C++17 Fold Expression not Compiling
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first time posting so sorry if I have poor format. I encountered fold expressions for the first time the other day and am trying to get something up and running with them. However, all of my attempts have failed to compile. I've boiled it down to the following:
//test.cpp
template<typename... types>
auto adder(types&... args){
return (args+...);
}
int main(){return 0;}
And I compiled it with
g++ -std=c++17 test.cpp
And it produces the following errors:
testCode.cpp: In function 'auto adder(types& ...)':
testCode.cpp:5:15: error: expected primary-expression before '...' token
return (args+...);
^
testCode.cpp:5:15: error: expected ')' before '...' token
testCode.cpp:5:18: error: parameter packs not expanded with '...':
return (args+...);
^
testCode.cpp:5:18: note: 'args'
From everything I've seen this should be working, so if someone can tell me what I'm doing wrong I would greatly appreciate it.
I'm working with xenial linux (on a crouton on chrome OS) and a fresh install of g++.
c++ c++17
edited Nov 16 '18 at 23:19
Nicol Bolas
293k34483660
asked Nov 16 '18 at 23:11
BronickiBronicki
261
add a comment |
first time posting so sorry if I have poor format. I encountered fold expressions for the first time the other day and am trying to get something up and running with them. However, all of my attempts have failed to compile. I've boiled it down to the following:
//test.cpp
template<typename... types>
auto adder(types&... args){
return (args+...);
}
int main(){return 0;}
And I compiled it with
g++ -std=c++17 test.cpp
And it produces the following errors:
testCode.cpp: In function 'auto adder(types& ...)':
testCode.cpp:5:15: error: expected primary-expression before '...' token
return (args+...);
^
testCode.cpp:5:15: error: expected ')' before '...' token
testCode.cpp:5:18: error: parameter packs not expanded with '...':
return (args+...);
^
testCode.cpp:5:18: note: 'args'
From everything I've seen this should be working, so if someone can tell me what I'm doing wrong I would greatly appreciate it.
I'm working with xenial linux (on a crouton on chrome OS) and a fresh install of g++.
c++ c++17
edited Nov 16 '18 at 23:19
Nicol Bolas
293k34483660
asked Nov 16 '18 at 23:11
BronickiBronicki
261
Which version of g++ are you using? This should work with current versions of all major compilers (try for yourself here). In the case of g++, it seems to work starting with version 6.1, which is already pretty old (latest version is 8.2). I guess you must be using a really ancient version…
– Michael Kenzel
Nov 16 '18 at 23:23
I think that you edited this code sample. I was trying it out for myself and it broke until I fixed it. And now your code sample works just fine. What did you do?
– Zan Lynx
Nov 16 '18 at 23:28
Certainly works with GCC 8.1.0. crouron on a chromebook is perhaps not the best C++ development environment - much as I like chromebooks.
– Neil Butterworth
Nov 16 '18 at 23:36
Hello all, as Kenzel suspected, this was a versioning issue with the g++ compiler. Not sure what my computer was default installing, but a newer version does fix the problem.
– Bronicki
Nov 17 '18 at 16:45
add a comment |
first time posting so sorry if I have poor format. I encountered fold expressions for the first time the other day and am trying to get something up and running with them. However, all of my attempts have failed to compile. I've boiled it down to the following:
//test.cpp
template<typename... types>
auto adder(types&... args){
return (args+...);
}
int main(){return 0;}
And I compiled it with
g++ -std=c++17 test.cpp
And it produces the following errors:
testCode.cpp: In function 'auto adder(types& ...)':
testCode.cpp:5:15: error: expected primary-expression before '...' token
return (args+...);
^
testCode.cpp:5:15: error: expected ')' before '...' token
testCode.cpp:5:18: error: parameter packs not expanded with '...':
return (args+...);
^
testCode.cpp:5:18: note: 'args'
From everything I've seen this should be working, so if someone can tell me what I'm doing wrong I would greatly appreciate it.
I'm working with xenial linux (on a crouton on chrome OS) and a fresh install of g++.
c++ c++17
edited Nov 16 '18 at 23:19
Nicol Bolas
293k34483660
asked Nov 16 '18 at 23:11
BronickiBronicki
261
first time posting so sorry if I have poor format. I encountered fold expressions for the first time the other day and am trying to get something up and running with them. However, all of my attempts have failed to compile. I've boiled it down to the following:
//test.cpp
template<typename... types>
auto adder(types&... args){
return (args+...);
}
int main(){return 0;}
And I compiled it with
g++ -std=c++17 test.cpp
And it produces the following errors:
testCode.cpp: In function 'auto adder(types& ...)':
testCode.cpp:5:15: error: expected primary-expression before '...' token
return (args+...);
^
testCode.cpp:5:15: error: expected ')' before '...' token
testCode.cpp:5:18: error: parameter packs not expanded with '...':
return (args+...);
^
testCode.cpp:5:18: note: 'args'
From everything I've seen this should be working, so if someone can tell me what I'm doing wrong I would greatly appreciate it.
I'm working with xenial linux (on a crouton on chrome OS) and a fresh install of g++.
c++ c++17
c++ c++17
edited Nov 16 '18 at 23:19
Nicol Bolas
293k34483660
asked Nov 16 '18 at 23:11
BronickiBronicki
261
edited Nov 16 '18 at 23:19
Nicol Bolas
293k34483660
asked Nov 16 '18 at 23:11
BronickiBronicki
261
edited Nov 16 '18 at 23:19
Nicol Bolas
293k34483660
edited Nov 16 '18 at 23:19
Nicol Bolas
293k34483660
edited Nov 16 '18 at 23:19
Nicol Bolas
293k34483660
293k34483660
asked Nov 16 '18 at 23:11
BronickiBronicki
261
asked Nov 16 '18 at 23:11
BronickiBronicki
261
asked Nov 16 '18 at 23:11
BronickiBronicki
261
261
Which version of g++ are you using? This should work with current versions of all major compilers (try for yourself here). In the case of g++, it seems to work starting with version 6.1, which is already pretty old (latest version is 8.2). I guess you must be using a really ancient version…
– Michael Kenzel
Nov 16 '18 at 23:23
I think that you edited this code sample. I was trying it out for myself and it broke until I fixed it. And now your code sample works just fine. What did you do?
– Zan Lynx
Nov 16 '18 at 23:28
Certainly works with GCC 8.1.0. crouron on a chromebook is perhaps not the best C++ development environment - much as I like chromebooks.
– Neil Butterworth
Nov 16 '18 at 23:36
Hello all, as Kenzel suspected, this was a versioning issue with the g++ compiler. Not sure what my computer was default installing, but a newer version does fix the problem.
– Bronicki
Nov 17 '18 at 16:45
add a comment |
Which version of g++ are you using? This should work with current versions of all major compilers (try for yourself here). In the case of g++, it seems to work starting with version 6.1, which is already pretty old (latest version is 8.2). I guess you must be using a really ancient version…
– Michael Kenzel
Nov 16 '18 at 23:23
I think that you edited this code sample. I was trying it out for myself and it broke until I fixed it. And now your code sample works just fine. What did you do?
– Zan Lynx
Nov 16 '18 at 23:28
Certainly works with GCC 8.1.0. crouron on a chromebook is perhaps not the best C++ development environment - much as I like chromebooks.
– Neil Butterworth
Nov 16 '18 at 23:36
Hello all, as Kenzel suspected, this was a versioning issue with the g++ compiler. Not sure what my computer was default installing, but a newer version does fix the problem.
– Bronicki
Nov 17 '18 at 16:45
Which version of g++ are you using? This should work with current versions of all major compilers (try for yourself here). In the case of g++, it seems to work starting with version 6.1, which is already pretty old (latest version is 8.2). I guess you must be using a really ancient version…
– Michael Kenzel
Nov 16 '18 at 23:23
Which version of g++ are you using? This should work with current versions of all major compilers (try for yourself here). In the case of g++, it seems to work starting with version 6.1, which is already pretty old (latest version is 8.2). I guess you must be using a really ancient version…
– Michael Kenzel
Nov 16 '18 at 23:23
I think that you edited this code sample. I was trying it out for myself and it broke until I fixed it. And now your code sample works just fine. What did you do?
– Zan Lynx
Nov 16 '18 at 23:28
I think that you edited this code sample. I was trying it out for myself and it broke until I fixed it. And now your code sample works just fine. What did you do?
– Zan Lynx
Nov 16 '18 at 23:28
Certainly works with GCC 8.1.0. crouron on a chromebook is perhaps not the best C++ development environment - much as I like chromebooks.
– Neil Butterworth
Nov 16 '18 at 23:36
Certainly works with GCC 8.1.0. crouron on a chromebook is perhaps not the best C++ development environment - much as I like chromebooks.
– Neil Butterworth
Nov 16 '18 at 23:36
Hello all, as Kenzel suspected, this was a versioning issue with the g++ compiler. Not sure what my computer was default installing, but a newer version does fix the problem.
– Bronicki
Nov 17 '18 at 16:45
Hello all, as Kenzel suspected, this was a versioning issue with the g++ compiler. Not sure what my computer was default installing, but a newer version does fix the problem.
– Bronicki
Nov 17 '18 at 16:45
add a comment |
2 Answers
2
active
oldest
votes
Maybe like this?
#include <string>
#include <iostream>
using namespace std::literals;
template<typename... T>
auto add(const T&... args) {
return (args + ...);
}
int main() {
std::cout << add(1,2,3,4) << "n";
std::cout << add("a"s, "b"s, "c"s) << "n";
return 0;
}
answered Nov 16 '18 at 23:22
Zan LynxZan Lynx
41.4k663110
This doesn't really answer why the OP's code doesn't work.
– NathanOliver
Nov 16 '18 at 23:42
@NathanOliver I suspect the asker edited his question because I copied it, and saw the error. And now I don't. So ... ¯_(ツ)_/¯
– Zan Lynx
Nov 17 '18 at 0:50
add a comment |
as Kenzel suspected in the comments, this was a versioning issue with the g++ compiler. Not sure what my computer was installing by default, but going to a linux repository and manually installing a newer version of g++ fixed the issue. Thanks for the help everyone!
answered Nov 17 '18 at 16:51
BronickiBronicki
261
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
Maybe like this?
#include <string>
#include <iostream>
using namespace std::literals;
template<typename... T>
auto add(const T&... args) {
return (args + ...);
}
int main() {
std::cout << add(1,2,3,4) << "n";
std::cout << add("a"s, "b"s, "c"s) << "n";
return 0;
}
answered Nov 16 '18 at 23:22
Zan LynxZan Lynx
41.4k663110
This doesn't really answer why the OP's code doesn't work.
– NathanOliver
Nov 16 '18 at 23:42
@NathanOliver I suspect the asker edited his question because I copied it, and saw the error. And now I don't. So ... ¯_(ツ)_/¯
– Zan Lynx
Nov 17 '18 at 0:50
add a comment |
Maybe like this?
#include <string>
#include <iostream>
using namespace std::literals;
template<typename... T>
auto add(const T&... args) {
return (args + ...);
}
int main() {
std::cout << add(1,2,3,4) << "n";
std::cout << add("a"s, "b"s, "c"s) << "n";
return 0;
}
answered Nov 16 '18 at 23:22
Zan LynxZan Lynx
41.4k663110
This doesn't really answer why the OP's code doesn't work.
– NathanOliver
Nov 16 '18 at 23:42
@NathanOliver I suspect the asker edited his question because I copied it, and saw the error. And now I don't. So ... ¯_(ツ)_/¯
– Zan Lynx
Nov 17 '18 at 0:50
add a comment |
Maybe like this?
#include <string>
#include <iostream>
using namespace std::literals;
template<typename... T>
auto add(const T&... args) {
return (args + ...);
}
int main() {
std::cout << add(1,2,3,4) << "n";
std::cout << add("a"s, "b"s, "c"s) << "n";
return 0;
}
answered Nov 16 '18 at 23:22
Zan LynxZan Lynx
41.4k663110
Maybe like this?
#include <string>
#include <iostream>
using namespace std::literals;
template<typename... T>
auto add(const T&... args) {
return (args + ...);
}
int main() {
std::cout << add(1,2,3,4) << "n";
std::cout << add("a"s, "b"s, "c"s) << "n";
return 0;
}
answered Nov 16 '18 at 23:22
Zan LynxZan Lynx
41.4k663110
answered Nov 16 '18 at 23:22
Zan LynxZan Lynx
41.4k663110
answered Nov 16 '18 at 23:22
Zan LynxZan Lynx
41.4k663110
answered Nov 16 '18 at 23:22
Zan LynxZan Lynx
41.4k663110
41.4k663110
This doesn't really answer why the OP's code doesn't work.
– NathanOliver
Nov 16 '18 at 23:42
@NathanOliver I suspect the asker edited his question because I copied it, and saw the error. And now I don't. So ... ¯_(ツ)_/¯
– Zan Lynx
Nov 17 '18 at 0:50
add a comment |
This doesn't really answer why the OP's code doesn't work.
– NathanOliver
Nov 16 '18 at 23:42
@NathanOliver I suspect the asker edited his question because I copied it, and saw the error. And now I don't. So ... ¯_(ツ)_/¯
– Zan Lynx
Nov 17 '18 at 0:50
This doesn't really answer why the OP's code doesn't work.
– NathanOliver
Nov 16 '18 at 23:42
This doesn't really answer why the OP's code doesn't work.
– NathanOliver
Nov 16 '18 at 23:42
@NathanOliver I suspect the asker edited his question because I copied it, and saw the error. And now I don't. So ... ¯_(ツ)_/¯
– Zan Lynx
Nov 17 '18 at 0:50
@NathanOliver I suspect the asker edited his question because I copied it, and saw the error. And now I don't. So ... ¯_(ツ)_/¯
– Zan Lynx
Nov 17 '18 at 0:50
add a comment |
as Kenzel suspected in the comments, this was a versioning issue with the g++ compiler. Not sure what my computer was installing by default, but going to a linux repository and manually installing a newer version of g++ fixed the issue. Thanks for the help everyone!
answered Nov 17 '18 at 16:51
BronickiBronicki
261
add a comment |
as Kenzel suspected in the comments, this was a versioning issue with the g++ compiler. Not sure what my computer was installing by default, but going to a linux repository and manually installing a newer version of g++ fixed the issue. Thanks for the help everyone!
answered Nov 17 '18 at 16:51
BronickiBronicki
261
add a comment |
as Kenzel suspected in the comments, this was a versioning issue with the g++ compiler. Not sure what my computer was installing by default, but going to a linux repository and manually installing a newer version of g++ fixed the issue. Thanks for the help everyone!
answered Nov 17 '18 at 16:51
BronickiBronicki
261
as Kenzel suspected in the comments, this was a versioning issue with the g++ compiler. Not sure what my computer was installing by default, but going to a linux repository and manually installing a newer version of g++ fixed the issue. Thanks for the help everyone!
answered Nov 17 '18 at 16:51
BronickiBronicki
261
answered Nov 17 '18 at 16:51
BronickiBronicki
261
answered Nov 17 '18 at 16:51
BronickiBronicki
261
answered Nov 17 '18 at 16:51
BronickiBronicki
261
261
add a comment |
add a comment |
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Which version of g++ are you using? This should work with current versions of all major compilers (try for yourself here). In the case of g++, it seems to work starting with version 6.1, which is already pretty old (latest version is 8.2). I guess you must be using a really ancient version…
– Michael Kenzel
Nov 16 '18 at 23:23
I think that you edited this code sample. I was trying it out for myself and it broke until I fixed it. And now your code sample works just fine. What did you do?
– Zan Lynx
Nov 16 '18 at 23:28
Certainly works with GCC 8.1.0. crouron on a chromebook is perhaps not the best C++ development environment - much as I like chromebooks.
– Neil Butterworth
Nov 16 '18 at 23:36
Hello all, as Kenzel suspected, this was a versioning issue with the g++ compiler. Not sure what my computer was default installing, but a newer version does fix the problem.
– Bronicki
Nov 17 '18 at 16:45