Identify the Cause
- The error "expected template-name before '<' token" typically occurs when the compiler encounters something unexpected before the '<' symbol, often suggesting a misunderstanding or misuse of C++ templates.
- Review your code to ensure that the class or function template name is correctly defined and matches the intended usage. Misnamed classes or functions can lead to this error.
- Verify that any necessary includes or forward declarations for the template are present. Missing declarations can cause the compiler to misinterpret the template usage.
Check Syntax and Semantics
- Examine your template declarations and definitions for syntax errors. Small mistakes such as missing colons or semicolons can lead to parsing errors.
- Ensure that the typename or class keyword is included where necessary. For example, when declaring a template parameter: ` class MyClass>`. Omitting these keywords can confuse the compiler.
- Check for incorrect usage of namespaces. If the template is defined in a different namespace, ensure that you're using the correct namespace prefix.
Template Declaration Visibility
- Ensure that template definitions are visible to the compiler at the point of instantiation. If the template is defined in a separate file, make sure that file is included where the template is used.
- If working with multiple source files, consider defining the implementation of template classes and functions in header files. This guarantees that the template definitions are available wherever the template is instantiated.
Compiler-Specific Issues
- Check the compatibility of your code with the compiler version you are using. Different compilers or versions can sometimes have stricter requirements or variations in template handling.
- Enable compiler warnings to get more information about the issue, which can often provide hints or details on what might be going wrong.
- If the issue persists, experiment with compiling on another compiler to see if the problem is specific to a certain compiler or flags.
Example Fix
- Suppose you encounter the following error:
template<class T>
class MyClass;
MyClass<int> obj; // Error: expected template-name before '<' token
- Ensure the template is properly defined or included:
template<class T>
class MyClass {
// Implementation details
};
MyClass<int> obj; // Correct usage
- Here, the class `MyClass` is defined with its template parameter before it's used, resolving the error.
