Error invalid operands of types double and double to binary operator

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distance^2 // Change instances of this....
distance * distance // ... to this 

Last edited on

Yup I took that out and gave distance a value as it had not been defined and it worked. Thanks!

Константа с плавающей запятой 1. имеет тип double.

Подобные сообщения об ошибках, как данное

invalid operands to binary % (have ‘double’ and ‘long double’

связаны с тем, как компилятор C осуществляет преобразование операндов с плавающей запятой в выражениях. Например, компилятор может преобразовывать операнды с плавающей запятой к формату, диапазон значений которых и точность превышают соответствующие диапазон значений и точность исходного типа с плавающей запятой. Это делается для того, чтобы в процессе вычислений выражений и их составных подвыражений получать более точные результаты.

Из стандарта C (5.2.4.2.2 Characteristics of floating types <float.h>)

9 Except for assignment and cast (which remove all extra range and
precision), the values yielded by operators with floating operands and
values subject to the usual arithmetic conversions and of floating
constants are evaluated to a format whose range and precision may be
greater than required by the type. The use of evaluation formats is
characterized by the implementation-defined value of
FLT_EVAL_METHOD:24)

-1 indeterminable; 0 evaluate all operations and constants just to the range
and precision of the type;

1 evaluate operations and constants of type float and double to the
range and precision of the double type, evaluate long double
operations and constants to the range and precision of the long double
type;

2 evaluate all operations and constants to the range and precision of
the long double type.

All other negative values for FLT_EVAL_METHOD characterize
implementation-defined behavior.

Если включить заголовок , где имя FLT_EVAL_METHOD определено, то можно получить следующий результат

#include <stdio.h>
#include <float.h>

int main(void) 
{
    printf( "%dn",  FLT_EVAL_METHOD );

    return 0;
}

Вывод на консоль:

2

Как следует из вышеприведенной цитаты из стандарта C это означает, что константы будут преобразованы к типу long double.

Если заголовочный файл <float.h> не включен, тем не менее, видимо, компилятор использует данную опцию по умолчанию для вычисления выражений с плавающей запятой.

The invalid operands to binary expression C++ error might occur when a variable or object is considered a function. Moreover, you might get the same error due to using the wrong types of operands with the operators. If you are still in the same confused state, then read further to find a detailed explanation.

By the end of this post, you’ll surely figure out the erroneous line in your code, understand the reason, and have the perfect solution.

Why Do Invalid Operands To Binary Expression C++ Error Occur?

The above error might be occurring due to the most vexing parse that indicates the interpretation of an object as a function call. Moreover, the invalid operands or the external operands throw the same error. You can read below the complete descriptions of the reasons that have been stated earlier:

– Most Vexing Parse

The most vexing parse tells you that the variable declaration or object creation was considered a function call. Hence, you will get the above error when you use the same variable later in your program as an operand.

You can understand the scenario by imagining that you have declared a variable but accidentally placed a parenthesis in front of it. Next, you’ve coded to store the input inside the same and now, you are trying to print it. Here, you will get the above error because C++ grammar considered the variable declaration as a function call.

The coding block for the above scenario has been attached below:

#include <iostream>
using namespace std;
int main()
{
int age();
cout << “Please enter your age here: “;
cin >> age;
cin.ignore();
cout << “Your age is: “<< age <<“n”;
cin.get();
}

– Using Modulus With Variables of Double Data Type

As shown in the error statement itself, the invalid operands cause the stated error. The most common situation depicting the given reason is when the modulus “%” is used with the operands of double data type. Know that you can use only integers with the modulus.

– Using a Comparison Operator With External Class Objects

You might get the said error while comparing the properties of external class objects.

Here is the code that depicts the above scenario:

#include <iostream>
using namespace std;
class Plant{
public:
int height;
};
int main(){
Plant a, b;
a.height = 20;
b.height = 25;
if(a != b){
// do something
}
}

– Using a Comparison Operator With Operands That Can’t Be Compared

Another reason for the invalid operands error can be comparing the operands that can’t be compared. Here, you can imagine comparing a float variable with the void. It will definitely throw the same error.

You can fix the invalid operands error by implementing one of the solutions shared below as per the erroneous code found in your program:

– Remove the Parenthesis Following the Variable Name

So, if you have confused the C++ compiler regarding the variable and it has interpreted the same as a function, then remove the parenthesis following the variable name. It will solve the issue.

– Cast the Modulus Operands To Int

You can cast the modulus operands to int data type to make the above error go away. Similarly, casting the operands according to the operator requirement will help you every time when you face the same error.

– Round the Function Output and Cast It To Int

If your binary expression that uses the modulus contains the function output as an operand, then it would be a better idea to round the output. Next, you can convert the same into int to make the expression work.

– Overload the Comparison Operator Outside the Class

Pointing towards the error caused while comparing the external class objects’ properties, you can solve the same by overloading the given operator. It will ensure that the operator is already aware of the required class.

Please look at the code shown above that uses the Plant class and then see here to solve the issue:

#include <iostream>
using namespace std;
class Plant{
public:
int height;
};
static bool operator!=(const Plant& obj1, const Plant& obj2) {
return obj1.height != obj2.height;
}
int main(){
Plant a, b;
a.height = 20;
b.height = 25;
if(a != b){
cout << “The heights aren’t the same.” << endl;
}
}

– Fix the Operands To Eliminate Invalid Operands To Binary Expression C++ Error

Double-check the operands that you are comparing and change them accordingly to solve the error.

FAQ

You can find more information in this section.

– What Does the Error “Invalid” Operands To Binary >> (Double and Int) Tells?

The “invalid” operands to binary >> (double and int) error shows up to tell you that you are using the “>>” operator with operands of double data type. Remember that you can use “>>” with the values of integer data type only.

Conclusion

Fixing the stated error in your code isn’t a big deal after learning about the above solutions. Here is the simplified list of the solutions to let you see the fixing processes through the broader side:

• You can fix the above error by removing any syntax errors that confuse the C++ compiler between variables and functions
• Casting and changing the operands as per the operator requirement can help you fix the above error
• Overloading the operators can help you in using external class objects in binary expressions

Certainly, the said error revolves around the invalidity of the operands. You should simply be careful while using the same to avoid the error.