lavish pilot
int a{}, b{21}, sum{a+b}
isnt working how i thought it would.
i use std::cin >>a;
to input a number then i use << sum * 2 <<
in order to mulitply the total of a+b by 2.
instead what happens is that a{} is considered zero and it adds b{21} creating 21 and then it multiplies it by 2 and i just keep getting 42 no matter the number i input for std::cin >>.
i thought once i input a number for a{}, the number i input replaces the zero and then it would add with 21 then multiply by 2.
sudden kayakBOT
lavish pilot
i couldve swore i was making it work yesterday lol
oh. or maybe instead of using a{}; i should just put a; so the computer doesnt think its a zero
let me try that.
nvm doesnt even build when i do that lol
tranquil dome
Yeah that’ll be undefined behavior since ur trying to do addiction on a variable that has no value, or trash value
Can u just move the sum = a + b;
After the cin >> a; ?
vale jacinth
Looks like defined behavior to me.
The issue is that sum doesn't retroactively change its value because a changed.
You changed a with std::cin >> a;, but that has no effect on sum. If you want it to affect sum you have to do it after changing a.
maiden scaffold
a isnt set with a value so it's ub
vale jacinth
a is set to 0.
int a{}; is one of the many ways to initialize an int to 0.
"value initialization"
maiden scaffold
"israel"
tranquil dome
He changed it to a semi colon though in his last change, so it’s ub since it’s a “trash value” (if that’s the right term?)
maiden scaffold
yep
tranquil dome
All’s you gotta do is move the
sum = a + b;
AFTER you do cin >> a;
Because after it then a will have the value you need, to do the addition in sum
maiden scaffold
int a, b = 21, sum;
std::cin >> a;
sum = a + b;
lavish pilot
oh yeah , i didnt mean to write a{}; i just did that because i wrote it there singley. but in my code i had it as a{}, because it was the first
maiden scaffold
let us know how it goes
lavish pilot
You changed `a` with `std::cin >> a;`, but that has no effect on `sum`. If you w...
ah okay
lavish pilot
All’s you gotta do is move the
sum = a + b;
AFTER you do cin >> a;
Because a...
alright, ill try this
okay this seemed to work. i was gonna actually try this eventually but the thing is, i couldve swore last night i was doing it the initial way haha. maybe i was just super tired and i was doing something else.
tranquil dome
Ik it’s confusing at first but basically, the program will step through one line at a time going from top to bottom.
So what u did in ur program was, first you created
int a{}, b{21}, sum{ a + b};
Okay, “a” is equal to zero because you did a{}. So sum is equal to “0 + 21”
Then you did cin >> a;
Okay, that changes the value of “a” ONLY, but not the value of sum.
So then at ur last line u did
sum * 2; Which is just 21 * 2
Since sum never got updated
tranquil dome
okay this seemed to work. i was gonna actually try this eventually but the thing...
U were prob really tired LOL, it happens
lavish pilot
Ik it’s confusing at first but basically, the program will step through one lin...
ah yeah. im aware of this. im learning from Learncpp.com digital textbook and they did go over this.
i just thought its what i did last night haha. i wonder what the hell i was doing last night then. well obviously i was wrong. i learned that the computer doesnt lie HHA.
thank you guys for the help
🙏