#include "math.h"
#include "stdio.h"

struct cir_area
{
    float l,s;};
    struct cir_area c_area(float a,float b,float c)
    {
        struct cir_area result;
        result.l=(a+b+c)/2;
        reault.s=sqrt(reault.l*(result.l-a)*(result.l-b)*(result.l-c));
        return result;
    }
    void main()
    {
        float a,b,c;
        struct cir_aera triangle;
        printf("输入三角形的3条边长: \n");
        scanf("%f,%f,%f",&a,&b,&c);

        triangle=c_area(a,b,c);
        printf("半周长是: %f\n面积是: %f\n",triangle.l,triangle.s);
    }

哪里错了，运行不了，书上例题，照打的
错误信息------Configuration: 23 - Win32 Debug--------------------
Compiling...
23.cpp
C:\Program Files\Microsoft Visual Studio\23\23.cpp(14) : error C2065: 'reault' : undeclared identifier
C:\Program Files\Microsoft Visual Studio\23\23.cpp(14) : error C2228: left of '.s' must have class/struct/union type
C:\Program Files\Microsoft Visual Studio\23\23.cpp(14) : error C2228: left of '.l' must have class/struct/union type
C:\Program Files\Microsoft Visual Studio\23\23.cpp(20) : error C2079: 'triangle' uses undefined struct 'cir_aera'
C:\Program Files\Microsoft Visual Studio\23\23.cpp(24) : error C2679: binary '=' : no operator defined which takes a right-hand operand of type 'struct cir_area' (or there is no acceptable conversion)
C:\Program Files\Microsoft Visual Studio\23\23.cpp(25) : error C2228: left of '.l' must have class/struct/union type
C:\Program Files\Microsoft Visual Studio\23\23.cpp(25) : error C2228: left of '.s' must have class/struct/union type
执行 cl.exe 时出错.

23.exe - 1 error(s), 0 warning(s)

没啥大错误...   只是好多定义的变量写错了
下面红色字体仔细看看  修改一下

不过你的程序还有一点不足，就是不能判断你输入的三个数是否能构成三角形...

#include "math.h"
#include "stdio.h"

struct cir_area
{
    float l,s;};
    struct cir_area c_area(float a,float b,float c)
    {
        struct cir_area result;
        result.l=(a+b+c)/2;
        reault.s=sqrt(reault.l*(result.l-a)*(result.l-b)*(result.l-c));
        return result;
    }
    void main()
    {
        float a,b,c;
        struct cir_aera triangle;
        printf("输入三角形的3条边长: \n");
        scanf("%f,%f,%f",&a,&b,&c);

        triangle=c_area(a,b,c);
        printf("半周长是: %f\n面积是: %f\n",triangle.l,triangle.s);
    }

还真没看到。。谢谢