CODEWITHSUNDEEP
c
Rüppell's Vulture
Rüppell's Vulture

Reputation: 3663

Does "long int num=24;" and "int num=24L;" do the same thing?

Do both declare & initiate a long integer?

I hope that's not too basic a question for this forum.I want to know if both the above statements achieve the same thing, ie declare a long integer variable num and initialize it to 24.Thanks.

Upvotes: 0

Views: 266

Answers (5)

Kiril Kirov
Kiril Kirov

Reputation: 38183

Not exactly. long int and int are not guaranteed, but supposed to be different sizes. 

long int num = 24;

this is safe, as 24 is an int, that is (implicitly) promoted to long int.

int num = 24L;

this is not that safe IN GENERAL. 24L defines a long int, that is "truncated" to int and if sizeof(int) < sizeof(long int) there COULD be a problem.

Why "IN GENERAL" and "COULD"? Because in this case, both things are the same and safe. But suppose do something like:

int num = xL;

where x is a large number, that can fit in long int but not in int? Then you have an overflow.

Upvotes: 2

user4815162342
user4815162342

Reputation: 155485

One needs to distinguish between the type of the variable and the type of the constant used to initialize the variable.

The first declaration declares a long int variable and initializes it to the value 24L (which is what you get after casting the integer constant 24 to long int). The second declaration declares an int variable and initializes it to the value 24 (which is what you get after casting the long integer constant 24L to int.)

Upvotes: 1

pmg
pmg

Reputation: 108986

Are long int num = 24; and int num = 24L the same?

They're different.

The first "creates" a variable of type long int and implicitly converts the int value 24 to the long int type before assignment. The second "creates" a variable of type int and implicitly converts the long int value 24 to the int type before assignment.

Upvotes: 6

Neil Townsend
Neil Townsend

Reputation: 6084

No. the type of the variable is defined by the type of the variable is defined by the type to its left only:

  • long int num declares the variable num as a long int;
  • int num declares the variable num as an int.

Meanwhile, the right hand side of the equals is also defined independently.

  • 24 is an int;
  • 24L is a long int

The right hand side (in this case the 24 or 24L) may then be forced (ie changed) to fit into the left hand side (in this case the variable num), but never the other way round.

Upvotes: 1

JohnB
JohnB

Reputation: 13743

No, long int declares a long int, and int declares an int variable. The type of the variable never depends on what value it is "initialized" with (more precisely, assigned to). Hence the two declarations are the same if and only if the types long int and int are the same in your environment.

Upvotes: 4

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