CODEWITHSUNDEEP
c++type-conversionintegerlong-integer
Teasel
Teasel

Reputation: 1340

C++ Is conversion from int to long a promotion?

After numerous research on the web, I couldn't figure out if a conversion from int to long is considered as a promotion or not.

If found the following code on the Microsoft's website here :

long  long_num1, long_num2;
int   int_num;

// int_num promoted to type long prior to assignment.
long_num1 = int_num;

However it's not indicated on the cppreference website.

I understand promotion is a conversion that is value-keeping (doesn't change the value when converting).

Could someone help me figure this out?

Thanks in advance

Upvotes: 3

Views: 883

Answers (2)

IWonderWhatThisAPIDoes
IWonderWhatThisAPIDoes

Reputation: 1048

As far as I know, there is no data loss, as int and long have both the same size of 4 bytes. You can check whether your compiler agrees with this by running the following code:

std::cout << sizeof(int) << ' ' << sizeof(long);

The output should be "4 4". That would mean they are both the same.

EDIT: Sorry; thanks for correcting me. The sizes may vary, use a sizeof whenever referencing them.

Upvotes: 0

KamilCuk
KamilCuk

Reputation: 140970

long  long_num1, long_num2;
int   int_num;

// int_num promoted to type long prior to assignment.
long_num1 = int_num;

The text is incorrect. int_num is not promoted, because it's already an int, so no point applies here.

On assignment, a implicit conversion happens - from source type to destination type. Because long can represent all values of int, the value is not changed and int_num value is converted to a long with the same value.

Upvotes: 2

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