控制可能达到无效功能的结束。频率

Question

我不知道为什么这个程序不会编译。它告诉我有一个问题，但我只是不知道这个代码有什么问题。

我正在哈佛大学在线学习CS50入门课程，而且我在编写这个功能频率时遇到了麻烦。我知道这可以编码得更简单，但我只是没有经验使编程更加顺畅和优雅。问题似乎在功能的最后。我猜我忘了返回一个值，但我不知道发生了什么。

//Calculates frequency (in Hz) of a note

#include <cs50.h>
#include <string.h>
#include <math.h>
#include <stdio.h>

int frequency(string note);

int main(void)
{
string note = get_string();
printf("Piano Note: ");
frequency(note);
return 0;
}

int frequency(string note)
{
char key = note[0];
char accidental;
int octave;

int counter = 0;

while (note != '\0')
{
    counter++;
}

if(counter == 3)
    accidental = note[1];
    octave = note[2];
if(counter == 2)
    octave = note[1];

if (counter == 3)
{
    if (key == 'A')
    {
        if (accidental == '#')
        {
                if(octave == 4)
                {
                    return 466;
                }

                else if(octave < 4)
                {
                    int count = 0, shade = 0;
                    for(int i = 4; i > octave; i--)
                    {
                        count++;
                    }
                    int answer = (440 * pow((double)2, (double)1/12));
                    while(shade != count)
                    {
                        answer /= 2;
                        shade++;
                    }
                    return answer;
                }

                else if(octave > 4)
                {
                    int count = 0, shade = 0;
                    for(int i = 4; i > octave; i--)
                    {
                        count++;
                    }
                    int answer = (440 * pow((double)2, (double)1/12));
                    while(shade != count)
                    {
                        answer *= 2;
                        shade++;
                    }
                    return answer;
                }
        }

        else if (accidental == 'b')
        {
            if(octave == 4)
                {
                    return 415;
                }

                else if(octave < 4)
                {
                    int count = 0, shade = 0;
                    for(int i = 4; i > octave; i--)
                    {
                        count++;
                    }
                    int answer = (440 / pow((double)2, (double)1/12));
                    while(shade != count)
                    {
                        answer /= 2;
                        shade++;
                    }
                    return answer;
                }

                else if(octave > 4)
                {
                    int count = 0, shade = 0;
                    for(int i = 4; i > octave; i--)
                    {
                        count++;
                    }
                    int answer = (440 / pow((double)2, (double)1/12));
                    while(shade != count)
                    {
                        answer *= 2;
                        shade++;
                    }
                    return answer;
                }
        }
    }

    else if (key == 'B')
    {
        if (accidental == '#')
        {
            if(octave == 4)
                {
                    return 523;
                }

                else if(octave < 4)
                {
                    int count = 0, shade = 0;
                    for(int i = 4; i > octave; i--)
                    {
                        count++;
                    }
                    int answer = (440 * pow((double)2, (double)3/12));
                    while(shade != count)
                    {
                        answer /= 2;
                        shade++;
                    }
                    return answer;
                }

                else if(octave > 4)
                {
                    int count = 0, shade = 0;
                    for(int i = 4; i < octave; i++)
                    {
                        count++;
                    }
                    int answer = (440 * pow((double)2, (double)3/12));
                    while(shade != count)
                    {
                        answer *= 2;
                        shade++;
                    }
                    return answer;
        }

        else if (accidental == 'b')
        {
            if(octave == 4)
                {
                    return 466;
                }

                else if(octave < 4)
                {
                    int count = 0, shade = 0;
                    for(int i = 4; i > octave; i--)
                    {
                        count++;
                    }
                    int answer = (440 * pow((double)2, (double)1/12));
                    while(shade != count)
                    {
                        answer /= 2;
                        shade++;
                    }
                    return answer;
                }

                else if(octave > 4)
                {
                    int count = 0, shade = 0;
                    for(int i = 4; i < octave; i++)
                    {
                        count++;
                    }
                    int answer = (440 * pow((double)2, (double)1/12));
                    while(shade != count)
                    {
                        answer *= 2;
                        shade++;
                    }
                    return answer;
        }
    }

    else if (key == 'C')
    {
        if (accidental == '#')
        {
             if(octave == 4)
                {
                    return 277;
                }

                else if(octave > 4)
                {
                    int count = 0, shade = 0;
                    for(int i = 4; i < octave; i++)
                    {
                        count++;
                    }
                    int answer = (440 / pow((double)2, (double)8/12));
                    while(shade != count)
                    {
                        answer *= 2;
                        shade++;
                    }
                    return answer;
                }

                else if (octave < 4)
                {
                    int count = 0, shade = 0;
                    for(int i = 4; i > octave; i--)
                    {
                        count++;
                    }
                    int answer = (440 / pow((double)2, (double)8/12));
                    while(shade != count)
                    {
                        answer /= 2;
                        shade++;
                    }
                    return answer;
        }

        else if (accidental == 'b')
        {
             if(octave == 4)
                {
                    return 247;
                }

                else if(octave > 4)
                {
                    int count = 0, shade = 0;
                    for(int i = 4; i < octave; i++)
                    {
                        count++;
                    }
                    int answer = (440 / pow((double)2, (double)10/12));
                    while(shade != count)
                    {
                        answer *= 2;
                        shade++;
                    }
                    return answer;
                }

                else if (octave < 4)
                {
                    int count = 0, shade = 0;
                    for(int i = 4; i > octave; i--)
                    {
                        count++;
                    }
                    int answer = (440 / pow((double)2, (double)10/12));
                    while(shade != count)
                    {
                        answer /= 2;
                        shade++;
                    }
                    return answer;
        }
    }

    else if (key == 'D')
    {
        if (accidental == '#')
        {
            if(octave == 4)
                {
                    return 311;
                }

                else if(octave > 4)
                {
                    int count = 0, shade = 0;
                    for(int i = 4; i < octave; i++)
                    {
                        count++;
                    }
                    int answer = (440 / pow((double)2, (double)6/12));
                    while(shade != count)
                    {
                        answer *= 2;
                        shade++;
                    }
                    return answer;
                }

                else if(octave < 4)
                {
                    int count = 0, shade = 0;
                    for(int i = 4; i > octave; i--)
                    {
                        count++;
                    }
                    int answer = (440 / pow((double)2, (double)6/12));
                    while(shade != count)
                    {
                        answer /= 2;
                        shade++;
                    }
                    return answer;
        }

        else if (accidental == 'b')
        {
            if(octave == 4)
                {
                    return 277;
                }

                else if(octave > 4)
                {
                    int count = 0, shade = 0;
                    for(int i = 4; i < octave; i++)
                    {
                        count++;
                    }
                    int answer = (440 / pow((double)2, (double)8/12));
                    while(shade != count)
                    {
                        answer *= 2;
                        shade++;
                    }
                    return answer;
                }

                else if(octave < 4)
                {
                    int count = 0, shade = 0;
                    for(int i = 4; i > octave; i--)
                    {
                        count++;
                    }
                    int answer = (440 / pow((double)2, (double)8/12));
                    while(shade != count)
                    {
                        answer /= 2;
                        shade++;
                    }
                    return answer;
        }
    }

    else if (key == 'E')
    {
        if (accidental == '#')
        {
            if(octave == 4)
                {
                    return 349;
                }

                else if(octave > 4)
                {
                    int count = 0, shade = 0;
                    for(int i = 4; i < octave; i++)
                    {
                        count++;
                    }
                    int answer = (440 / pow((double)2, (double)4/12));
                    while(shade != count)
                    {
                        answer *= 2;
                        shade++;
                    }
                    return answer;
                }

                else if(octave < 4)
                {
                    int count = 0, shade = 0;
                    for(int i = 4; i > octave; i--)
                    {
                        count++;
                    }
                    int answer = (440 / pow((double)2, (double)4/12));
                    while(shade != count)
                    {
                        answer /= 2;
                        shade++;
                    }
                    return answer;
        }

        else if (accidental == 'b')
        {
            if(octave == 4)
                {
                    return 311;
                }

                else if(octave > 4)
                {
                    int count = 0, shade = 0;
                    for(int i = 4; i < octave; i++)
                    {
                        count++;
                    }
                    int answer = (440 / pow((double)2, (double)6/12));
                    while(shade != count)
                    {
                        answer *= 2;
                        shade++;
                    }
                    return answer;
                }

                else if(octave < 4)
                {
                    int count = 0, shade = 0;
                    for(int i = 4; i > octave; i--)
                    {
                        count++;
                    }
                    int answer = (440 / pow((double)2, (double)6/12));
                    while(shade != count)
                    {
                        answer /= 2;
                        shade++;
                    }
                    return answer;
        }
    }

    else if (key == 'F')
    {
        if (accidental == '#')
        {
             if(octave == 4)
                {
                    return 370;
                }

                else if(octave > 4)
                {
                    int count = 0, shade = 0;
                    for(int i = 4; i < octave; i++)
                    {
                        count++;
                    }
                    int answer = (440 / pow((double)2, (double)3/12));
                    while(shade != count)
                    {
                        answer *= 2;
                        shade++;
                    }
                    return answer;
                }

                else if(octave < 4)
                {
                    int count = 0, shade = 0;
                    for(int i = 4; i > octave; i--)
                    {
                        count++;
                    }
                    int answer = (440 / pow((double)2, (double)3/12));
                    while(shade != count)
                    {
                        answer /= 2;
                        shade++;
                    }
                    return answer;
        }}

        else if (accidental == 'b')
        {
             if(octave == 4)
                {
                    return 330;
                }

                else if(octave > 4)
                {
                    int count = 0, shade = 0;
                    for(int i = 4; i < octave; i++)
                    {
                        count++;
                    }
                    int answer = (440 / pow((double)2, (double)5/12));
                    while(shade != count)
                    {
                        answer *= 2;
                        shade++;
                    }
                    return answer;
                }

                else if(octave < 4)
                {
                    int count = 0, shade = 0;
                    for(int i = 4; i > octave; i--)
                    {
                        count++;
                    }
                    int answer = (440 / pow((double)2, (double)5/12));
                    while(shade != count)
                    {
                        answer /= 2;
                        shade++;
                    }
                    return answer;
        }
    }

    else if (key == 'G')
    {
        if (accidental == '#')
        {
             if(octave == 4)
                {
                    return 415;
                }

                else if(octave > 4)
                {
                    int count = 0, shade = 0;
                    for(int i = 4; i < octave; i++)
                    {
                        count++;
                    }
                    int answer = (440 / pow((double)2, (double)1/12));
                    while(shade != count)
                    {
                        answer *= 2;
                        shade++;
                    }
                    return answer;
                }

                else if(octave < 4)
                {
                    int count = 0, shade = 0;
                    for(int i = 4; i > octave; i--)
                    {
                        count++;
                    }
                    int answer = (440 / pow((double)2, (double)1/12));
                    while(shade != count)
                    {
                        answer /= 2;
                        shade++;
                    }
                    return answer;
        }

        else if (accidental == 'b')
        {
             if(octave == 4)
                {
                    return 370;
                }

                else if(octave > 4)
                {
                    int count = 0, shade = 0;
                    for(int i = 4; i < octave; i++)
                    {
                        count++;
                    }
                    int answer = (440 / pow((double)2, (double)3/12));
                    while(shade != count)
                    {
                        answer *= 2;
                        shade++;
                    }
                    return answer;
                }

                else if(octave < 4)
                {
                    int count = 0, shade = 0;
                    for(int i = 4; i > octave; i--)
                    {
                        count++;
                    }
                    int answer = (440 / pow((double)2, (double)3/12));
                    while(shade != count)
                    {
                        answer /= 2;
                        shade++;
                    }
                    return answer;
        }
    }
}

    if (counter == 2)
    {
            if(key == 'A')
            {

                if(octave == 4)
                {
                    return 440;
                }

                else if(octave < 4)
                {
                    int count = 0;
                    for(int i = 4; i > octave; i--)
                    {
                        count++;
                    }
                    int divisor = 0, hertz = 440;
                    while(divisor != count)
                    {
                        hertz /= 2;
                        divisor++;
                    }
                    return hertz;
                }

                else if(octave > 4)
                {
                    int count = 0;
                    for(int i = 4; i < octave; i++)
                    {
                        count++;
                    }
                    int divisor = 0, hertz = 440;
                    while(divisor != count)
                    {
                        hertz *= 2;
                        divisor++;
                    }
                    return hertz;
                }
            }

            else if(key == 'B')
            {

                if(octave == 4)
                {
                    return 494;
                }

                else if(octave < 4)
                {
                    int count = 0, shade = 0;
                    for(int i = 4; i > octave; i--)
                    {
                        count++;
                    }
                    int answer = (440 * pow((double)2, (double)2/12));
                    while(shade != count)
                    {
                        answer /= 2;
                        shade++;
                    }
                    return answer;
                }

                else if(octave > 4)
                {
                    int count = 0, shade = 0;
                    for(int i = 4; i < octave; i++)
                    {
                        count++;
                    }
                    int answer = (440 * pow((double)2, (double)2/12));
                    while(shade != count)
                    {
                        answer *= 2;
                        shade++;
                    }
                    return answer;
                }
            }


            else if(key == 'C')
            {
                if(octave == 4)
                {
                    return 262;
                }

                else if(octave > 4)
                {
                    int count = 0, shade = 0;
                    for(int i = 4; i < octave; i++)
                    {
                        count++;
                    }
                    int answer = (440 / pow((double)2, (double)9/12));
                    while(shade != count)
                    {
                        answer *= 2;
                        shade++;
                    }
                    return answer;
                }

                else if (octave < 4)
                {
                    int count = 0, shade = 0;
                    for(int i = 4; i > octave; i--)
                    {
                        count++;
                    }
                    int answer = (440 / pow((double)2, (double)9/12));
                    while(shade != count)
                    {
                        answer /= 2;
                        shade++;
                    }
                    return answer;
                }
            }

            else if(key == 'D')
            {
                if(octave == 4)
                {
                    return 294;
                }

                else if(octave > 4)
                {
                    int count = 0, shade = 0;
                    for(int i = 4; i < octave; i++)
                    {
                        count++;
                    }
                    int answer = (440 / pow((double)2, (double)7/12));
                    while(shade != count)
                    {
                        answer *= 2;
                        shade++;
                    }
                    return answer;
                }

                else if(octave < 4)
                {
                    int count = 0, shade = 0;
                    for(int i = 4; i > octave; i--)
                    {
                        count++;
                    }
                    int answer = (440 / pow((double)2, (double)7/12));
                    while(shade != count)
                    {
                        answer /= 2;
                        shade++;
                    }
                    return answer;
                }
            }

            else if(key == 'E')
            {
                if(octave == 4)
                {
                    return 330;
                }

                else if(octave > 4)
                {
                    int count = 0, shade = 0;
                    for(int i = 4; i < octave; i++)
                    {
                        count++;
                    }
                    int answer = (440 / pow((double)2, (double)5/12));
                    while(shade != count)
                    {
                        answer *= 2;
                        shade++;
                    }
                    return answer;
                }

                else if(octave < 4)
                {
                    int count = 0, shade = 0;
                    for(int i = 4; i > octave; i--)
                    {
                        count++;
                    }
                    int answer = (440 / pow((double)2, (double)5/12));
                    while(shade != count)
                    {
                        answer /= 2;
                        shade++;
                    }
                    return answer;
                }
            }

            else if(key == 'F')
            {
                if(octave == 4)
                {
                    return 349;
                }

                else if(octave > 4)
                {
                    int count = 0, shade = 0;
                    for(int i = 4; i < octave; i++)
                    {
                        count++;
                    }
                    int answer = (440 / pow((double)2, (double)3/12));
                    while(shade != count)
                    {
                        answer *= 2;
                        shade++;
                    }
                    return answer;
                }

                else if(octave < 4)
                {
                    int count = 0, shade = 0;
                    for(int i = 4; i > octave; i--)
                    {
                        count++;
                    }
                    int answer = (440 / pow((double)2, (double)3/12));
                    while(shade != count)
                    {
                        answer /= 2;
                        shade++;
                    }
                    return answer;
                }
            }

            else if(key == 'G')
            {
                if(octave == 4)
                {
                    return 392;
                }

                else if(octave > 4)
                {
                    int count = 0, shade = 0;
                    for(int i = 4; i < octave; i++)
                    {
                        count++;
                    }
                    int answer = (440 / pow((double)2, (double)2/12));
                    while(shade != count)
                    {
                        answer *= 2;
                        shade++;
                    }
                    return answer;
                }

                else if(octave < 4)
                {
                    int count = 0, shade = 0;
                    for(int i = 4; i > octave; i--)
                    {
                        count++;
                    }
                    int answer = (440 / pow((double)2, (double)2/12));
                    while(shade != count)
                    {
                        answer /= 2;
                        shade++;
                    }
                    return answer;
                }

            }
    }
}}}}}}}}}}}}

Answer 1

虽然该代码看起来很糟糕，但是编译错误表明你的函数有一个分支，它将在没有return语句的情况下命中函数的末尾。如果看起来它正常工作，在函数中添加一个默认的返回值，比如int retVal = 0;然后就在你的函数结束之前把行返回retVal;

我没有读完整个示例源代码。你可能有if / elseif / elseif / etc没有else case，它也应该返回默认值，这将通过编译类型错误。

如果您不想返回默认值，请返回错误代码并让调用者检查它以确保它按照您的想法执行操作。

编辑，如果计数器== 1，例如，您的函数将不会返回任何内容。这是编译器试图告诉你的一个例子，可能还有更多。

Answer 2

在fflush(stdout);之后，您需要printf("Piano Note: "); 主功能。 stdout可以是行缓冲的，没有尾随 换行，输出可能不会实际发送到stdout的任何地方 可能就是你的屏幕。

更重要的是，以下循环永远不会终止（假设 那个注意！='\ 0'，

while (note != '\0')
{
    counter++;
}

如果注意！= 0，将进入循环，但循环内没有任何内容 更新注释，因此条件仍然为真，循环将 重新执行。

我没有在任何地方看到'string'的定义。如果这是一个typedef 对于'char *'，这是一个可怕的想法，隐藏指针 会导致混乱。如果它是别的东西，那么很难 说出行为应该是什么。你将它与一个字母进行比较，这意味着 'string'是char的typedef，但这不是很有用， 如果你想要一个字符串。

所以你应该丢失typedef，并且get_string（）应该返回 char *，而不是'string'。我怀疑while循环正在尝试 计算字符串的长度。使用strlen（3）。

我没有算他们，但看起来你可能有太多的近距离支撑 在末尾。当然不会与任何可能的事情对齐 使视觉检查变得容易。