Question

我试图使用C创建一个简单的货币转换器，但由于某种原因，它一直给我错误＆＃34;错误必须是可修改的左值＆＃34;。我检查了我的代码，但我没有看到任何问题。有什么帮助吗？

 #include <stdio.h>
#include <stdlib.h>
    void main(){
        float jod_usd=1.41, usd_jod=0.71, jod_eur=1.26, eur_jod=0.8, currency;
        char ic;
        int f;
        printf("Enter the number of your conversion option to continue...\n1-  Convert from JOD\n2-  Convert to JOD\n");
        scanf("%d",&f);
        printf("Enter the character of your second currency to continue...\nU - - USD\nE - - EUR\n");
        scanf("%c",&ic);
        printf("Enter your amount:\n");
        scanf("%f",&currency);
        if(f==1&&(ic='U'||ic='u')){
            printf("%.2f JOD  - - %.2f USD\n",currency,(currency*jod_usd));
        }
        if(f==1&&(ic='E'||ic='e')){
            printf("%.2f JOD  - - %.2f EUR\n",currency,(currency*jod_eur));
        }
        if(f==0&&(ic='E'||ic='e')){
            printf("%.2f EUR  - - %.2f JOD\n",currency,(currency*eur_jod));
        }
        if(f==0&&(ic='U'||ic='u')){
            printf("%.2f USD  - - %.2f JOD\n",currency,(currency*usd_jod));
        }
        system("pause");

    }

Answer 1

TL; DR 使用=代替==的错误导致了这一点。

首先，您正在不必要地更改ic的值。

其次，由于运营商的优先权，

  (ic='U'||ic='u')

与

相同

  ((ic='U'||ic) = 'u')

其中，(ic='U'||ic)的结果不是左值。

Answer 2

你确定它不仅仅是一个简单的错误吗？您通常不会分配条件。如果我解决了这个问题，那么你会得到一些程序流程：

Enter the number of your conversion option to continue...
1-  Convert from JOD
2-  Convert to JOD
1
Enter the character of your second currency to continue...
U - - USD
E - - EUR
Enter your amount:

代码

#include <stdio.h>
#include <stdlib.h>
void main(){
    float jod_usd=1.41, usd_jod=0.71, jod_eur=1.26, eur_jod=0.8, currency;
    char ic;
    int f;
    printf("Enter the number of your conversion option to continue...\n1-  Convert from JOD\n2-  Convert to JOD\n");
    scanf("%d",&f);
    printf("Enter the character of your second currency to continue...\nU - - USD\nE - - EUR\n");
    scanf("%c",&ic);
    printf("Enter your amount:\n");
    scanf("%f",&currency);
    if(f==1 && (ic=='U' || ic=='u')){
        printf("%.2f JOD  - - %.2f USD\n",currency,(currency*jod_usd));
    }
    if(f==1&&(ic=='E'||ic=='e')){
        printf("%.2f JOD  - - %.2f EUR\n",currency,(currency*jod_eur));
    }
    if(f==0&&(ic=='E'||ic=='e')){
        printf("%.2f EUR  - - %.2f JOD\n",currency,(currency*eur_jod));
    }
    if(f==0&&(ic=='U'||ic=='u')){
        printf("%.2f USD  - - %.2f JOD\n",currency,(currency*usd_jod));
    }
    system("pause");

}

错误必须是可修改的左值

2 个答案: