C convert floating point to int

问题

I'm using C (not C++).

I need to convert a float number into an int. I do not want to round to the the nearest number, I simply want to eliminate what is after the integer part. Something like

4.9 -> 4.9 -> 4

回答1:

my_var = (int)my_var;

As simple as that. Basically you don't need it if the variable is int.

回答2:

Use in C

int C = var_in_float;

They will convert implicit

Thank you

回答3:

If you want to round it to lower, just cast it.

float my_float = 42.8f;
int my_int;
my_int = (int)my_float;          // => my_int=42

For other purpose, if you want to round it to nearest, you can make a little function or a define like this:

#define FLOAT_TO_INT(x) ((x)>=0?(int)((x)+0.5):(int)((x)-0.5))

float my_float = 42.8f;
int my_int;
my_int = FLOAT_TO_INT(my_float); // => my_int=43

Be careful, ideally you should verify float is between INT_MIN and INT_MAX before casting it.

回答4:

double a = 100.3;
printf("%f %d\n", a, (int)(a* 10.0));

Output Cygwin 100.3 1003
Output MinGW: 100.3 1002

Using (int) to convert double to int seems not to be fail-safe

You can find more about that here: Convert double to int?

来源：https://stackoverflow.com/questions/24723180/c-convert-floating-point-to-int