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Why do C and C++ allow the expression (int) + 4*5;
Announcing the arrival of Valued Associate #679: Cesar Manara
Planned maintenance scheduled April 23, 2019 at 23:30 UTC (7:30pm US/Eastern)
Data science time! April 2019 and salary with experience
The Ask Question Wizard is Live!Cast int to enum in C#What are the differences between a pointer variable and a reference variable in C++?The Definitive C++ Book Guide and ListDo I cast the result of malloc?Why is “using namespace std” considered bad practice?What is the “-->” operator in C++?C++11 introduced a standardized memory model. What does it mean? And how is it going to affect C++ programming?Why are elementwise additions much faster in separate loops than in a combined loop?Why don't Java's +=, -=, *=, /= compound assignment operators require casting?Why is it faster to process a sorted array than an unsorted array?
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(int) + 4*5;
Why is this possible? (tried with g++ and gcc.)
c++ c casting language-lawyer
edited 35 mins ago
Dai
74.6k15120209
asked 9 hours ago
Ernest BredarErnest Bredar
1135
New contributor
Ernest Bredar is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
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|
show 1 more comment
(int) + 4*5;
Why is this possible? (tried with g++ and gcc.)
c++ c casting language-lawyer
edited 35 mins ago
Dai
74.6k15120209
asked 9 hours ago
Ernest BredarErnest Bredar
1135
New contributor
Ernest Bredar is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
Even this is valid it is not a good idea to do that in a program because yes this is quite disturbing ^^
– bruno
9 hours ago
3
same as(int)-4*5
– P__J__
8 hours ago
Though "(int) (+4.0 * 5.0)" might make more sense, or "(double) (+4 * 5)". But this has me totally puzzled. Why would you write a line of code like this, without assigning the result, and why the heck does the compiler not at least issue a warning?/
– jamesqf
7 hours ago
1
@jamesqf I know that it dosn't make sense, but I want to know why this is possible and for this is sense not needed.
– Ernest Bredar
7 hours ago
4
There is a useful tool calledcppinsightsthat helps to understand how the code looks from the compiler frontend perspective. It also has an online version, you can see what it tells about your example (the same 'parenthesization' as the answers your were given)
– Nikita Kniazev
3 hours ago
|
show 1 more comment
(int) + 4*5;
Why is this possible? (tried with g++ and gcc.)
c++ c casting language-lawyer
edited 35 mins ago
Dai
74.6k15120209
asked 9 hours ago
Ernest BredarErnest Bredar
1135
New contributor
Ernest Bredar is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
(int) + 4*5;
Why is this possible? (tried with g++ and gcc.)
c++ c casting language-lawyer
c++ c casting language-lawyer
edited 35 mins ago
Dai
74.6k15120209
asked 9 hours ago
Ernest BredarErnest Bredar
1135
New contributor
Ernest Bredar is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
edited 35 mins ago
Dai
74.6k15120209
asked 9 hours ago
Ernest BredarErnest Bredar
1135
New contributor
Ernest Bredar is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
edited 35 mins ago
Dai
74.6k15120209
edited 35 mins ago
Dai
74.6k15120209
edited 35 mins ago
Dai
74.6k15120209
74.6k15120209
asked 9 hours ago
Ernest BredarErnest Bredar
1135
New contributor
Ernest Bredar is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
asked 9 hours ago
Ernest BredarErnest Bredar
1135
asked 9 hours ago
Ernest BredarErnest Bredar
1135
1135
New contributor
Ernest Bredar is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
New contributor
Ernest Bredar is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
Ernest Bredar is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
Even this is valid it is not a good idea to do that in a program because yes this is quite disturbing ^^
– bruno
9 hours ago
3
same as(int)-4*5
– P__J__
8 hours ago
Though "(int) (+4.0 * 5.0)" might make more sense, or "(double) (+4 * 5)". But this has me totally puzzled. Why would you write a line of code like this, without assigning the result, and why the heck does the compiler not at least issue a warning?/
– jamesqf
7 hours ago
1
@jamesqf I know that it dosn't make sense, but I want to know why this is possible and for this is sense not needed.
– Ernest Bredar
7 hours ago
4
There is a useful tool calledcppinsightsthat helps to understand how the code looks from the compiler frontend perspective. It also has an online version, you can see what it tells about your example (the same 'parenthesization' as the answers your were given)
– Nikita Kniazev
3 hours ago
|
show 1 more comment
Even this is valid it is not a good idea to do that in a program because yes this is quite disturbing ^^
– bruno
9 hours ago
3
same as(int)-4*5
– P__J__
8 hours ago
Though "(int) (+4.0 * 5.0)" might make more sense, or "(double) (+4 * 5)". But this has me totally puzzled. Why would you write a line of code like this, without assigning the result, and why the heck does the compiler not at least issue a warning?/
– jamesqf
7 hours ago
1
@jamesqf I know that it dosn't make sense, but I want to know why this is possible and for this is sense not needed.
– Ernest Bredar
7 hours ago
4
There is a useful tool calledcppinsightsthat helps to understand how the code looks from the compiler frontend perspective. It also has an online version, you can see what it tells about your example (the same 'parenthesization' as the answers your were given)
– Nikita Kniazev
3 hours ago
Even this is valid it is not a good idea to do that in a program because yes this is quite disturbing ^^
– bruno
9 hours ago
Even this is valid it is not a good idea to do that in a program because yes this is quite disturbing ^^
– bruno
9 hours ago
3
3
same as
(int)-4*5– P__J__
8 hours ago
same as
(int)-4*5– P__J__
8 hours ago
Though "(int) (+4.0 * 5.0)" might make more sense, or "(double) (+4 * 5)". But this has me totally puzzled. Why would you write a line of code like this, without assigning the result, and why the heck does the compiler not at least issue a warning?/
– jamesqf
7 hours ago
Though "(int) (+4.0 * 5.0)" might make more sense, or "(double) (+4 * 5)". But this has me totally puzzled. Why would you write a line of code like this, without assigning the result, and why the heck does the compiler not at least issue a warning?/
– jamesqf
7 hours ago
1
1
@jamesqf I know that it dosn't make sense, but I want to know why this is possible and for this is sense not needed.
– Ernest Bredar
7 hours ago
@jamesqf I know that it dosn't make sense, but I want to know why this is possible and for this is sense not needed.
– Ernest Bredar
7 hours ago
4
4
There is a useful tool called
cppinsights that helps to understand how the code looks from the compiler frontend perspective. It also has an online version, you can see what it tells about your example (the same 'parenthesization' as the answers your were given)– Nikita Kniazev
3 hours ago
There is a useful tool called
cppinsights that helps to understand how the code looks from the compiler frontend perspective. It also has an online version, you can see what it tells about your example (the same 'parenthesization' as the answers your were given)– Nikita Kniazev
3 hours ago
|
show 1 more comment
2 Answers
2
active
oldest
votes
The + here is unary + operator, not the binary addition operator. There's no addition happening here.
Also, the syntax (int) is used for typecasting.
You can re-read that statement as
(int) (+ 4) * 5;
which is parsed as
((int) (+ 4)) * (5);
which says,
- Make the operand
+4 - typecasted to an
int - multiply with operand
5
This is similar to (int) (- 4) * (5);, where the usage of the unary operator is more familiar.
In your case, the unary + and the cast to int - both are redundant.
edited 6 hours ago
Dancrumb
18.2k448103
answered 9 hours ago
Sourav GhoshSourav Ghosh
112k15136194
"Casting", not "typecasting". Typecasting is something that happens to actors.
– Keith Thompson
27 mins ago
(+ 4)is not make the operand+4, it means apply the unary+to operand4, which indeed is a no-op in the OP's case, but could cause integer promotion or array decay in other circumstances. For examplechar c = 0; sizeof +c == sizeof cis probably false andsizeof +"a"is probably not 2.
– chqrlie
1 min ago
add a comment |
This is interpreted as ((int)(+4)) * 5. That is, an expression +4 (a unary plus operator applied to a literal 4), cast to type int with a C-style cast, and the result multiplied by 5.
answered 9 hours ago
Igor TandetnikIgor Tandetnik
33.4k33559
add a comment |
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2 Answers
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active
oldest
votes
2 Answers
2
active
oldest
votes
active
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votes
active
oldest
votes
The + here is unary + operator, not the binary addition operator. There's no addition happening here.
Also, the syntax (int) is used for typecasting.
You can re-read that statement as
(int) (+ 4) * 5;
which is parsed as
((int) (+ 4)) * (5);
which says,
- Make the operand
+4 - typecasted to an
int - multiply with operand
5
This is similar to (int) (- 4) * (5);, where the usage of the unary operator is more familiar.
In your case, the unary + and the cast to int - both are redundant.
edited 6 hours ago
Dancrumb
18.2k448103
answered 9 hours ago
Sourav GhoshSourav Ghosh
112k15136194
"Casting", not "typecasting". Typecasting is something that happens to actors.
– Keith Thompson
27 mins ago
(+ 4)is not make the operand+4, it means apply the unary+to operand4, which indeed is a no-op in the OP's case, but could cause integer promotion or array decay in other circumstances. For examplechar c = 0; sizeof +c == sizeof cis probably false andsizeof +"a"is probably not 2.
– chqrlie
1 min ago
add a comment |
The + here is unary + operator, not the binary addition operator. There's no addition happening here.
Also, the syntax (int) is used for typecasting.
You can re-read that statement as
(int) (+ 4) * 5;
which is parsed as
((int) (+ 4)) * (5);
which says,
- Make the operand
+4 - typecasted to an
int - multiply with operand
5
This is similar to (int) (- 4) * (5);, where the usage of the unary operator is more familiar.
In your case, the unary + and the cast to int - both are redundant.
edited 6 hours ago
Dancrumb
18.2k448103
answered 9 hours ago
Sourav GhoshSourav Ghosh
112k15136194
"Casting", not "typecasting". Typecasting is something that happens to actors.
– Keith Thompson
27 mins ago
(+ 4)is not make the operand+4, it means apply the unary+to operand4, which indeed is a no-op in the OP's case, but could cause integer promotion or array decay in other circumstances. For examplechar c = 0; sizeof +c == sizeof cis probably false andsizeof +"a"is probably not 2.
– chqrlie
1 min ago
add a comment |
The + here is unary + operator, not the binary addition operator. There's no addition happening here.
Also, the syntax (int) is used for typecasting.
You can re-read that statement as
(int) (+ 4) * 5;
which is parsed as
((int) (+ 4)) * (5);
which says,
- Make the operand
+4 - typecasted to an
int - multiply with operand
5
This is similar to (int) (- 4) * (5);, where the usage of the unary operator is more familiar.
In your case, the unary + and the cast to int - both are redundant.
edited 6 hours ago
Dancrumb
18.2k448103
answered 9 hours ago
Sourav GhoshSourav Ghosh
112k15136194
The + here is unary + operator, not the binary addition operator. There's no addition happening here.
Also, the syntax (int) is used for typecasting.
You can re-read that statement as
(int) (+ 4) * 5;
which is parsed as
((int) (+ 4)) * (5);
which says,
- Make the operand
+4 - typecasted to an
int - multiply with operand
5
This is similar to (int) (- 4) * (5);, where the usage of the unary operator is more familiar.
In your case, the unary + and the cast to int - both are redundant.
edited 6 hours ago
Dancrumb
18.2k448103
answered 9 hours ago
Sourav GhoshSourav Ghosh
112k15136194
edited 6 hours ago
Dancrumb
18.2k448103
edited 6 hours ago
Dancrumb
18.2k448103
edited 6 hours ago
Dancrumb
18.2k448103
18.2k448103
answered 9 hours ago
Sourav GhoshSourav Ghosh
112k15136194
answered 9 hours ago
Sourav GhoshSourav Ghosh
112k15136194
answered 9 hours ago
Sourav GhoshSourav Ghosh
112k15136194
112k15136194
"Casting", not "typecasting". Typecasting is something that happens to actors.
– Keith Thompson
27 mins ago
(+ 4)is not make the operand+4, it means apply the unary+to operand4, which indeed is a no-op in the OP's case, but could cause integer promotion or array decay in other circumstances. For examplechar c = 0; sizeof +c == sizeof cis probably false andsizeof +"a"is probably not 2.
– chqrlie
1 min ago
add a comment |
"Casting", not "typecasting". Typecasting is something that happens to actors.
– Keith Thompson
27 mins ago
(+ 4)is not make the operand+4, it means apply the unary+to operand4, which indeed is a no-op in the OP's case, but could cause integer promotion or array decay in other circumstances. For examplechar c = 0; sizeof +c == sizeof cis probably false andsizeof +"a"is probably not 2.
– chqrlie
1 min ago
"Casting", not "typecasting". Typecasting is something that happens to actors.
– Keith Thompson
27 mins ago
"Casting", not "typecasting". Typecasting is something that happens to actors.
– Keith Thompson
27 mins ago
(+ 4) is not make the operand +4, it means apply the unary + to operand 4, which indeed is a no-op in the OP's case, but could cause integer promotion or array decay in other circumstances. For example char c = 0; sizeof +c == sizeof c is probably false and sizeof +"a" is probably not 2.– chqrlie
1 min ago
(+ 4) is not make the operand +4, it means apply the unary + to operand 4, which indeed is a no-op in the OP's case, but could cause integer promotion or array decay in other circumstances. For example char c = 0; sizeof +c == sizeof c is probably false and sizeof +"a" is probably not 2.– chqrlie
1 min ago
add a comment |
This is interpreted as ((int)(+4)) * 5. That is, an expression +4 (a unary plus operator applied to a literal 4), cast to type int with a C-style cast, and the result multiplied by 5.
answered 9 hours ago
Igor TandetnikIgor Tandetnik
33.4k33559
add a comment |
This is interpreted as ((int)(+4)) * 5. That is, an expression +4 (a unary plus operator applied to a literal 4), cast to type int with a C-style cast, and the result multiplied by 5.
answered 9 hours ago
Igor TandetnikIgor Tandetnik
33.4k33559
add a comment |
This is interpreted as ((int)(+4)) * 5. That is, an expression +4 (a unary plus operator applied to a literal 4), cast to type int with a C-style cast, and the result multiplied by 5.
answered 9 hours ago
Igor TandetnikIgor Tandetnik
33.4k33559
This is interpreted as ((int)(+4)) * 5. That is, an expression +4 (a unary plus operator applied to a literal 4), cast to type int with a C-style cast, and the result multiplied by 5.
answered 9 hours ago
Igor TandetnikIgor Tandetnik
33.4k33559
answered 9 hours ago
Igor TandetnikIgor Tandetnik
33.4k33559
answered 9 hours ago
Igor TandetnikIgor Tandetnik
33.4k33559
answered 9 hours ago
Igor TandetnikIgor Tandetnik
33.4k33559
33.4k33559
add a comment |
add a comment |
Ernest Bredar is a new contributor. Be nice, and check out our Code of Conduct.
Ernest Bredar is a new contributor. Be nice, and check out our Code of Conduct.
Ernest Bredar is a new contributor. Be nice, and check out our Code of Conduct.
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Even this is valid it is not a good idea to do that in a program because yes this is quite disturbing ^^
– bruno
9 hours ago
3
same as
(int)-4*5– P__J__
8 hours ago
Though "(int) (+4.0 * 5.0)" might make more sense, or "(double) (+4 * 5)". But this has me totally puzzled. Why would you write a line of code like this, without assigning the result, and why the heck does the compiler not at least issue a warning?/
– jamesqf
7 hours ago
1
@jamesqf I know that it dosn't make sense, but I want to know why this is possible and for this is sense not needed.
– Ernest Bredar
7 hours ago
4
There is a useful tool called
cppinsightsthat helps to understand how the code looks from the compiler frontend perspective. It also has an online version, you can see what it tells about your example (the same 'parenthesization' as the answers your were given)– Nikita Kniazev
3 hours ago