What should a find function return in failure result?
The question has been bothering me since I first realized the List class, where I needed a method to find nodes which data is equal to input value. If ==, then, obviously, return immediately. But otherwise? What should it do then?
I thought about throwing an exception, but how the program will behave when from the function call it will recognizes the failure?
Node* find_node(const T &data) {
if (is_empty())
std::exit(1);
Node *temp = _head;
while (temp != nullptr) {
if (temp->_data == data)
break;
temp = temp->_next;
}
return temp;
}
Well, I kind kind of expect it to return a pointer to a node if search succeeded, so I could access its value in function's call if needed.
c++ function return
asked Dec 31 '18 at 17:02
xt1zerxt1zer
11
|
show 3 more comments
The question has been bothering me since I first realized the List class, where I needed a method to find nodes which data is equal to input value. If ==, then, obviously, return immediately. But otherwise? What should it do then?
I thought about throwing an exception, but how the program will behave when from the function call it will recognizes the failure?
Node* find_node(const T &data) {
if (is_empty())
std::exit(1);
Node *temp = _head;
while (temp != nullptr) {
if (temp->_data == data)
break;
temp = temp->_next;
}
return temp;
}
Well, I kind kind of expect it to return a pointer to a node if search succeeded, so I could access its value in function's call if needed.
c++ function return
asked Dec 31 '18 at 17:02
xt1zerxt1zer
11
4
For a function that returns a pointer, when it fails it's common to return a null pointer. Which of course needs to be checked for.
– Some programmer dude
Dec 31 '18 at 17:04
3
It is already returningnullptr. Seems ok.
– Johnny Mopp
Dec 31 '18 at 17:05
1
It might be interesting to use this pattern: en.wikipedia.org/wiki/Option_type
– Cristiano
Dec 31 '18 at 17:06
3
Calling exit() if the list is empty is not a good idea.
– Neil Butterworth
Dec 31 '18 at 17:08
@NeilButterworth Sorry, I haven't touched this project in weeks. Will it be okay to return nullptr then?
– xt1zer
Dec 31 '18 at 17:10
|
show 3 more comments
The question has been bothering me since I first realized the List class, where I needed a method to find nodes which data is equal to input value. If ==, then, obviously, return immediately. But otherwise? What should it do then?
I thought about throwing an exception, but how the program will behave when from the function call it will recognizes the failure?
Node* find_node(const T &data) {
if (is_empty())
std::exit(1);
Node *temp = _head;
while (temp != nullptr) {
if (temp->_data == data)
break;
temp = temp->_next;
}
return temp;
}
Well, I kind kind of expect it to return a pointer to a node if search succeeded, so I could access its value in function's call if needed.
c++ function return
asked Dec 31 '18 at 17:02
xt1zerxt1zer
11
The question has been bothering me since I first realized the List class, where I needed a method to find nodes which data is equal to input value. If ==, then, obviously, return immediately. But otherwise? What should it do then?
I thought about throwing an exception, but how the program will behave when from the function call it will recognizes the failure?
Node* find_node(const T &data) {
if (is_empty())
std::exit(1);
Node *temp = _head;
while (temp != nullptr) {
if (temp->_data == data)
break;
temp = temp->_next;
}
return temp;
}
Well, I kind kind of expect it to return a pointer to a node if search succeeded, so I could access its value in function's call if needed.
c++ function return
c++ function return
asked Dec 31 '18 at 17:02
xt1zerxt1zer
11
asked Dec 31 '18 at 17:02
xt1zerxt1zer
11
asked Dec 31 '18 at 17:02
xt1zerxt1zer
11
asked Dec 31 '18 at 17:02
xt1zerxt1zer
11
asked Dec 31 '18 at 17:02
xt1zerxt1zer
11
11
4
For a function that returns a pointer, when it fails it's common to return a null pointer. Which of course needs to be checked for.
– Some programmer dude
Dec 31 '18 at 17:04
3
It is already returningnullptr. Seems ok.
– Johnny Mopp
Dec 31 '18 at 17:05
1
It might be interesting to use this pattern: en.wikipedia.org/wiki/Option_type
– Cristiano
Dec 31 '18 at 17:06
3
Calling exit() if the list is empty is not a good idea.
– Neil Butterworth
Dec 31 '18 at 17:08
@NeilButterworth Sorry, I haven't touched this project in weeks. Will it be okay to return nullptr then?
– xt1zer
Dec 31 '18 at 17:10
|
show 3 more comments
4
For a function that returns a pointer, when it fails it's common to return a null pointer. Which of course needs to be checked for.
– Some programmer dude
Dec 31 '18 at 17:04
3
It is already returningnullptr. Seems ok.
– Johnny Mopp
Dec 31 '18 at 17:05
1
It might be interesting to use this pattern: en.wikipedia.org/wiki/Option_type
– Cristiano
Dec 31 '18 at 17:06
3
Calling exit() if the list is empty is not a good idea.
– Neil Butterworth
Dec 31 '18 at 17:08
@NeilButterworth Sorry, I haven't touched this project in weeks. Will it be okay to return nullptr then?
– xt1zer
Dec 31 '18 at 17:10
4
4
For a function that returns a pointer, when it fails it's common to return a null pointer. Which of course needs to be checked for.
– Some programmer dude
Dec 31 '18 at 17:04
For a function that returns a pointer, when it fails it's common to return a null pointer. Which of course needs to be checked for.
– Some programmer dude
Dec 31 '18 at 17:04
3
3
It is already returning
nullptr. Seems ok.– Johnny Mopp
Dec 31 '18 at 17:05
It is already returning
nullptr. Seems ok.– Johnny Mopp
Dec 31 '18 at 17:05
1
1
It might be interesting to use this pattern: en.wikipedia.org/wiki/Option_type
– Cristiano
Dec 31 '18 at 17:06
It might be interesting to use this pattern: en.wikipedia.org/wiki/Option_type
– Cristiano
Dec 31 '18 at 17:06
3
3
Calling exit() if the list is empty is not a good idea.
– Neil Butterworth
Dec 31 '18 at 17:08
Calling exit() if the list is empty is not a good idea.
– Neil Butterworth
Dec 31 '18 at 17:08
@NeilButterworth Sorry, I haven't touched this project in weeks. Will it be okay to return nullptr then?
– xt1zer
Dec 31 '18 at 17:10
@NeilButterworth Sorry, I haven't touched this project in weeks. Will it be okay to return nullptr then?
– xt1zer
Dec 31 '18 at 17:10
|
show 3 more comments
2 Answers
2
active
oldest
votes
nullptr is the correct return value for when the search fails. This is the advantage of using a pointer rather than a reference, as you could return a reference if you knew that you were always going to have a value.
The calling code should always check for nullptr when receiving a pointer from the function call, and handle the fact that the search failed.
The C++ Core Guidelines state, in F.60:
Prefer T* over T& when "no argument" is a valid option
A pointer (T*) can be a nullptr and a reference (T&) cannot, there is no valid "null reference". Sometimes having nullptr as an alternative to indicated "no object" is useful, but if it is not, a reference is notationally simpler and might yield better code.
answered Dec 31 '18 at 17:13
rsjaffersjaffe
3,90171631
add a comment |
There are a number of common ways of handling this situation. The correct one largely depends on what type of thing you're returning.
- If you're returning an iterator, you normally want to return the "one past the end" iterator that the caller passed to define the range you were searching.
- With pointers you typically return a null pointer (which is what the code in the question actually does, though perhaps you didn't realize that, or have forgotten).
- If you're returning a reference, you have a couple of choices. One it to change the return type from
foo &to anoptional<foo &>. Another is to define a single "null" object, and return a reference to that upon failure.
answered Dec 31 '18 at 17:14
Jerry CoffinJerry Coffin
386k50472911
add a comment |
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2 Answers
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active
oldest
votes
2 Answers
2
active
oldest
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active
oldest
votes
nullptr is the correct return value for when the search fails. This is the advantage of using a pointer rather than a reference, as you could return a reference if you knew that you were always going to have a value.
The calling code should always check for nullptr when receiving a pointer from the function call, and handle the fact that the search failed.
The C++ Core Guidelines state, in F.60:
Prefer T* over T& when "no argument" is a valid option
A pointer (T*) can be a nullptr and a reference (T&) cannot, there is no valid "null reference". Sometimes having nullptr as an alternative to indicated "no object" is useful, but if it is not, a reference is notationally simpler and might yield better code.
answered Dec 31 '18 at 17:13
rsjaffersjaffe
3,90171631
add a comment |
nullptr is the correct return value for when the search fails. This is the advantage of using a pointer rather than a reference, as you could return a reference if you knew that you were always going to have a value.
The calling code should always check for nullptr when receiving a pointer from the function call, and handle the fact that the search failed.
The C++ Core Guidelines state, in F.60:
Prefer T* over T& when "no argument" is a valid option
A pointer (T*) can be a nullptr and a reference (T&) cannot, there is no valid "null reference". Sometimes having nullptr as an alternative to indicated "no object" is useful, but if it is not, a reference is notationally simpler and might yield better code.
answered Dec 31 '18 at 17:13
rsjaffersjaffe
3,90171631
add a comment |
nullptr is the correct return value for when the search fails. This is the advantage of using a pointer rather than a reference, as you could return a reference if you knew that you were always going to have a value.
The calling code should always check for nullptr when receiving a pointer from the function call, and handle the fact that the search failed.
The C++ Core Guidelines state, in F.60:
Prefer T* over T& when "no argument" is a valid option
A pointer (T*) can be a nullptr and a reference (T&) cannot, there is no valid "null reference". Sometimes having nullptr as an alternative to indicated "no object" is useful, but if it is not, a reference is notationally simpler and might yield better code.
answered Dec 31 '18 at 17:13
rsjaffersjaffe
3,90171631
nullptr is the correct return value for when the search fails. This is the advantage of using a pointer rather than a reference, as you could return a reference if you knew that you were always going to have a value.
The calling code should always check for nullptr when receiving a pointer from the function call, and handle the fact that the search failed.
The C++ Core Guidelines state, in F.60:
Prefer T* over T& when "no argument" is a valid option
A pointer (T*) can be a nullptr and a reference (T&) cannot, there is no valid "null reference". Sometimes having nullptr as an alternative to indicated "no object" is useful, but if it is not, a reference is notationally simpler and might yield better code.
answered Dec 31 '18 at 17:13
rsjaffersjaffe
3,90171631
edited Dec 31 '18 at 17:20
answered Dec 31 '18 at 17:13
rsjaffersjaffe
3,90171631
answered Dec 31 '18 at 17:13
rsjaffersjaffe
3,90171631
answered Dec 31 '18 at 17:13
rsjaffersjaffe
3,90171631
3,90171631
add a comment |
add a comment |
There are a number of common ways of handling this situation. The correct one largely depends on what type of thing you're returning.
- If you're returning an iterator, you normally want to return the "one past the end" iterator that the caller passed to define the range you were searching.
- With pointers you typically return a null pointer (which is what the code in the question actually does, though perhaps you didn't realize that, or have forgotten).
- If you're returning a reference, you have a couple of choices. One it to change the return type from
foo &to anoptional<foo &>. Another is to define a single "null" object, and return a reference to that upon failure.
answered Dec 31 '18 at 17:14
Jerry CoffinJerry Coffin
386k50472911
add a comment |
There are a number of common ways of handling this situation. The correct one largely depends on what type of thing you're returning.
- If you're returning an iterator, you normally want to return the "one past the end" iterator that the caller passed to define the range you were searching.
- With pointers you typically return a null pointer (which is what the code in the question actually does, though perhaps you didn't realize that, or have forgotten).
- If you're returning a reference, you have a couple of choices. One it to change the return type from
foo &to anoptional<foo &>. Another is to define a single "null" object, and return a reference to that upon failure.
answered Dec 31 '18 at 17:14
Jerry CoffinJerry Coffin
386k50472911
add a comment |
There are a number of common ways of handling this situation. The correct one largely depends on what type of thing you're returning.
- If you're returning an iterator, you normally want to return the "one past the end" iterator that the caller passed to define the range you were searching.
- With pointers you typically return a null pointer (which is what the code in the question actually does, though perhaps you didn't realize that, or have forgotten).
- If you're returning a reference, you have a couple of choices. One it to change the return type from
foo &to anoptional<foo &>. Another is to define a single "null" object, and return a reference to that upon failure.
answered Dec 31 '18 at 17:14
Jerry CoffinJerry Coffin
386k50472911
There are a number of common ways of handling this situation. The correct one largely depends on what type of thing you're returning.
- If you're returning an iterator, you normally want to return the "one past the end" iterator that the caller passed to define the range you were searching.
- With pointers you typically return a null pointer (which is what the code in the question actually does, though perhaps you didn't realize that, or have forgotten).
- If you're returning a reference, you have a couple of choices. One it to change the return type from
foo &to anoptional<foo &>. Another is to define a single "null" object, and return a reference to that upon failure.
answered Dec 31 '18 at 17:14
Jerry CoffinJerry Coffin
386k50472911
edited Dec 31 '18 at 17:24
answered Dec 31 '18 at 17:14
Jerry CoffinJerry Coffin
386k50472911
answered Dec 31 '18 at 17:14
Jerry CoffinJerry Coffin
386k50472911
answered Dec 31 '18 at 17:14
Jerry CoffinJerry Coffin
386k50472911
386k50472911
add a comment |
add a comment |
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4
For a function that returns a pointer, when it fails it's common to return a null pointer. Which of course needs to be checked for.
– Some programmer dude
Dec 31 '18 at 17:04
3
It is already returning
nullptr. Seems ok.– Johnny Mopp
Dec 31 '18 at 17:05
1
It might be interesting to use this pattern: en.wikipedia.org/wiki/Option_type
– Cristiano
Dec 31 '18 at 17:06
3
Calling exit() if the list is empty is not a good idea.
– Neil Butterworth
Dec 31 '18 at 17:08
@NeilButterworth Sorry, I haven't touched this project in weeks. Will it be okay to return nullptr then?
– xt1zer
Dec 31 '18 at 17:10