Question

How to use lrint() function to round a floating-point to an integer value using rounding direction fegetround in C

Answer 1

#include <stdio.h>     
#include <math.h> 
#include <fenv.h> 
 
int main(int argc, char **argv)
{   
	fesetround(FE_TONEAREST); 
    printf("rounding to nearest :\n");
    printf("lrint(3.3) = %ld\n", lrint(3.3));
    printf("lrint(3.5) = %ld\n", lrint(3.5));
    printf("lrint(4.5) = %ld\n", lrint(4.5));    
    printf("lrint(4.6) = %ld\n", lrint(4.6));
    printf("lrint(-3.3) = %ld\n", lrint(-3.3));
    printf("lrint(-3.5) = %ld\n", lrint(-3.5));
    printf("lrint(-4.5) = %ld\n", lrint(-4.5));    
    printf("lrint(-4.6) = %ld\n\n", lrint(-4.6));
     
    fesetround(FE_DOWNWARD);
    printf("rounding down: \n");
    printf("lrint(3.3) = %ld\n", lrint(3.3));
    printf("lrint(3.5) = %ld\n", lrint(3.5));
    printf("lrint(4.5) = %ld\n", lrint(4.5));    
    printf("lrint(4.6) = %ld\n", lrint(4.6));
    printf("lrint(-3.3) = %ld\n", lrint(-3.3));
    printf("lrint(-3.5) = %ld\n", lrint(-3.5));
    printf("lrint(-4.5) = %ld\n", lrint(-4.5));    
    printf("lrint(-4.6) = %ld\n\n", lrint(-4.6));
     
    fesetround(FE_UPWARD);
    printf("rounding up: \n");
    printf("lrint(3.3) = %ld\n", lrint(3.3));
    printf("lrint(3.5) = %ld\n", lrint(3.5));
    printf("lrint(4.5) = %ld\n", lrint(4.5));    
    printf("lrint(4.6) = %ld\n", lrint(4.6));
    printf("lrint(-3.3) = %ld\n", lrint(-3.3));
    printf("lrint(-3.5) = %ld\n", lrint(-3.5));
    printf("lrint(-4.5) = %ld\n", lrint(-4.5));    
    printf("lrint(-4.6) = %ld\n\n", lrint(-4.6));
     
    fesetround(FE_TOWARDZERO);
    printf("rounding toward zero: \n");
    printf("lrint(3.3) = %ld\n", lrint(3.3));
    printf("lrint(3.5) = %ld\n", lrint(3.5));
    printf("lrint(4.5) = %ld\n", lrint(4.5));    
    printf("lrint(4.6) = %ld\n", lrint(4.6));
    printf("lrint(-3.3) = %ld\n", lrint(-3.3));
    printf("lrint(-3.5) = %ld\n", lrint(-3.5));
    printf("lrint(-4.5) = %ld\n", lrint(-4.5));    
    printf("lrint(-4.6) = %ld\n\n", lrint(-4.6));
  
    return 0;
}
 
 
/*
run:
   
rounding to nearest :
lrint(3.3) = 3
lrint(3.5) = 4
lrint(4.5) = 4
lrint(4.6) = 5
lrint(-3.3) = -3
lrint(-3.5) = -4
lrint(-4.5) = -4
lrint(-4.6) = -5

rounding down:
lrint(3.3) = 3
lrint(3.5) = 3
lrint(4.5) = 4
lrint(4.6) = 4
lrint(-3.3) = -4
lrint(-3.5) = -4
lrint(-4.5) = -5
lrint(-4.6) = -5

rounding up:
lrint(3.3) = 4
lrint(3.5) = 4
lrint(4.5) = 5
lrint(4.6) = 5
lrint(-3.3) = -3
lrint(-3.5) = -3
lrint(-4.5) = -4
lrint(-4.6) = -4

rounding toward zero:
lrint(3.3) = 3
lrint(3.5) = 3
lrint(4.5) = 4
lrint(4.6) = 4
lrint(-3.3) = -3
lrint(-3.5) = -3
lrint(-4.5) = -4
lrint(-4.6) = -4

*/

 

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