This question already has answers here:
What are the evaluation order guarantees introduced by C++17?
(3 answers)
Order of evaluation of assignment statement in C++
(4 answers)
Closed 4 years ago.
Consider this code:
std::unordered_map<int, std::string> data;
data[5] = foo();
In what order are data[5] and foo() processed? If foo() throws an exception, is the 5 item in data created or not?
If the behaviour depends on version of C++, how do those versions differ?
Related
This question already has answers here:
what will happen when std::move with c style array or not movable object
(2 answers)
Can std::move move a built-in types or c pointer or array
(1 answer)
What is std::move(), and when should it be used?
(9 answers)
Closed 8 months ago.
I want to do something like this:
int data[4] = {1,2,3,4};
int otherData[4];
otherData = std::move(data);
compiler says invalid array assignment, so how can I transfer values from data to otherData
This question already has answers here:
Which operator to overload in order to use my class in an if-statement? [duplicate]
(4 answers)
How do I override the bool operator in a C++ class?
(4 answers)
User Defined Conversions in C++
(4 answers)
Closed 4 years ago.
I am familiar with operator overloading, but a question popped up in my mind.
Is it possible to overload how an object behaves upon evaluating it without any operator? Such as:
Object foo;
if(foo){...}
So i can overload the evaluation with something like:
bool operator evaluation(){
bool isValid=false;
//Some instructions and conditions
return isValid;
}
There's probably little to no reason to do something like this, but I'm a bit new to C++ and I'm just exploring all nooks and crannies of it.
Thank you!
This question already has answers here:
Why are these constructs using pre and post-increment undefined behavior?
(14 answers)
Closed 9 years ago.
#include<stdio.h>
#define max(a) ((++a)*(++a)*(++a))
main(){
int a=5;
printf("%d\n",max(a));
printf("%d",a); }
this should return 6*7*8 but it is returning 7*7*8 why ?
Standard says that you get undefined behavior if you modify variable multiple times between sequence points. That is what you do, so that is what you get.
Note that:
1) You have no promises about order of (++a)*(++a)*(++a) evaluation, apart from operation (multiply) being done after it's arguments calculation (++a).
2) You are explicitly not allowed to modify same variable more than once between sequence points.
This question already has answers here:
Is there a difference between copy initialization and direct initialization?
(9 answers)
Direct Initialization vs Copy Initialization for Primitives
(4 answers)
Closed 9 years ago.
I read the following code in c++:
bool result(false);
is result initialized as false?
but are there any benefits to do it instead of:
bool result = false;
can anyone help?
This question already has answers here:
Closed 10 years ago.
Possible Duplicate:
Is there a difference in C++ between copy initialization and direct initialization?
What's the difference between explicit and implicit assignment in C++
Simple as that. What is the difference between
std::string a("abc");
and
std::string a = "abc";