Function pointer & Pointer function Correct Usage

function.c

#include <stdio.h>
#include <assert.h>

typedef double (*PF)(double *dbData, int iSize);

double getMin(double *dbData, int iSize)
{
        double dbMin;
        int i;
        
        assert(iSize > 0);
        dbMin = dbData[0];
        for(i = 1; i < iSize; i++)
                if(dbMin > dbData[i])
                        dbMin = dbData[i];      
        
        return dbMin;   
}

double getMax(double *dbData, int iSize)
{
        double dbMax;
        int i;

        assert(iSize > 0);
        dbMax = dbData[0];
        for(i = 1; i < iSize; i++)
                if(dbMax < dbData[i])
                        dbMax = dbData[i];
        
        return dbMax;   
}


double getAverage(double *dbData, int iSize)
{
        double dbSum = 0;
        int i;

        assert(iSize > 0);
        for(i = 0; i < iSize; i++)
                dbSum += dbData[i];

        return dbSum / iSize;   
}

double unKnown(double *dbData, int iSize)
{
        return 0;       
}

PF getOperation(char c)
{
        switch(c)
        {
                case 'd':       
                        return getMax;
                case 'x':
                        return getMin;
                case 'p':
                        return getAverage;
                default:
                        return unKnown;         
        }       
}

int main(void)
{
        double dbData[] = {3.1415926, 1.4142, -0.5999, -313, 365};
        int iSize = sizeof(dbData) / sizeof(dbData[0]);
        char c;
        
        printf("please input the operation:\n");
        c = getchar();
        printf("result is %1f\n", getOperation(c)(dbData, iSize));      
}