Tips to Solve “error: a function-definition is not allowed here before ‘{‘ token”

C++ is a modern, object-oriented, case-sensitive, and general-purpose programming language. It is a simple language that offers a wide range of projects. Programmers have been using this language for developing operating systems. Even browsers like Chrome and Mozilla Firefox have a core part this is written using C++. When you are working on C++, it is obvious to have errors. Today we discuss the error “error: a function-definition is not allowed here before ‘{‘ token”.

First, we shed light on how you get the error warning, then we go ahead to the solution section. Take a look at how the error occurs

How you land up in the error

When working on a C++ converter for infix to prefix, you get the error. Let’s check out the program code

void main1() 
 {
 
  const int MAX = 50;
 
  class infix
  {
 
  private:
 
  char target[MAX], stack[MAX];
  char *s, *t;
  int top, l;
  public:
  infix( );
  void setexpr ( char *str );
  void push ( char c );
  char pop( );
  void convert( );
  int priority ( char c );
  void show( );
  };
  void infix :: infix( ) //error
  {
  top = -1;
  strcpy ( target, "" );
  strcpy ( stack, "" );
  l = 0;
  }
  void infix :: setexpr ( char *str )//error
  {
  s = str;
  strrev ( s );
  l = strlen ( s );
  * ( target + l ) = '\0';
  t = target + ( l - 1 );
  }
  void infix :: push ( char c )//error
  {
  if ( top == MAX - 1 )
  cout << "\nStack is full\n";
  else
  {
  top++ ;
  stack[top] = c;
  }
  }
 }

After running the code, you end up with this error

"A function-declaration is not allowed here – before '{' token"

Solutions to Fix “error: a function-definition is not allowed here before ‘{‘ token”

With a few solutions, you can get the answer to the error you want to crack.

Solution 1 – Closing Bracket ‘}’

Sometimes a minor issue in the code can lead to serious errors. The most important thing you need to do is to check the program code for any brackets or typing errors. If you miss any closing bracket, you get the error pops up.  You need to make sure there is no mistyping as C++ is a case-sensitive language, you need to work accordingly. This way you can resolve the error.

Solution 2 – Define classes’ function outside the main Function

The error occurs when you define the classes’ function inside the main function. To have your classes’ function inside the main function is not a legal way. To rectify the error, place the class out of the main. The code should be like this

class A
{
public:
 void foo();
};

void A::foo()
{
 <...>
}

int main()
{
 <...>
}

To use the class definition inside the class is not the best practice, though it is also possible to do it. Like this:

int main()
{
 class A
 {
 public:
 void foo()
 {
 <...>
 }
 }
}

Conclusion

To solve the error “error: a function-definition is not allowed here before ‘{‘ token” in an efficient way, we shed light on the best solutions that are simple to implement.

I hope you find it helpful!

Don’t hesitate to drop a message below if you need assistance! We would love to help you!

Reference Source: https://www.configrouter.com/error-a-function-definition-is-not-allowed-here-before-token-closed-20990/

https://www.appsloveworld.com/cplus/100/109/is-a-function-definition-not-allowed-here-before-a-token