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.
Specifically, when I try to compile this using gcc, I get:
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.
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)?
//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; }
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 trapezoid and 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++.
In a few areas you're trying to do implicit multiplication -- eg, PI(pow(r,2)) should be PI * (pow(r,2)).
The errors you're seeing are because you're defining the same function twice with different signatures
float trapezoid(float b1, float b2, float h);
int trapezoid();
Based on your other definitions it looks like the first trapezoid functions should be named trapezoid_volume
float trapezoid_volume(float b1, float b2, float h);
int trapezoid();
C does not support function overloading. C++ does.
And since you accidentally declared trapezoid_volume as trapezoid, you get a compiler error.
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.
#define PI 3.141
float trapezoid(float b1, float b2, float h);
int trapezoid();
I think you want
float trapezoid_volume(...);
/* ^^^^^^^ */
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.
For example, when using MSVC you need to define _USE_MATH_DEFINES to get it. See
- 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.
If your platform doesn't have it, you might want to throw something like the following into a header:
#ifndef
#define M_PI 3.14159265358979323846264338327
#endif
来源：https://stackoverflow.com/questions/5519029/conflicting-types-and-previous-declaration-of-x-was-here-what