Question

我有一些代码用if，else if和else语句来评估一些不等式我的问题是：如何将语句的结果（在本例中为单原子，双原子，多原子）分配给字符串变量，以便稍后我可以使用此变量注释图形

/* Determine the type of gas - theoretical gamma for: 
     - monoatomic = 1.66 
     - diatomic = 1.4
     - polyatomic = 1.33 */

if (gamma <=1.36)
    printf("This gas is POLYATOMIC\n");

else if (gamma > 1.36 && gamma <= 1.5)
    printf("This gas is DIATOMIC\n");

else
    printf("This gas is MONOATOMIC\n");

正如您所看到的那样，我只能打印出结果。但是这不能让我以后使用结果。

Answer 1

使用变量存储此信息：

#define POLYATOMIC 3 
#define DIATOMIC 2 
#define MONOATOMIC 1 
#define INVALID 0 

int atomicity = INVALID;
const char* gasTypeName = "ERROR";

if (gamma <=1.36)
{
    atomicity = POLYATOMIC;
    gasTypeName = "Polyatomic";
}
else if (gamma > 1.36 && gamma <= 1.5)
{
    atomicity = DIATOMIC;
    gasTypeName = "Diatomic";
}
else
{
    atomicity = MONOATOMIC;
    gasTypeName = "Monoatomic";
}

printf("The gas is %s", gasTypeName);

Answer 2

您可以使用enum作为gastypes，并为可打印表示使用一组描述字符串。将结果状态存储为整数/枚举具有可以容易地比较它的优点，例如，在switch中使用。相比之下，比较字符串有点麻烦。

以下是使用X-Macros的示例实现：

#include <stdio.h>

#define GASTYPES \
    ENTRY(MONOATOMIC) \
    ENTRY(DIATOMIC) \
    ENTRY(POLYATOMIC)

typedef enum {
#define ENTRY(x) x,
    GASTYPES
#undef ENTRY
} gastype_t;

const char const * gastype_str[] = {
#define ENTRY(x) #x,
    GASTYPES
#undef ENTRY
};

int main() {
    double gamma; 
    gastype_t gastype;
    if(scanf("%lf", &gamma)) {
        if (gamma <= 1.36)
            gastype = POLYATOMIC;
        else if (gamma <= 1.5)
            gastype = DIATOMIC;
        else
            gastype = MONOATOMIC;
        printf("This gas is %s\n", gastype_str[gastype]);
        return 0;
    }
    else {
        printf("Failed to parse input :(\n");
        return -1;
    }
}

因此预处理器在实际编译之前将枚举的定义和描述字符串数组扩展为以下内容：

typedef enum {
    MONOATOMIC,
    DIATOMIC,
    POLYATOMIC,
} gastype_t;

const char const * gastype_str[] = {
    "MONOATOMIC",
    "DIATOMIC",
    "POLYATOMIC",
};

用法示例：

$ gcc test.c && echo "1.4" | ./a.out
This gas is DIATOMIC

将值存储为C中if语句的字符串

2 个答案: