check if float number is negative?

isNegative

#include <stdlib.h>
#include <stdio.h>

static int isNegative(float arg){
	char *p = (char*) malloc(20);
	sprintf(p,"%f",arg);
	return p[0] == '-';
}

int main(){
	float f = -3;
	printf("%d",isNegative(f)); 
	return 0;
}