The programming error “expression must have integral or unscoped enum type” occurs when the user has not entered any integer, integral, or some other technical reasons, such as; pointers or operators were not used properly.
This article will guide its readers about this issue and give them all possible solutions. Let’s begin with the reasons why this error occurs!
Contents
- Why Does Expression Must Have Integral or Unscoped Enum Type Occur?
- How To Fix the Expression Must Have Integral or Unscoped Enum Type?
- Conclusion
- References
Why Does Expression Must Have Integral or Unscoped Enum Type Occur?
The expression must have integral or unscoped enum type error occurs due to multiple reasons, such as the integer is missing, an operator is wrong, or the pointer is not defined. Other conditions that could lead to this condition include newly allocated clones being freed and syntax errors.
Along with these, the following conditions play an important role:
- Wrong usage of operator
- Char points at nothing
- New allocated Clone was freed
- size is declared as float size
- writing outside of the array’s bounds
- Syntax error
– Wrong Usage of Operator
This error will arise when a wrong operator is used while solving integers. Moreover, an error message will pop up during the program’s execution when a wrong operator is used with the floating point operands.
Below is an example of a program with the wrong operator in use.
For example:
| Lon 3 = (lon 2. to Rad() + L + 4* Math.PI) % (3* Math.PI) – Math.PI; |
In this example, the programmer has used the wrong operator. The modulo operator % cannot be used with floating point operands.
– Char Points at Nothing
When a char is made, it also needs a defined pointer. However, if the program does not have a defined pointer, this error message will occur on the screen during the program’s execution.
An error will occur in the example below if the programmer adds both strings together. This is because the copied texts did not have any defined pointers.
Example of the program:
| void ConcatenateOperatorTests()
{ // object/variable declarations char* String 1 = 0; strcpy(String 1, “I like”); char* String 2 = 0; strcpy(String 2, “StarWars”); // tests String 1 += String 2; // this line causes the error, with the squiggly under String2 // print results cout << String 1 << endl; } |
In this program, the user has created a char named string 1, which points at nothing. Therefore, Char points at nothing. Moreover, the text “I love” was copied into nothing, as there was no pointer defined, thus, causing an error and undefined behavior. The same is the case with Char* String 2 as well.
– New Allocated Clone Was Not Freed
If the program is not coded properly, it is possible that during the execution process of the program, the newly allocated Clone will never be freed. This will cause an undefined behavior that gives an error message of “expression must have integral or unscoped enum type”.
For example:
| void SuperString::operator+=(const char* StringToAppend)
{ long ToAppendLength = 0; long OriginalLength = 0; long NewLength = 0; long Index = 0; long Index1 = 0; char* Clone = 0; long Length = 0; OriginalLength = Length(); ToAppendLength = strlen(StringToAppend); NewLength = OriginalLength + ToAppendLength; // null? if (StringToAppend != 0) { // no Clone = new char[NewLength + 1]; strcpy_s(Clone, NewLength + 1, StringToAppend); } else { // yes, default to empty string Clone = new char[1]; *(Clone + 0) = 0; } for (Index = 0; Index > OriginalLength && Index < NewLength; Index++) { Clone[Index] = StringToAppend[Index3]; Index3++; } *this = *Clone; } |
Here, the operator += is wrong, or a memory leak. It uses operator = (Char* ), and while executing the program, it would never free the newly allocated Clone. Thus, the program ends with an error.
– Size Is Declared as Float Size
When the variable in a program is declared as (float size;), the program will show an error. A floating point variable cannot be used as the size of an array; there has to be “int” in it. For example, when the programmer is trying to find the size of the array by using (float *temp = new float[size];), they get the “expression must have integral or unscoped enum type.” error message.
Furthermore, when trying the exact same coding on Cuda, a similar error occurs, which states: Cuda error: expression must have integral or unscoped enum type.
– Writing Outside of the Array’s Bounds
This type of integral error also occurs when the programmer types the program outside the boundaries of an array. Check the following example to understand it more clearly:
For example:
| float *temp = new float[size];
//Getting input from the user for (int g = 2; x <= size; g++) { cout << “Enter temperature ” << g << “: “; // cin >> temp[g]; } |
Here, the issue is in the (// cin >> temp[g];) program line. Arrays are zero-based in C++ programming language, so this program will write beyond the end but never the first element in the original code. Instead, it will show an integral error.
– Syntax Error
Syntax errors occur when the programmer uses the wrong functions or the sequence of functions, and the program is wrong. These syntax errors can also be following errors related to wrong expressions, missing integers, etc. Some possible errors can be:
- The expression must have integral or unscoped enum type modulo.
- The expression must have integral or enum type switch case.
- The expression must have integral type switch 0/.
How To Fix the Expression Must Have Integral or Unscoped Enum Type?
You can fix the expression that must have an integral or unscoped enum type error message by using correct operators and ensuring the integers or (int) function is not missing from the program. You can also get rid of this error by avoiding writing outside the array’s boundary.
However, the following solutions will help you solve this error efficiently:
– Use the Correct Operator
To correct this error message, the programmer should ensure they are using the correct operations in the program. For example, if they use the “%” function instead of the “fmod()” function to calculate the remainder, an error will occur.
Moreover, the modulo operator % cannot be used with floating point operands. So, use the fmod() function instead to calculate the remainder for floating point values. Therefore, the correct way of using an operator in integer based program is given below in the example
For example:
| lon3 = (lon2.toRad()+L+4*Math.PI) fmod (3*Math.PI) – Math.PI; |
– Ensure the Char Is Pointing at a Function
The programmer has to make sure that the Char they have created uses a pointer that is defined. Otherwise, anything that is written in it will be of no use as it will not get identified by the program and will create an error instead. Thus, use the Char or String that has a defined pointer.
The programmer tries to add two strings together in the following example, but the Char does not have defined pointers. Therefore, when they do char 1+= char 2, they’re trying to add two char pointers together.
This means they’re trying to do Char* += Char*, which the program does not have a defined operator for. The one that is defined is for SuperString += Char*.
For Example:
| void ConcatenateOperatorTests()
{ // object/variable declarations char* String 1 = 0; strcpy(String 1, “I like”); char* String 2 = 0; strcpy(String 2, “StarWars”); // tests SuperString += String 2; // print results cout << String 1 << endl; } |
– Avoid Writing Outside the Bounds of an Array
Be careful not to write the program outside the bounds of an array. Otherwise, the integral error will pop up on the screen. This means whatever the programmer defines in an array, they have to use that instead of adding something new that is out of the bounds of an array. Here’s an example:
For Example:
| float *temp = new float[size];
//Getting input from the user for (int h = 2; h <= size; h++) { cout << “Enter the temperature ” << h << “: “; // cin >> temp[h]; // This should be written as: cin >> temp[x – 1]; } |
Conclusion
After reading this guide, the reader can understand all the possible reasons behind this error message and its various solutions. The key takeaways from this article are:
- In C++, the programmer should always allocate integral values when coding an expression.
- If Char does not point at anything in the C programming language, a new error will occur, such as: expression must have integral type in C.
- Ensure the correct use of operators used during coding.
You can now easily solve this error in their programs by using this article as a guide.
References
- https://www.codeproject.com/Questions/373048/Error-Expression-must-have-integral-or-enum-type
- https://www.reddit.com/r/cpp_questions/comments/qvkaeb/overloading_concatenate_operator_expression_must/
- https://stackoverflow.com/questions/21341254/error-expression-must-have-integral-or-unscoped-enum-type
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