How to use goto statement in lambda expression C++
Is there any way to use goto statement in lambda expression?
#include <iostream>
int main()
{
auto lambda = () {
goto label;
return;
};
lambda();
return 0;
label:
std::cout << "hello, world!" << std::endl;
}
I want the console to output hello, world!, but the compiler gives an error:
use of undeclared label 'label'
goto label;
^
1 error generated.
c++
asked Dec 17 '18 at 12:24
0x119010x11901
657
add a comment |
Is there any way to use goto statement in lambda expression?
#include <iostream>
int main()
{
auto lambda = () {
goto label;
return;
};
lambda();
return 0;
label:
std::cout << "hello, world!" << std::endl;
}
I want the console to output hello, world!, but the compiler gives an error:
use of undeclared label 'label'
goto label;
^
1 error generated.
c++
asked Dec 17 '18 at 12:24
0x119010x11901
657
7
This code is fairly confusing, you should really avoid usinggotolike that, the odds of nothing going wrong are fairly slim. If you could share what you actually wanted to achieve, we might be able to help with that.
– Qubit
Dec 17 '18 at 12:26
1
What's the problem you're trying to solve with goto inside a lambda?
– Ami Tavory
Dec 17 '18 at 12:28
@Qubit Maybe my example does not convey very well, but whether or not to use goto statement is not the key of this question.
– 0x11901
Dec 18 '18 at 3:18
@0x11901 My point was related more to the fact of even consideringgototo move between functions, think of all the issues that arise from something like this, it would become fairly difficult to keep track of what the code does. Not to mention, you then have a function that never reaches thereturnstatement, which seems to defeat the purpose. So the point was, there should never even be a case where you would want to do this, regardless of whether or not it is possible.
– Qubit
Dec 18 '18 at 8:39
add a comment |
Is there any way to use goto statement in lambda expression?
#include <iostream>
int main()
{
auto lambda = () {
goto label;
return;
};
lambda();
return 0;
label:
std::cout << "hello, world!" << std::endl;
}
I want the console to output hello, world!, but the compiler gives an error:
use of undeclared label 'label'
goto label;
^
1 error generated.
c++
asked Dec 17 '18 at 12:24
0x119010x11901
657
Is there any way to use goto statement in lambda expression?
#include <iostream>
int main()
{
auto lambda = () {
goto label;
return;
};
lambda();
return 0;
label:
std::cout << "hello, world!" << std::endl;
}
I want the console to output hello, world!, but the compiler gives an error:
use of undeclared label 'label'
goto label;
^
1 error generated.
c++
c++
asked Dec 17 '18 at 12:24
0x119010x11901
657
asked Dec 17 '18 at 12:24
0x119010x11901
657
asked Dec 17 '18 at 12:24
0x119010x11901
657
asked Dec 17 '18 at 12:24
0x119010x11901
657
asked Dec 17 '18 at 12:24
0x119010x11901
657
657
7
This code is fairly confusing, you should really avoid usinggotolike that, the odds of nothing going wrong are fairly slim. If you could share what you actually wanted to achieve, we might be able to help with that.
– Qubit
Dec 17 '18 at 12:26
1
What's the problem you're trying to solve with goto inside a lambda?
– Ami Tavory
Dec 17 '18 at 12:28
@Qubit Maybe my example does not convey very well, but whether or not to use goto statement is not the key of this question.
– 0x11901
Dec 18 '18 at 3:18
@0x11901 My point was related more to the fact of even consideringgototo move between functions, think of all the issues that arise from something like this, it would become fairly difficult to keep track of what the code does. Not to mention, you then have a function that never reaches thereturnstatement, which seems to defeat the purpose. So the point was, there should never even be a case where you would want to do this, regardless of whether or not it is possible.
– Qubit
Dec 18 '18 at 8:39
add a comment |
7
This code is fairly confusing, you should really avoid usinggotolike that, the odds of nothing going wrong are fairly slim. If you could share what you actually wanted to achieve, we might be able to help with that.
– Qubit
Dec 17 '18 at 12:26
1
What's the problem you're trying to solve with goto inside a lambda?
– Ami Tavory
Dec 17 '18 at 12:28
@Qubit Maybe my example does not convey very well, but whether or not to use goto statement is not the key of this question.
– 0x11901
Dec 18 '18 at 3:18
@0x11901 My point was related more to the fact of even consideringgototo move between functions, think of all the issues that arise from something like this, it would become fairly difficult to keep track of what the code does. Not to mention, you then have a function that never reaches thereturnstatement, which seems to defeat the purpose. So the point was, there should never even be a case where you would want to do this, regardless of whether or not it is possible.
– Qubit
Dec 18 '18 at 8:39
7
7
This code is fairly confusing, you should really avoid using
goto like that, the odds of nothing going wrong are fairly slim. If you could share what you actually wanted to achieve, we might be able to help with that.– Qubit
Dec 17 '18 at 12:26
This code is fairly confusing, you should really avoid using
goto like that, the odds of nothing going wrong are fairly slim. If you could share what you actually wanted to achieve, we might be able to help with that.– Qubit
Dec 17 '18 at 12:26
1
1
What's the problem you're trying to solve with goto inside a lambda?
– Ami Tavory
Dec 17 '18 at 12:28
What's the problem you're trying to solve with goto inside a lambda?
– Ami Tavory
Dec 17 '18 at 12:28
@Qubit Maybe my example does not convey very well, but whether or not to use goto statement is not the key of this question.
– 0x11901
Dec 18 '18 at 3:18
@Qubit Maybe my example does not convey very well, but whether or not to use goto statement is not the key of this question.
– 0x11901
Dec 18 '18 at 3:18
@0x11901 My point was related more to the fact of even considering
goto to move between functions, think of all the issues that arise from something like this, it would become fairly difficult to keep track of what the code does. Not to mention, you then have a function that never reaches the return statement, which seems to defeat the purpose. So the point was, there should never even be a case where you would want to do this, regardless of whether or not it is possible.– Qubit
Dec 18 '18 at 8:39
@0x11901 My point was related more to the fact of even considering
goto to move between functions, think of all the issues that arise from something like this, it would become fairly difficult to keep track of what the code does. Not to mention, you then have a function that never reaches the return statement, which seems to defeat the purpose. So the point was, there should never even be a case where you would want to do this, regardless of whether or not it is possible.– Qubit
Dec 18 '18 at 8:39
add a comment |
3 Answers
3
active
oldest
votes
You can't use goto to move between functions, and a lambda defines a separate function to it's enclosing scope.
From this reference
The
gotostatement must be in the same function as the label it is referring, it may appear before or after the label.
And the standard, [stmt.goto]
The
gotostatement unconditionally transfers control to the statement labeled by the identifier. The identifier shall be a label located in the current function.
answered Dec 17 '18 at 12:28
CalethCaleth
17k22139
add a comment |
Is there any way to use goto statement in lambda expression?
No. Not to leave the scope of lambda and jump to the enclosing scope. You can only goto a labeled statement inside the lambda, same as if it were any other function.
Having said that, the uses for goto in C++ specifically are few and infrequent. There are other, better, options. I urge you not to reach for goto as the first tool you use.
answered Dec 17 '18 at 12:28
StoryTellerStoryTeller
94.5k12191254
3
Actually I can't come up with a single use case ofgotoin C++. In C, I still use it for error handling from time to time.
– liliscent
Dec 17 '18 at 12:40
3
@liliscent - I can't come up with one either (unless I'm in some sort of overly constraint environment). But I don't want to make an argument out of ignorance by saying there absolutely is no use.
– StoryTeller
Dec 17 '18 at 12:41
1
Some state machines are more clearly coded (and more efficient) using goto instead of other techniques. Some C-based SDKs (even when used with C++... say Carbon for example) use goto as the paradigm for error handling.
– Eljay
Dec 17 '18 at 12:47
1
@liliscent Isn't there one for breaking out of multiple loops? I can't think of a better one if you want to break out of all of them at once (even though most of the time it makes more sense to return, I can see a use there).
– Spitemaster
Dec 17 '18 at 18:53
@Spitemaster you usereturnto break out of a deep loop
– Caleth
Dec 17 '18 at 20:25
|
show 1 more comment
The goto statement transfers control to the location specified by label. The goto statement must be in the same function as the label it is referring, it may appear before or after the label.
You can instead do this:
#include <iostream>
int main()
{
auto lambda = () {
goto label;
return;
label:
std::cout << "hello, world!" << std::endl;
};
lambda();
return 0;
}
And it will print "Hello World". See demo.
answered Dec 17 '18 at 12:28
P.WP.W
11.8k3842
add a comment |
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3 Answers
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active
oldest
votes
3 Answers
3
active
oldest
votes
active
oldest
votes
active
oldest
votes
You can't use goto to move between functions, and a lambda defines a separate function to it's enclosing scope.
From this reference
The
gotostatement must be in the same function as the label it is referring, it may appear before or after the label.
And the standard, [stmt.goto]
The
gotostatement unconditionally transfers control to the statement labeled by the identifier. The identifier shall be a label located in the current function.
answered Dec 17 '18 at 12:28
CalethCaleth
17k22139
add a comment |
You can't use goto to move between functions, and a lambda defines a separate function to it's enclosing scope.
From this reference
The
gotostatement must be in the same function as the label it is referring, it may appear before or after the label.
And the standard, [stmt.goto]
The
gotostatement unconditionally transfers control to the statement labeled by the identifier. The identifier shall be a label located in the current function.
answered Dec 17 '18 at 12:28
CalethCaleth
17k22139
add a comment |
You can't use goto to move between functions, and a lambda defines a separate function to it's enclosing scope.
From this reference
The
gotostatement must be in the same function as the label it is referring, it may appear before or after the label.
And the standard, [stmt.goto]
The
gotostatement unconditionally transfers control to the statement labeled by the identifier. The identifier shall be a label located in the current function.
answered Dec 17 '18 at 12:28
CalethCaleth
17k22139
You can't use goto to move between functions, and a lambda defines a separate function to it's enclosing scope.
From this reference
The
gotostatement must be in the same function as the label it is referring, it may appear before or after the label.
And the standard, [stmt.goto]
The
gotostatement unconditionally transfers control to the statement labeled by the identifier. The identifier shall be a label located in the current function.
answered Dec 17 '18 at 12:28
CalethCaleth
17k22139
answered Dec 17 '18 at 12:28
CalethCaleth
17k22139
answered Dec 17 '18 at 12:28
CalethCaleth
17k22139
answered Dec 17 '18 at 12:28
CalethCaleth
17k22139
17k22139
add a comment |
add a comment |
Is there any way to use goto statement in lambda expression?
No. Not to leave the scope of lambda and jump to the enclosing scope. You can only goto a labeled statement inside the lambda, same as if it were any other function.
Having said that, the uses for goto in C++ specifically are few and infrequent. There are other, better, options. I urge you not to reach for goto as the first tool you use.
answered Dec 17 '18 at 12:28
StoryTellerStoryTeller
94.5k12191254
3
Actually I can't come up with a single use case ofgotoin C++. In C, I still use it for error handling from time to time.
– liliscent
Dec 17 '18 at 12:40
3
@liliscent - I can't come up with one either (unless I'm in some sort of overly constraint environment). But I don't want to make an argument out of ignorance by saying there absolutely is no use.
– StoryTeller
Dec 17 '18 at 12:41
1
Some state machines are more clearly coded (and more efficient) using goto instead of other techniques. Some C-based SDKs (even when used with C++... say Carbon for example) use goto as the paradigm for error handling.
– Eljay
Dec 17 '18 at 12:47
1
@liliscent Isn't there one for breaking out of multiple loops? I can't think of a better one if you want to break out of all of them at once (even though most of the time it makes more sense to return, I can see a use there).
– Spitemaster
Dec 17 '18 at 18:53
@Spitemaster you usereturnto break out of a deep loop
– Caleth
Dec 17 '18 at 20:25
|
show 1 more comment
Is there any way to use goto statement in lambda expression?
No. Not to leave the scope of lambda and jump to the enclosing scope. You can only goto a labeled statement inside the lambda, same as if it were any other function.
Having said that, the uses for goto in C++ specifically are few and infrequent. There are other, better, options. I urge you not to reach for goto as the first tool you use.
answered Dec 17 '18 at 12:28
StoryTellerStoryTeller
94.5k12191254
3
Actually I can't come up with a single use case ofgotoin C++. In C, I still use it for error handling from time to time.
– liliscent
Dec 17 '18 at 12:40
3
@liliscent - I can't come up with one either (unless I'm in some sort of overly constraint environment). But I don't want to make an argument out of ignorance by saying there absolutely is no use.
– StoryTeller
Dec 17 '18 at 12:41
1
Some state machines are more clearly coded (and more efficient) using goto instead of other techniques. Some C-based SDKs (even when used with C++... say Carbon for example) use goto as the paradigm for error handling.
– Eljay
Dec 17 '18 at 12:47
1
@liliscent Isn't there one for breaking out of multiple loops? I can't think of a better one if you want to break out of all of them at once (even though most of the time it makes more sense to return, I can see a use there).
– Spitemaster
Dec 17 '18 at 18:53
@Spitemaster you usereturnto break out of a deep loop
– Caleth
Dec 17 '18 at 20:25
|
show 1 more comment
Is there any way to use goto statement in lambda expression?
No. Not to leave the scope of lambda and jump to the enclosing scope. You can only goto a labeled statement inside the lambda, same as if it were any other function.
Having said that, the uses for goto in C++ specifically are few and infrequent. There are other, better, options. I urge you not to reach for goto as the first tool you use.
answered Dec 17 '18 at 12:28
StoryTellerStoryTeller
94.5k12191254
Is there any way to use goto statement in lambda expression?
No. Not to leave the scope of lambda and jump to the enclosing scope. You can only goto a labeled statement inside the lambda, same as if it were any other function.
Having said that, the uses for goto in C++ specifically are few and infrequent. There are other, better, options. I urge you not to reach for goto as the first tool you use.
answered Dec 17 '18 at 12:28
StoryTellerStoryTeller
94.5k12191254
answered Dec 17 '18 at 12:28
StoryTellerStoryTeller
94.5k12191254
answered Dec 17 '18 at 12:28
StoryTellerStoryTeller
94.5k12191254
answered Dec 17 '18 at 12:28
StoryTellerStoryTeller
94.5k12191254
94.5k12191254
3
Actually I can't come up with a single use case ofgotoin C++. In C, I still use it for error handling from time to time.
– liliscent
Dec 17 '18 at 12:40
3
@liliscent - I can't come up with one either (unless I'm in some sort of overly constraint environment). But I don't want to make an argument out of ignorance by saying there absolutely is no use.
– StoryTeller
Dec 17 '18 at 12:41
1
Some state machines are more clearly coded (and more efficient) using goto instead of other techniques. Some C-based SDKs (even when used with C++... say Carbon for example) use goto as the paradigm for error handling.
– Eljay
Dec 17 '18 at 12:47
1
@liliscent Isn't there one for breaking out of multiple loops? I can't think of a better one if you want to break out of all of them at once (even though most of the time it makes more sense to return, I can see a use there).
– Spitemaster
Dec 17 '18 at 18:53
@Spitemaster you usereturnto break out of a deep loop
– Caleth
Dec 17 '18 at 20:25
|
show 1 more comment
3
Actually I can't come up with a single use case ofgotoin C++. In C, I still use it for error handling from time to time.
– liliscent
Dec 17 '18 at 12:40
3
@liliscent - I can't come up with one either (unless I'm in some sort of overly constraint environment). But I don't want to make an argument out of ignorance by saying there absolutely is no use.
– StoryTeller
Dec 17 '18 at 12:41
1
Some state machines are more clearly coded (and more efficient) using goto instead of other techniques. Some C-based SDKs (even when used with C++... say Carbon for example) use goto as the paradigm for error handling.
– Eljay
Dec 17 '18 at 12:47
1
@liliscent Isn't there one for breaking out of multiple loops? I can't think of a better one if you want to break out of all of them at once (even though most of the time it makes more sense to return, I can see a use there).
– Spitemaster
Dec 17 '18 at 18:53
@Spitemaster you usereturnto break out of a deep loop
– Caleth
Dec 17 '18 at 20:25
3
3
Actually I can't come up with a single use case of
goto in C++. In C, I still use it for error handling from time to time.– liliscent
Dec 17 '18 at 12:40
Actually I can't come up with a single use case of
goto in C++. In C, I still use it for error handling from time to time.– liliscent
Dec 17 '18 at 12:40
3
3
@liliscent - I can't come up with one either (unless I'm in some sort of overly constraint environment). But I don't want to make an argument out of ignorance by saying there absolutely is no use.
– StoryTeller
Dec 17 '18 at 12:41
@liliscent - I can't come up with one either (unless I'm in some sort of overly constraint environment). But I don't want to make an argument out of ignorance by saying there absolutely is no use.
– StoryTeller
Dec 17 '18 at 12:41
1
1
Some state machines are more clearly coded (and more efficient) using goto instead of other techniques. Some C-based SDKs (even when used with C++... say Carbon for example) use goto as the paradigm for error handling.
– Eljay
Dec 17 '18 at 12:47
Some state machines are more clearly coded (and more efficient) using goto instead of other techniques. Some C-based SDKs (even when used with C++... say Carbon for example) use goto as the paradigm for error handling.
– Eljay
Dec 17 '18 at 12:47
1
1
@liliscent Isn't there one for breaking out of multiple loops? I can't think of a better one if you want to break out of all of them at once (even though most of the time it makes more sense to return, I can see a use there).
– Spitemaster
Dec 17 '18 at 18:53
@liliscent Isn't there one for breaking out of multiple loops? I can't think of a better one if you want to break out of all of them at once (even though most of the time it makes more sense to return, I can see a use there).
– Spitemaster
Dec 17 '18 at 18:53
@Spitemaster you use
return to break out of a deep loop– Caleth
Dec 17 '18 at 20:25
@Spitemaster you use
return to break out of a deep loop– Caleth
Dec 17 '18 at 20:25
|
show 1 more comment
The goto statement transfers control to the location specified by label. The goto statement must be in the same function as the label it is referring, it may appear before or after the label.
You can instead do this:
#include <iostream>
int main()
{
auto lambda = () {
goto label;
return;
label:
std::cout << "hello, world!" << std::endl;
};
lambda();
return 0;
}
And it will print "Hello World". See demo.
answered Dec 17 '18 at 12:28
P.WP.W
11.8k3842
add a comment |
The goto statement transfers control to the location specified by label. The goto statement must be in the same function as the label it is referring, it may appear before or after the label.
You can instead do this:
#include <iostream>
int main()
{
auto lambda = () {
goto label;
return;
label:
std::cout << "hello, world!" << std::endl;
};
lambda();
return 0;
}
And it will print "Hello World". See demo.
answered Dec 17 '18 at 12:28
P.WP.W
11.8k3842
add a comment |
The goto statement transfers control to the location specified by label. The goto statement must be in the same function as the label it is referring, it may appear before or after the label.
You can instead do this:
#include <iostream>
int main()
{
auto lambda = () {
goto label;
return;
label:
std::cout << "hello, world!" << std::endl;
};
lambda();
return 0;
}
And it will print "Hello World". See demo.
answered Dec 17 '18 at 12:28
P.WP.W
11.8k3842
The goto statement transfers control to the location specified by label. The goto statement must be in the same function as the label it is referring, it may appear before or after the label.
You can instead do this:
#include <iostream>
int main()
{
auto lambda = () {
goto label;
return;
label:
std::cout << "hello, world!" << std::endl;
};
lambda();
return 0;
}
And it will print "Hello World". See demo.
answered Dec 17 '18 at 12:28
P.WP.W
11.8k3842
answered Dec 17 '18 at 12:28
P.WP.W
11.8k3842
answered Dec 17 '18 at 12:28
P.WP.W
11.8k3842
answered Dec 17 '18 at 12:28
P.WP.W
11.8k3842
11.8k3842
add a comment |
add a comment |
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7
This code is fairly confusing, you should really avoid using
gotolike that, the odds of nothing going wrong are fairly slim. If you could share what you actually wanted to achieve, we might be able to help with that.– Qubit
Dec 17 '18 at 12:26
1
What's the problem you're trying to solve with goto inside a lambda?
– Ami Tavory
Dec 17 '18 at 12:28
@Qubit Maybe my example does not convey very well, but whether or not to use goto statement is not the key of this question.
– 0x11901
Dec 18 '18 at 3:18
@0x11901 My point was related more to the fact of even considering
gototo move between functions, think of all the issues that arise from something like this, it would become fairly difficult to keep track of what the code does. Not to mention, you then have a function that never reaches thereturnstatement, which seems to defeat the purpose. So the point was, there should never even be a case where you would want to do this, regardless of whether or not it is possible.– Qubit
Dec 18 '18 at 8:39