如何解决“模棱两可”的问题？函数调用？
我正在为类开发一个 C++ 程序，我的编译器抱怨“不明确”的函数调用。我怀疑这是因为有几个函数定义了不同的参数。
我如何告诉编译器我想要哪一个？除了特定情况的修复之外，是否有通用规则（例如类型转换）可以解决此类问题？
编辑：
就我而言，我尝试在cout语句内调用abs()，并传入两个double s。
<代码>cout << “金额为：”<< abs(amountOrdered-amountPaid);
Edit2:
我包括这三个标头：
#include <iostream>
#include <fstream>
#include <iomanip>
using namespace std;
Edit3:
我已经完成了没有此代码的程序，但在为了解决这个问题，我重现了这个问题。逐字错误是：
对“abs”的调用不明确。
编译器提供了三个版本的abs，每个版本都采用不同的数据类型作为参数。
I'm working on a C++ program for class, and my compiler is complaining about an "ambiguous" function call. I suspect that this is because there are several functions defined with different parameters.
How can I tell the compiler which one I want? Aside from a case-specific fix, is there a general rule, such as typecasting, which might solve these kinds of problems?
Edit:
In my case, I tried calling abs() inside of a cout statement, passing in two doubles.
cout << "Amount is:" << abs(amountOrdered-amountPaid);
Edit2:
I'm including these three headers:
#include <iostream>
#include <fstream>
#include <iomanip>
using namespace std;
Edit3:
I've finished the program without this code, but in the interest of following through with this question, I've reproduced the problem. The verbatim error is:
Call to 'abs' is ambiguous.
The compiler offers three versions of abs, each taking a different datatype as a parameter.
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发生的情况是，您已经包含了
iostream包含的）以及using namespace std;。此标头在std中声明了两个名为abs()的函数。一个获取并返回long long，另一个返回long。另外，全局命名空间中还有一个来自int）。修复：嗯，采用 double 的
abs()位于What's happened is that you've included
<cstdlib>(indirectly, since it's included byiostream) along withusing namespace std;. This header declares two functions instdwith the nameabs(). One takes and returnslong long, and the other returnslong. Plus, there's the one in the global namespace (that returnsint) that comes from<stdlib.h>.To fix: well, the
abs()that takes double is in<cmath>, and that will actually give you the answer you want!abs函数针对int和long以及long long< 进行了重载/代码>。由于您提供了double作为参数，编译器没有精确的拟合，因此它尝试将double转换为abs的类型> 接受，但它不知道是否应该尝试将其转换为int、long或long long，因此它是不明确的。但您可能确实想要接受
double并返回double的abs。为此，您需要包含当您包含其他不应发生的标头时，似乎
错误：'abs'未在此范围内声明或类似的信息。The
absfunction included by<cstdlib>is overloaded forintandlongandlong long. Since you give adoubleas the argument, the compiler does not have an exact fit, so it tries to convert thedoubleto a type thatabsaccepts, but it does not know if it should try to convert it toint,long, orlong long, hence it's ambiguous.But you probably really want the
absthat takes adoubleand returns adouble. For this you need to include<cmath>. Since thedoubleargument matches exactly, the compiler will not complain.It seems that
<cstdlib>gets included automatically when you include the other headers which should not happen. The compiler should have givenerror: ‘abs’ was not declared in this scopeor something similar.尝试使用< /code> 而其他版本在
fabs。它接受float、double和long double作为参数。abs在abs(int)、abs(long)和abs(long long)定义于Try using
fabsdefined in<cmath>. It takesfloat,doubleandlong doubleas arguments.absis defined both in<cmath>and<cstdlib>. The difference isabs(int),abs(long)andabs(long long)are defined in<cstdlib>while other versions are defined in<cmath>.不知道为什么这没有调用 int 版本的 abs，但您可以尝试将表达式 (amountOrdered - amountPaid) 类型转换为 int ie
Not sure why this isn't calling the int version of abs but you could try type casting the expression (amountOrdered - amountPaid) as int i.e.