In the srand manual man srand it says that srand has a unsigned int as its parameter, however when using it without cast the compiler does not complain. Is it possible to go wrong if you do not use cast (unsigned int) ? If yes, what are the possible errors?
An example, comparing the two lines of code below:
srand(time(NULL));
srand((unsigned int)time(NULL));
He is casting implicitly, which has no problems in some cases.
For example:
int x = 3;
double y = 4.5;
x = x + y;
What happens in these cases and the following:
1. Na soma de 'x' com 'y', 'x' e promovido para 'double' e a soma acontece como se ambos fossem desse tipo;
2. O resultado da soma, 7.5, e convertido de volta para 'int', ja que 'x' e do tipo inteiro.
Normally, the compiler does these operations implicitly. You can also do it explicitly, for example:
int x = 65;
printf("%c\n", (char)x);
Now, we interpret x as char to print, then its value of A .
There are, however, cases where these implicit conversions are wrong, especially with pointers.
When you add the header that contains the declaration of the function srand() (the header stdlib.h ) the compiler knows the type of the parameter.
Then it converts the type you used to the required type, if possible. If it is not possible give a message.
#include <stdlib.h>
int main(void) {
srand(42); // ok
srand(4.2); // ok, conversao de 4.2 para 4
srand(srand); // NOT ok! nao é possivel converter pointers para unsigned
}
If you remove #include they are all bad even though the compiler does not complain