57
AMieres
2,050510
answered Nov 12 at 16:57
AMieres
2,050510
2,050510
Thanks for the explanation AMieres
– T.M
Nov 12 at 17:17
add a comment |
Thanks for the explanation AMieres
– T.M
Nov 12 at 17:17
Thanks for the explanation AMieres
– T.M
Nov 12 at 17:17
Thanks for the explanation AMieres
– T.M
Nov 12 at 17:17
add a comment |
From this thread:
let listToPairList lst =
let rec aux acc lst =
match lst with
| -> acc |> List.rev
| x:: -> (x,x)::acc |> List.rev
| x1::x2::xs -> aux ((x1,x2)::acc) xs
aux lst
answered Nov 12 at 16:55
gileCAD
1,31256
Thank you gileCAD
– T.M
Nov 12 at 17:16
add a comment |
From this thread:
let listToPairList lst =
let rec aux acc lst =
match lst with
| -> acc |> List.rev
| x:: -> (x,x)::acc |> List.rev
| x1::x2::xs -> aux ((x1,x2)::acc) xs
aux lst
answered Nov 12 at 16:55
gileCAD
1,31256
Thank you gileCAD
– T.M
Nov 12 at 17:16
add a comment |
From this thread:
let listToPairList lst =
let rec aux acc lst =
match lst with
| -> acc |> List.rev
| x:: -> (x,x)::acc |> List.rev
| x1::x2::xs -> aux ((x1,x2)::acc) xs
aux lst
answered Nov 12 at 16:55
gileCAD
1,31256
From this thread:
let listToPairList lst =
let rec aux acc lst =
match lst with
| -> acc |> List.rev
| x:: -> (x,x)::acc |> List.rev
| x1::x2::xs -> aux ((x1,x2)::acc) xs
aux lst
answered Nov 12 at 16:55
gileCAD
1,31256
answered Nov 12 at 16:55
gileCAD
1,31256
answered Nov 12 at 16:55
gileCAD
1,31256
answered Nov 12 at 16:55
gileCAD
1,31256
1,31256
Thank you gileCAD
– T.M
Nov 12 at 17:16
add a comment |
Thank you gileCAD
– T.M
Nov 12 at 17:16
Thank you gileCAD
– T.M
Nov 12 at 17:16
Thank you gileCAD
– T.M
Nov 12 at 17:16
add a comment |
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Don't use unrelated tags. It doesn't improve visibility, it only annoys people interested in those tags. As for
tail-recursiveit means the recursive call comes last.– Panagiotis Kanavos
Nov 12 at 16:43