C语言 冲突的类型和先前的 x 声明在这里......什么？

Conflicting types and previous declaration of x was here...what?

提问by Bowlslaw

I've been teaching myself C for a few months when I have time, and I have run into a problem I am not sure how to fix.

我已经在有时间的时候自学了几个月 C，但遇到了一个我不知道如何解决的问题。

Specifically, when I try to compile this using gcc, I get:

具体来说，当我尝试使用 gcc 编译它时，我得到：

geometry.c:8: error: conflicting types for ‘trapezoid'
geometry.c:7: note: previous declaration of ‘trapezoid' was here
geometry.c:48: error: conflicting types for ‘trapezoid'
geometry.c:7: note: previous declaration of ‘trapezoid' was here
geometry.c:119: error: conflicting types for ‘trapezoid_area'
geometry.c:59: note: previous implicit declaration of ‘trapezoid_area' was here
geometry.c: In function ‘cone_volume':
geometry.c:128: error: called object ‘3.14100000000000001421085471520200371742248535156e+0' is not a function
geometry.c: In function ‘cylinder_volume':
geometry.c:136: error: called object ‘3.14100000000000001421085471520200371742248535156e+0' is not a function

Now, I think I may need to typecast the functions, but again, I am not sure.

现在，我想我可能需要对函数进行类型转换，但同样，我不确定。

It looks like it wants to read PI, which I had defined as 3.141, as a function. Is there a way I can avoid using the magic number 3.141 (though it's much less of a magic number than others)?

看起来它想要读取 PI，我将其定义为 3.141，作为一个函数。有没有办法避免使用幻数 3.141（尽管它比其他幻数少得多）？

//Geometric formulae
#include <stdio.h>
#include <math.h>

#define PI 3.141

float trapezoid(float b1, float b2, float h);
int trapezoid();
float sphere_volume(float r);
int sphere();
float cone_volume(float r, float h);
int cone();
float pyramid_volume(float b, float h);
int pyramid();
float cylinder_volume(float r, float h);
int cylinder();

int main(void) {
        char selection = 0;

        while(selection != 'q') {
                printf("\t--Geometric Formulas--\n");
                printf("\tSelection an option from the menu: ");
                scanf("%c", & selection);
                switch(selection) {
                        case 1: //Trapezoid area
                                printf("%d", trapezoid());
                                break;
                        case 2: //Sphere volume
                                printf("%d", sphere());
                                break;
                        case 3: //Cone volume
                                printf("%d", cone());
                                break;
                        case 4: //Pyramid volume
                                printf("%d", pyramid());
                                break;
                        case 5: //Cylinder volume
                                printf("%d", cylinder());
                                break;
                        default:
                                break;
                }
        }
}
//      --Shape Menus--
//Trapezoid
int trapezoid() {
        float h = 0, b1 = 0, b2 = 0;
        float traparea;

        printf("\tTrapezoid base 1: ");
        scanf("%3f", &b1);
        printf("\tTrapezoid base 2: ");
        scanf("%3f", &b2);
        printf("\tTrapezoid height: ");
        scanf("%3f", &b2);

        traparea = trapezoid_area(b1, b2, h);

        printf("\tTrapezoid Area: %3f\n", traparea); }

//Sphere
int sphere() {
        float r = 0;
        float spherevol;

        printf("\tSphere radius: ");
        scanf("%f", &r);

        spherevol = sphere_volume(r);

        printf("\tSphere volume: %3f\n", spherevol); }

//Cone
int cone() {
        float r = 0, h = 0;
        float conevol;

        printf("\tCone radius: ");
        scanf("%f", &r);
        printf("\tCone height: ");
        scanf("%f", &h);

        conevol = cone_volume(r, h);

        printf("\tCone volume: %3f\n", conevol); }

//Pyramid
int pyramid() {
        float b = 0, h = 0;
        float pyramidvol;

        printf("\tPyramid base: ");
        scanf("%f", &b);
        printf("\tPyramid height: ");
        scanf("%f", &h);

        pyramidvol = pyramid_volume(b, h);

        printf("\tPyramid volume: %3f\n", pyramidvol); }

//Cylinder
int cylinder() {
        float r = 0, h = 0;
        float cylindervol;

        printf("\tCylinder radius: ");
        scanf("%f", &r);
        printf("\tCylinder height: ");
        scanf("%f", &h);

        cylindervol = cylinder_volume(r, h);

        printf("Cylinder volume: %3f", cylindervol); }

//      --Geometric Formulas--
//Trapezoid Area Computation
float trapezoid_area(float b1, float b2, float h) {
        return ((b1 + b2) * h) / 2; }

//Sphere Volume Computation
float sphere_volume(float r) {
        return ((pow(r,3)) * (4 * PI)) / 3; }

//Cone Volume Computatioin
float cone_volume(float r, float h) {
        return ((PI(pow(r,2)) * h)) / 3; }

//Pyramid Volume Computation
float pyramid_volume(float b, float h) {
        return (b * h) / 3; }

//Cylinder Volume Computation
float cylinder_volume(float r, float h) {
        return (PI(pow(r,2))) * h; }

采纳答案by Brian Vandenberg

Any of them that say there was an 'implicit' definition: this can be solved by pre-declaring it. As an example, you pre-declared float trapezoidand int trapezoid, but you didn't pre-declare trapezoid_area. As others pointed out, you also can't overload in C as you can in C++.

他们中的任何一个说有一个“隐式”定义：这可以通过预先声明来解决。例如，您预先声明了float trapezoid和int trapezoid，但您没有预先声明trapezoid_area。正如其他人指出的那样，您也不能像在 C++ 中那样在 C 中重载。

In a few areas you're trying to do implicit multiplication -- eg, PI(pow(r,2))should be PI * (pow(r,2)).

在一些领域，您尝试进行隐式乘法——例如，PI(pow(r,2))应该是PI * (pow(r,2))。

回答by JaredPar

The errors you're seeing are because you're defining the same function twice with different signatures

您看到的错误是因为您使用不同的签名两次定义相同的函数

float trapezoid(float b1, float b2, float h);
int trapezoid();

Based on your other definitions it looks like the first trapezoidfunctions should be named trapezoid_volume

根据您的其他定义，第一个trapezoid函数似乎应该被命名trapezoid_volume

float trapezoid_volume(float b1, float b2, float h);
int trapezoid();

回答by MSN

Cdoes not support function overloading. C++does.

C不支持函数重载。C++可以。

And since you accidentally declared trapezoid_volumeas trapezoid, you get a compiler error.

由于您不小心声明trapezoid_volume为trapezoid，您会收到编译器错误。

回答by pmg

#define PI 3.141

float trapezoid(float b1, float b2, float h);
int trapezoid();

I think you want

我想你想要

float trapezoid_volume(...);
/*             ^^^^^^^                 */

回答by Heisenbug

you defined twice function trapezoid. C isn't C++. You can't define the same function with different signatures like you do in C++ using overloading features.

你定义了两次函数梯形。C 不是 C++。您不能像在 C++ 中那样使用重载功能定义具有不同签名的相同函数。

回答by Michael Burr

To answer your question about defining PI- pi is usually defined in math.h(as M_PI), but since it's not part fo the actual standard you might need to do some configuration to get it.

要回答您关于定义的问题PI- pi 通常在math.h(as M_PI) 中定义，但由于它不是实际标准的一部分，您可能需要进行一些配置才能获得它。

For example, when using MSVC you need to define _USE_MATH_DEFINESto get it. See

例如，当使用 MSVC 时，您需要定义_USE_MATH_DEFINES以获取它。看

• http://www.gnu.org/s/hello/manual/libc/Mathematical-Constants.html

• http://www.gnu.org/s/hello/manual/libc/Trig-Functions.html#Trig-Functions

  for the GNU C library's information.

• http://www.gnu.org/s/hello/manual/libc/Mathematical-Constants.html

• http://www.gnu.org/s/hello/manual/libc/Trig-Functions.html#Trig-Functions

  GNU C 库的信息。

If your platform doesn't have it, you might want to throw something like the following into a header:

如果您的平台没有它，您可能希望将以下内容放入标题中：

#ifndef
#define M_PI 3.14159265358979323846264338327
#endif