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c - 如何将字符串传递给函数，然后检查它是否等于字符串

问题描述

 #include <stdio.h>

typedef struct ComplexNumber_S
{
    float realNumber;
    float img;
} ComplexNumber;

/**
* @brief gets a number
* @return the input number
*/
float GetNumber()
{
    float num;
    while (scanf_s("%f", 9, &num) != 1)
    {
        while (getchar() != '\n');
        printf("Try again: ");
    }
    return num;
}

/**
*  Getting a char from user
*  @return a char
*/
char GettingOperator()
{
    printf("Enter operator: +, -, *, /, any other chars \n");
    char operatorr;
    operatorr = getchar();
    return operatorr;
}

/**
*   Getting a string, asks for real or complex 
*   @return string 
*/
char * GettingType()
{
    char type[8];
    printf("Enter number type: put: real or complex!\n");
    fgets(type, sizeof(type), stdin);
    return type;

}

/**
*   Getting a complex or real number
*   @param - type: real number or complex
*/
ComplexNumber GettingComplexNumber(char *type)
{
    ComplexNumber result;
    result.realNumber = 0.0;
    result.img = 0.0;
    if (type == "real")
    {
        printf("Enter a number\n");
        result.realNumber = GetNumber();
        result.img = 0.0;
    }

    if (type == "complex")
    {
        printf("Enter real number");
        result.realNumber = GetNumber();
        printf("Enter image field");
        result.img = GetNumber();

    }
    return result;
}

/**
*   @param num1 -  a complex number a + bi
*   @param num2 - a commplex number c + di
*
*   @return num1 / num2
*   formula: (ac + bd) / (c^2 + d^2) + i((bc - ad) / (c^2 + d^2))
*/
ComplexNumber Devision(ComplexNumber num1, ComplexNumber num2)
{
    ComplexNumber result;
    float denominator = num2.realNumber * num2.realNumber + num2.img * num2.img;
    result.realNumber = (num1.realNumber * num2.realNumber + num1.img * num2.img) / 
        denominator;
    result.img = (num1.img * num2.realNumber - num1.realNumber * num2.img) /
        denominator;
    return result;

}

/**
*  @param num1 - a + bi
*  @param num2 - c + di
*  @return a complex number 
*  formula:  ac - bd + i(ad + bc)
*/
ComplexNumber Multiplicate(ComplexNumber num1, ComplexNumber num2)
{
    ComplexNumber result;
    result.realNumber = num1.realNumber * num2.realNumber - num1.img * num2.img;
    result.img = num1.realNumber * num2.img + num1.img * num2.realNumber;
    return result;

}

/**
*  
*  @param num1 - a complex number
*  @param num2 - a complex number
*
*  @return num1 - num2 in a complex number
*/
ComplexNumber OperatorMinus(ComplexNumber num1, ComplexNumber num2)
{
    ComplexNumber result;
    result.realNumber = num1.realNumber - num2.realNumber;
    result.img = num1.img - num2.img;
    return result;

}

/**
*  adding two complex numbers.
*  @param num1 - a complex nnumber
*  @param num2 - a complex number
*
*/
ComplexNumber OperatorPlus(ComplexNumber num1, ComplexNumber num2)
{
    ComplexNumber result;
    result.realNumber = num1.realNumber + num2.realNumber;
    result.img = num1.img + num2.img;
    return result;

}

void PrintComplexNumber(ComplexNumber num)
{
    if (num.img > 0.0)
    {
        printf("%.2f + %.2fi", num.realNumber, num.img);
    }
    else
    {
        printf("%.2f  %.2fi", num.realNumber, num.img);
    }
}

/**
*         calculator of complex and real numbers
* @return 0 - when terminates
*/
int main()
{
    char *type;
    type = GettingType();
    ComplexNumber num1 = GettingComplexNumber(type);
    
    char operatorr;
    int ext = 0;
    ComplexNumber num2;
    
    while (ext == 0)
    {
        operatorr = GettingOperator();
        type = GettingType();
        num2 = GettingComplexNumber(type);
        switch (operatorr)
        {
        case '+':
            num1 = OperatorPlus(num1, num2);
            break;
        case '*':
            num1 = Multiplicate(num1, num2);
            break;
        case '/':
            num1 = Devision(num1, num2);
            break;
        case '-':
            num1 = OperatorMinus(num1, num2);
            break;
        default:
            ext = 1;
            break;

        }
    }
    
    PrintComplexNumber(num1);
    return 0;
}

你好！

我试图创建一个复数计算器，但问题是我将初始化char *传递给函数并将其视为null.

我不明白为什么该函数GettingComplexNumber(char *type) 将变量type视为null我之前传递的字符串。

例如，我给出了 input real。当我调试时，我注意到 type = '/0'不是我希望它是“真实的”，所以条件type == "real"是假的

我怎么解决这个问题？

标签： cnull-string

解决方案

在您的GettingType功能上，您声明char type[8];. 这保存type在堆栈中，因此，当函数结束时，内存会丢失。相反，您需要使用 保存type在堆中malloc，即使在函数结束后也会保存数据。考虑这段代码：

char * GettingType()
{
    char *type = (char*)malloc(sizeof(char)*8);
    printf("Enter number type: put: real or complex!\n");
    fgets(type, 8, stdin);
    return type;
}

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