要求是这样的：
create a text-based, menu-driven program that allows the user to choose whether to calculate the circumference of a circle, the area of a circle or the volume of a sphere. The program should then input a radius from the user, perform the appropriate calculation and display the result. Use an array of function pointers in which each pointer represents a function that returns void and receives a double parameter. The corresponding functions should each display messages indicating which calculation was performed, the value of the radius and the result of the calculation.

以下是我写的程序：
#include<stdio.h>
#define P 3.14

void main()
{
    int choice, r;
    float C,A,V;
    printf("Press 1, calculate the circumference of a circle.\n");
    printf("Press 2, calculate the area of a circle.\n");
    printf("Press 3, calculate the volume of a sphere.\n");
    printf("Enter your choice: ");
    scanf ("%d", &choice);
    switch(choice)
    {
    case 1:
        printf("Please enter the radius: ");
        scanf ("%d",&r);
        C = 2*P*r;
        printf("\n The circumference of circle is %.2f",C);
        break;
    case 2:
        printf("Please enter the radius: ");
        scanf ("%d",&r);
        A = P*r*r;
        printf("The area of a circle is %.2f",A);
        break;
    case 3:
        printf("Please enter the radius: ");
        scanf ("%d",&r);
        V = 4/3*P*r*r*r;
        printf("The volume of a sphere is %.2f",V);
        break;
    }
}
我知道不能完全符合要求，但是又没什么思路，哪位大侠给指条明路，多谢啊！！

有啥问题

题目要求用函数指针，楼主的代码不符合题意

没学好英文的路过

刚发现之前贴的代码居然是错的

#include <stdio.h>
#include <math.h>

void show_circumference(double r) {
    printf("Circumference of a circle of radius %lf is %lf\n", r, 2 * M_PI * r);
}

void show_area(double r) {
    printf("Area of a circle of radius %lf is %lf\n", r, M_PI * pow(r, 2));
}

void show_volume(double r) {
    printf("Volume of a sphere of radius %lf is %lf\n", r, 4 * M_PI * pow(r, 3) / 3);
}

int main() {
    int choice = 0;
    double r = 0;
    void (* functions[4])(double) = {NULL, show_circumference, show_area, show_volume};
    printf("Press 1, calculate the circumference of a circle.\n");
    printf("Press 2, calculate the area of a circle.\n");
    printf("Press 3, calculate the volume of a sphere.\n");
    printf("Enter your choice: ");
    while (scanf("%d", &choice) == 0 || choice < 1 || choice > 3) {
        while (getchar() != '\n');
        printf("No kidding! Your choice can be only 1, 2 or 3: ");
    }
    while (getchar() != '\n');
    printf("Enter the radius: ");
    while (!scanf("%lf", &r)) {
        while (getchar() != '\n');
        printf("Please! A decimal number as radius: ");
    }
    functions[choice](r);
    return 0;
}

[ 本帖最后由 voidx 于 2011-6-22 21:57 编辑 ]