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What does this colon mean? It is not labeling, it is not ternary operator
What does the explicit keyword mean?What does the C++ standard state the size of int, long type to be?What is the “-->” operator in C++?C++, What does the colon after a constructor mean?What does int argc, char *argv[] mean?What is the meaning of prepended double colon “::”?What are the basic rules and idioms for operator overloading?What does “dereferencing” a pointer mean?What does T&& (double ampersand) mean in C++11?C++11 introduced a standardized memory model. What does it mean? And how is it going to affect C++ programming?
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I don't understand one particular use of a semicolon.
I found it in the book "The C++ programming language" by Bjarne Stroustrup, 4th edition, section 11.4.4, page 297:
void g(double y)
[&] f(y); // return type is void
auto z1 = [=](int x) return x+y; // return type is double
auto z2 = [=,y] if (y) return 1; else return 2; // error : body too complicated
// for retur n type deduction
auto z3 =[y]() return 1 : 2; // (Me: HERE!!!) return type is int
auto z4 = [=,y]()−>int if (y) return 1; else return 2; // OK: explicit return type
All comments from Stroustrup, except the one inside the parentheses.
I have no idea what it could be.
It seems like a conditional ternary operator without the first member (and without the "?"), but in that case I don't understand how it could work without a condition.
c++
asked 1 hour ago
PiockñecPiockñec
363
add a comment |
I don't understand one particular use of a semicolon.
I found it in the book "The C++ programming language" by Bjarne Stroustrup, 4th edition, section 11.4.4, page 297:
void g(double y)
[&] f(y); // return type is void
auto z1 = [=](int x) return x+y; // return type is double
auto z2 = [=,y] if (y) return 1; else return 2; // error : body too complicated
// for retur n type deduction
auto z3 =[y]() return 1 : 2; // (Me: HERE!!!) return type is int
auto z4 = [=,y]()−>int if (y) return 1; else return 2; // OK: explicit return type
All comments from Stroustrup, except the one inside the parentheses.
I have no idea what it could be.
It seems like a conditional ternary operator without the first member (and without the "?"), but in that case I don't understand how it could work without a condition.
c++
asked 1 hour ago
PiockñecPiockñec
363
It's a compile error on my end (gcc and clang). Plus all those lines need semicolons, but still an error.
– Cruz Jean
1 hour ago
add a comment |
I don't understand one particular use of a semicolon.
I found it in the book "The C++ programming language" by Bjarne Stroustrup, 4th edition, section 11.4.4, page 297:
void g(double y)
[&] f(y); // return type is void
auto z1 = [=](int x) return x+y; // return type is double
auto z2 = [=,y] if (y) return 1; else return 2; // error : body too complicated
// for retur n type deduction
auto z3 =[y]() return 1 : 2; // (Me: HERE!!!) return type is int
auto z4 = [=,y]()−>int if (y) return 1; else return 2; // OK: explicit return type
All comments from Stroustrup, except the one inside the parentheses.
I have no idea what it could be.
It seems like a conditional ternary operator without the first member (and without the "?"), but in that case I don't understand how it could work without a condition.
c++
asked 1 hour ago
PiockñecPiockñec
363
I don't understand one particular use of a semicolon.
I found it in the book "The C++ programming language" by Bjarne Stroustrup, 4th edition, section 11.4.4, page 297:
void g(double y)
[&] f(y); // return type is void
auto z1 = [=](int x) return x+y; // return type is double
auto z2 = [=,y] if (y) return 1; else return 2; // error : body too complicated
// for retur n type deduction
auto z3 =[y]() return 1 : 2; // (Me: HERE!!!) return type is int
auto z4 = [=,y]()−>int if (y) return 1; else return 2; // OK: explicit return type
All comments from Stroustrup, except the one inside the parentheses.
I have no idea what it could be.
It seems like a conditional ternary operator without the first member (and without the "?"), but in that case I don't understand how it could work without a condition.
c++
c++
asked 1 hour ago
PiockñecPiockñec
363
asked 1 hour ago
PiockñecPiockñec
363
asked 1 hour ago
PiockñecPiockñec
363
asked 1 hour ago
PiockñecPiockñec
363
asked 1 hour ago
PiockñecPiockñec
363
363
It's a compile error on my end (gcc and clang). Plus all those lines need semicolons, but still an error.
– Cruz Jean
1 hour ago
add a comment |
It's a compile error on my end (gcc and clang). Plus all those lines need semicolons, but still an error.
– Cruz Jean
1 hour ago
It's a compile error on my end (gcc and clang). Plus all those lines need semicolons, but still an error.
– Cruz Jean
1 hour ago
It's a compile error on my end (gcc and clang). Plus all those lines need semicolons, but still an error.
– Cruz Jean
1 hour ago
add a comment |
3 Answers
3
active
oldest
votes
It's a typo. Look at Errata for 2nd and 3rd printings of The C++ Programming Language. The example must be like below:
auto z3 =[y]() return (y) ? 1 : 2;
answered 1 hour ago
S.M.S.M.
6,47241830
add a comment |
Looks to me like a simple typo. Should probably be:
auto z3 =[y]() return y ? 1 : 2;
Note that since the lambda doesn't take any parameters, the parens are optional. You could use this instead, if you preferred:
auto z3 =[y] return y ? 1 : 2;
answered 1 hour ago
Jerry CoffinJerry Coffin
391k52476924
add a comment |
return 1 : 2; is a syntax error, it is not valid code.
A correct statement would be more like return (y) ? 1 : 2; instead.
answered 1 hour ago
Remy LebeauRemy Lebeau
346k19273467
add a comment |
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3 Answers
3
active
oldest
votes
3 Answers
3
active
oldest
votes
active
oldest
votes
active
oldest
votes
It's a typo. Look at Errata for 2nd and 3rd printings of The C++ Programming Language. The example must be like below:
auto z3 =[y]() return (y) ? 1 : 2;
answered 1 hour ago
S.M.S.M.
6,47241830
add a comment |
It's a typo. Look at Errata for 2nd and 3rd printings of The C++ Programming Language. The example must be like below:
auto z3 =[y]() return (y) ? 1 : 2;
answered 1 hour ago
S.M.S.M.
6,47241830
add a comment |
It's a typo. Look at Errata for 2nd and 3rd printings of The C++ Programming Language. The example must be like below:
auto z3 =[y]() return (y) ? 1 : 2;
answered 1 hour ago
S.M.S.M.
6,47241830
It's a typo. Look at Errata for 2nd and 3rd printings of The C++ Programming Language. The example must be like below:
auto z3 =[y]() return (y) ? 1 : 2;
answered 1 hour ago
S.M.S.M.
6,47241830
edited 33 mins ago
answered 1 hour ago
S.M.S.M.
6,47241830
answered 1 hour ago
S.M.S.M.
6,47241830
answered 1 hour ago
S.M.S.M.
6,47241830
6,47241830
add a comment |
add a comment |
Looks to me like a simple typo. Should probably be:
auto z3 =[y]() return y ? 1 : 2;
Note that since the lambda doesn't take any parameters, the parens are optional. You could use this instead, if you preferred:
auto z3 =[y] return y ? 1 : 2;
answered 1 hour ago
Jerry CoffinJerry Coffin
391k52476924
add a comment |
Looks to me like a simple typo. Should probably be:
auto z3 =[y]() return y ? 1 : 2;
Note that since the lambda doesn't take any parameters, the parens are optional. You could use this instead, if you preferred:
auto z3 =[y] return y ? 1 : 2;
answered 1 hour ago
Jerry CoffinJerry Coffin
391k52476924
add a comment |
Looks to me like a simple typo. Should probably be:
auto z3 =[y]() return y ? 1 : 2;
Note that since the lambda doesn't take any parameters, the parens are optional. You could use this instead, if you preferred:
auto z3 =[y] return y ? 1 : 2;
answered 1 hour ago
Jerry CoffinJerry Coffin
391k52476924
Looks to me like a simple typo. Should probably be:
auto z3 =[y]() return y ? 1 : 2;
Note that since the lambda doesn't take any parameters, the parens are optional. You could use this instead, if you preferred:
auto z3 =[y] return y ? 1 : 2;
answered 1 hour ago
Jerry CoffinJerry Coffin
391k52476924
answered 1 hour ago
Jerry CoffinJerry Coffin
391k52476924
answered 1 hour ago
Jerry CoffinJerry Coffin
391k52476924
answered 1 hour ago
Jerry CoffinJerry Coffin
391k52476924
391k52476924
add a comment |
add a comment |
return 1 : 2; is a syntax error, it is not valid code.
A correct statement would be more like return (y) ? 1 : 2; instead.
answered 1 hour ago
Remy LebeauRemy Lebeau
346k19273467
add a comment |
return 1 : 2; is a syntax error, it is not valid code.
A correct statement would be more like return (y) ? 1 : 2; instead.
answered 1 hour ago
Remy LebeauRemy Lebeau
346k19273467
add a comment |
return 1 : 2; is a syntax error, it is not valid code.
A correct statement would be more like return (y) ? 1 : 2; instead.
answered 1 hour ago
Remy LebeauRemy Lebeau
346k19273467
return 1 : 2; is a syntax error, it is not valid code.
A correct statement would be more like return (y) ? 1 : 2; instead.
answered 1 hour ago
Remy LebeauRemy Lebeau
346k19273467
answered 1 hour ago
Remy LebeauRemy Lebeau
346k19273467
answered 1 hour ago
Remy LebeauRemy Lebeau
346k19273467
answered 1 hour ago
Remy LebeauRemy Lebeau
346k19273467
346k19273467
add a comment |
add a comment |
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It's a compile error on my end (gcc and clang). Plus all those lines need semicolons, but still an error.
– Cruz Jean
1 hour ago