Dart Programming - Functions

Functions are the building blocks of readable, maintainable, and reusable code. A function is a set of statements to perform a specific task. Functions organize the program into logical blocks of code. Once defined, functions may be called to access code. This makes the code reusable. Moreover, functions make it easy to read and maintain the program’s code.

A function declaration tells the compiler about a function s name, return type, and parameters. A function definition provides the actual body of the function.

Optional Parameters

Optional parameters can be used when arguments need not be compulsorily passed for a function’s execution. A parameter can be marked optional by appending a question mark to its name. The optional parameter should be set as the last argument in a function.

We have three types of optional parameters in Dart −

Recursive Dart Functions

Recursion is a technique for iterating over an operation by having a function call to itself repeatedly until it arrives at a result. Recursion is best appped when you need to call the same function repeatedly with different parameters from within a loop.

Example

void main() { 
   print(factorial(6));
}  
factorial(number) { 
   if (number <= 0) {         
      // termination case 
      return 1; 
   } else { 
      return (number * factorial(number - 1));    
      // function invokes itself 
   } 
}   

720

[return_type]function_name(parameters)=>expression;

void main() { 
   printMsg(); 
   print(test()); 
}  
printMsg()=>
print("hello"); 

int test()=>123;                       
// returning function

hello 123