Why does my Hailstone Sequence function using recursion only output two values?
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2
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I have the following code:
fn hailSeq(number: i32) -> Vec<i32> {
let mut vec = Vec::new();
vec.push(number);
if number == 1 {
vec.push(1);
return vec;
}
if number % 2 == 0 {
let num = number / 2;
vec.push(num);
hailSeq(num);
} else {
let num = 3 * number + 1;
vec.push(num);
hailSeq(num);
}
return vec;
}
It calculates the Hailstone sequence and stops at 1. The output should look like this for hailSeq(11):
[11, 34, 17, 52, 26, 13, 40, 20, 10, 5, 16, 8, 4, 2, 1]
However, my output looks like this:
[11, 34]
I am not really sure why this is occurring. Perhaps there is a limit on recursion in Rust that I don't know about, but I'm sure there's probably just an error in my code.
recursion rust
edited Nov 9 at 14:58
Shepmaster
145k11279413
asked Nov 9 at 12:47
SeePlusPlus
375
add a comment |
up vote
2
down vote
favorite
I have the following code:
fn hailSeq(number: i32) -> Vec<i32> {
let mut vec = Vec::new();
vec.push(number);
if number == 1 {
vec.push(1);
return vec;
}
if number % 2 == 0 {
let num = number / 2;
vec.push(num);
hailSeq(num);
} else {
let num = 3 * number + 1;
vec.push(num);
hailSeq(num);
}
return vec;
}
It calculates the Hailstone sequence and stops at 1. The output should look like this for hailSeq(11):
[11, 34, 17, 52, 26, 13, 40, 20, 10, 5, 16, 8, 4, 2, 1]
However, my output looks like this:
[11, 34]
I am not really sure why this is occurring. Perhaps there is a limit on recursion in Rust that I don't know about, but I'm sure there's probably just an error in my code.
recursion rust
edited Nov 9 at 14:58
Shepmaster
145k11279413
asked Nov 9 at 12:47
SeePlusPlus
375
1
Please userustfmtto format your code properly next time. Second, in rust we do not use camelCase, but snake_case, e.g. your function name should be hail_seq. Third, don't use an explicitreturnfor the last statement, that is very unrusty. Just writevec(withouth return and;)
– hellow
Nov 9 at 12:51
1
You may explain or link how to generate a hail sequence.
– hellow
Nov 9 at 12:52
1
The more idiomatic in Rust is to use an iterator.
– Boiethios
Nov 9 at 13:10
The fun is there is an implementation for Rust on the link that I added rosettacode.org/wiki/Hailstone_sequence#Rust ;)
– Stargateur
Nov 9 at 13:10
See also stackoverflow.com/a/52905147/279627
– Sven Marnach
Nov 9 at 13:39
add a comment |
up vote
2
down vote
favorite
up vote
2
down vote
favorite
I have the following code:
fn hailSeq(number: i32) -> Vec<i32> {
let mut vec = Vec::new();
vec.push(number);
if number == 1 {
vec.push(1);
return vec;
}
if number % 2 == 0 {
let num = number / 2;
vec.push(num);
hailSeq(num);
} else {
let num = 3 * number + 1;
vec.push(num);
hailSeq(num);
}
return vec;
}
It calculates the Hailstone sequence and stops at 1. The output should look like this for hailSeq(11):
[11, 34, 17, 52, 26, 13, 40, 20, 10, 5, 16, 8, 4, 2, 1]
However, my output looks like this:
[11, 34]
I am not really sure why this is occurring. Perhaps there is a limit on recursion in Rust that I don't know about, but I'm sure there's probably just an error in my code.
recursion rust
edited Nov 9 at 14:58
Shepmaster
145k11279413
asked Nov 9 at 12:47
SeePlusPlus
375
I have the following code:
fn hailSeq(number: i32) -> Vec<i32> {
let mut vec = Vec::new();
vec.push(number);
if number == 1 {
vec.push(1);
return vec;
}
if number % 2 == 0 {
let num = number / 2;
vec.push(num);
hailSeq(num);
} else {
let num = 3 * number + 1;
vec.push(num);
hailSeq(num);
}
return vec;
}
It calculates the Hailstone sequence and stops at 1. The output should look like this for hailSeq(11):
[11, 34, 17, 52, 26, 13, 40, 20, 10, 5, 16, 8, 4, 2, 1]
However, my output looks like this:
[11, 34]
I am not really sure why this is occurring. Perhaps there is a limit on recursion in Rust that I don't know about, but I'm sure there's probably just an error in my code.
recursion rust
recursion rust
edited Nov 9 at 14:58
Shepmaster
145k11279413
asked Nov 9 at 12:47
SeePlusPlus
375
edited Nov 9 at 14:58
Shepmaster
145k11279413
asked Nov 9 at 12:47
SeePlusPlus
375
edited Nov 9 at 14:58
Shepmaster
145k11279413
edited Nov 9 at 14:58
Shepmaster
145k11279413
edited Nov 9 at 14:58
Shepmaster
145k11279413
145k11279413
asked Nov 9 at 12:47
SeePlusPlus
375
asked Nov 9 at 12:47
SeePlusPlus
375
asked Nov 9 at 12:47
SeePlusPlus
375
375
1
Please userustfmtto format your code properly next time. Second, in rust we do not use camelCase, but snake_case, e.g. your function name should be hail_seq. Third, don't use an explicitreturnfor the last statement, that is very unrusty. Just writevec(withouth return and;)
– hellow
Nov 9 at 12:51
1
You may explain or link how to generate a hail sequence.
– hellow
Nov 9 at 12:52
1
The more idiomatic in Rust is to use an iterator.
– Boiethios
Nov 9 at 13:10
The fun is there is an implementation for Rust on the link that I added rosettacode.org/wiki/Hailstone_sequence#Rust ;)
– Stargateur
Nov 9 at 13:10
See also stackoverflow.com/a/52905147/279627
– Sven Marnach
Nov 9 at 13:39
add a comment |
1
Please userustfmtto format your code properly next time. Second, in rust we do not use camelCase, but snake_case, e.g. your function name should be hail_seq. Third, don't use an explicitreturnfor the last statement, that is very unrusty. Just writevec(withouth return and;)
– hellow
Nov 9 at 12:51
1
You may explain or link how to generate a hail sequence.
– hellow
Nov 9 at 12:52
1
The more idiomatic in Rust is to use an iterator.
– Boiethios
Nov 9 at 13:10
The fun is there is an implementation for Rust on the link that I added rosettacode.org/wiki/Hailstone_sequence#Rust ;)
– Stargateur
Nov 9 at 13:10
See also stackoverflow.com/a/52905147/279627
– Sven Marnach
Nov 9 at 13:39
1
1
Please use
rustfmt to format your code properly next time. Second, in rust we do not use camelCase, but snake_case, e.g. your function name should be hail_seq. Third, don't use an explicit return for the last statement, that is very unrusty. Just write vec (withouth return and ;)– hellow
Nov 9 at 12:51
Please use
rustfmt to format your code properly next time. Second, in rust we do not use camelCase, but snake_case, e.g. your function name should be hail_seq. Third, don't use an explicit return for the last statement, that is very unrusty. Just write vec (withouth return and ;)– hellow
Nov 9 at 12:51
1
1
You may explain or link how to generate a hail sequence.
– hellow
Nov 9 at 12:52
You may explain or link how to generate a hail sequence.
– hellow
Nov 9 at 12:52
1
1
The more idiomatic in Rust is to use an iterator.
– Boiethios
Nov 9 at 13:10
The more idiomatic in Rust is to use an iterator.
– Boiethios
Nov 9 at 13:10
The fun is there is an implementation for Rust on the link that I added rosettacode.org/wiki/Hailstone_sequence#Rust ;)
– Stargateur
Nov 9 at 13:10
The fun is there is an implementation for Rust on the link that I added rosettacode.org/wiki/Hailstone_sequence#Rust ;)
– Stargateur
Nov 9 at 13:10
See also stackoverflow.com/a/52905147/279627
– Sven Marnach
Nov 9 at 13:39
See also stackoverflow.com/a/52905147/279627
– Sven Marnach
Nov 9 at 13:39
add a comment |
1 Answer
1
active
oldest
votes
up vote
3
down vote
accepted
Your problem is not Rust-specific, but a more general problem.
On every call of hailSeq you create a new Vec every time, so that only the first vec (from the first call) would be used and returned, hence the [11, 34] (11 from the third line, 34 from the tenth line).
To fix this you have two options, I will provide one here.
The first one would be to extend the current vec with the returned vec, e.g. myvec.extend_from_slice(&returned_vec).
The second solution involves creating a vec on startup and passing the same instance to every call of the function.
fn hail_seq(number: i32) -> Vec<i32> {
fn inner(number: i32, vec: &mut Vec<i32>) {
vec.push(number);
if number == 1 {
return;
}
if number % 2 == 0 {
let num = number / 2;
inner(num, vec);
} else {
let num = 3 * number + 1;
inner(num, vec);
}
}
let mut v = vec!;
inner(number, &mut v);
v
}
fn main() {
println!("{:?}", hail_seq(11));
}
(playground)
As a side-note: If you know that a number can't be negative, use a u32 instead because you will find errors at compile time instead of runtime.
edited Nov 9 at 15:00
Shepmaster
145k11279413
answered Nov 9 at 12:59
hellow
4,44432042
add a comment |
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1 Answer
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1 Answer
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active
oldest
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active
oldest
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active
oldest
votes
up vote
3
down vote
accepted
Your problem is not Rust-specific, but a more general problem.
On every call of hailSeq you create a new Vec every time, so that only the first vec (from the first call) would be used and returned, hence the [11, 34] (11 from the third line, 34 from the tenth line).
To fix this you have two options, I will provide one here.
The first one would be to extend the current vec with the returned vec, e.g. myvec.extend_from_slice(&returned_vec).
The second solution involves creating a vec on startup and passing the same instance to every call of the function.
fn hail_seq(number: i32) -> Vec<i32> {
fn inner(number: i32, vec: &mut Vec<i32>) {
vec.push(number);
if number == 1 {
return;
}
if number % 2 == 0 {
let num = number / 2;
inner(num, vec);
} else {
let num = 3 * number + 1;
inner(num, vec);
}
}
let mut v = vec!;
inner(number, &mut v);
v
}
fn main() {
println!("{:?}", hail_seq(11));
}
(playground)
As a side-note: If you know that a number can't be negative, use a u32 instead because you will find errors at compile time instead of runtime.
edited Nov 9 at 15:00
Shepmaster
145k11279413
answered Nov 9 at 12:59
hellow
4,44432042
add a comment |
up vote
3
down vote
accepted
Your problem is not Rust-specific, but a more general problem.
On every call of hailSeq you create a new Vec every time, so that only the first vec (from the first call) would be used and returned, hence the [11, 34] (11 from the third line, 34 from the tenth line).
To fix this you have two options, I will provide one here.
The first one would be to extend the current vec with the returned vec, e.g. myvec.extend_from_slice(&returned_vec).
The second solution involves creating a vec on startup and passing the same instance to every call of the function.
fn hail_seq(number: i32) -> Vec<i32> {
fn inner(number: i32, vec: &mut Vec<i32>) {
vec.push(number);
if number == 1 {
return;
}
if number % 2 == 0 {
let num = number / 2;
inner(num, vec);
} else {
let num = 3 * number + 1;
inner(num, vec);
}
}
let mut v = vec!;
inner(number, &mut v);
v
}
fn main() {
println!("{:?}", hail_seq(11));
}
(playground)
As a side-note: If you know that a number can't be negative, use a u32 instead because you will find errors at compile time instead of runtime.
edited Nov 9 at 15:00
Shepmaster
145k11279413
answered Nov 9 at 12:59
hellow
4,44432042
add a comment |
up vote
3
down vote
accepted
up vote
3
down vote
accepted
Your problem is not Rust-specific, but a more general problem.
On every call of hailSeq you create a new Vec every time, so that only the first vec (from the first call) would be used and returned, hence the [11, 34] (11 from the third line, 34 from the tenth line).
To fix this you have two options, I will provide one here.
The first one would be to extend the current vec with the returned vec, e.g. myvec.extend_from_slice(&returned_vec).
The second solution involves creating a vec on startup and passing the same instance to every call of the function.
fn hail_seq(number: i32) -> Vec<i32> {
fn inner(number: i32, vec: &mut Vec<i32>) {
vec.push(number);
if number == 1 {
return;
}
if number % 2 == 0 {
let num = number / 2;
inner(num, vec);
} else {
let num = 3 * number + 1;
inner(num, vec);
}
}
let mut v = vec!;
inner(number, &mut v);
v
}
fn main() {
println!("{:?}", hail_seq(11));
}
(playground)
As a side-note: If you know that a number can't be negative, use a u32 instead because you will find errors at compile time instead of runtime.
edited Nov 9 at 15:00
Shepmaster
145k11279413
answered Nov 9 at 12:59
hellow
4,44432042
Your problem is not Rust-specific, but a more general problem.
On every call of hailSeq you create a new Vec every time, so that only the first vec (from the first call) would be used and returned, hence the [11, 34] (11 from the third line, 34 from the tenth line).
To fix this you have two options, I will provide one here.
The first one would be to extend the current vec with the returned vec, e.g. myvec.extend_from_slice(&returned_vec).
The second solution involves creating a vec on startup and passing the same instance to every call of the function.
fn hail_seq(number: i32) -> Vec<i32> {
fn inner(number: i32, vec: &mut Vec<i32>) {
vec.push(number);
if number == 1 {
return;
}
if number % 2 == 0 {
let num = number / 2;
inner(num, vec);
} else {
let num = 3 * number + 1;
inner(num, vec);
}
}
let mut v = vec!;
inner(number, &mut v);
v
}
fn main() {
println!("{:?}", hail_seq(11));
}
(playground)
As a side-note: If you know that a number can't be negative, use a u32 instead because you will find errors at compile time instead of runtime.
edited Nov 9 at 15:00
Shepmaster
145k11279413
answered Nov 9 at 12:59
hellow
4,44432042
edited Nov 9 at 15:00
Shepmaster
145k11279413
edited Nov 9 at 15:00
Shepmaster
145k11279413
edited Nov 9 at 15:00
Shepmaster
145k11279413
145k11279413
answered Nov 9 at 12:59
hellow
4,44432042
answered Nov 9 at 12:59
hellow
4,44432042
answered Nov 9 at 12:59
hellow
4,44432042
4,44432042
add a comment |
add a comment |
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1
Please use
rustfmtto format your code properly next time. Second, in rust we do not use camelCase, but snake_case, e.g. your function name should be hail_seq. Third, don't use an explicitreturnfor the last statement, that is very unrusty. Just writevec(withouth return and;)– hellow
Nov 9 at 12:51
1
You may explain or link how to generate a hail sequence.
– hellow
Nov 9 at 12:52
1
The more idiomatic in Rust is to use an iterator.
– Boiethios
Nov 9 at 13:10
The fun is there is an implementation for Rust on the link that I added rosettacode.org/wiki/Hailstone_sequence#Rust ;)
– Stargateur
Nov 9 at 13:10
See also stackoverflow.com/a/52905147/279627
– Sven Marnach
Nov 9 at 13:39