egg Functions

My first test script for functions in egg was everyone's favourite chestnut: the Fibonacci series.

  int fibonacci(int n) {
    if (n < 2) {
      return n;
    }
    return fibonacci(n - 1) + fibonacci(n - 2);
  }
  print(fibonacci(10));

It does indeed print out "55"!

In egg, functions defined like this are actually special cases of callable objects. The script declares an identifier "fibonacci" which is initialised with an instance of an object that supports the "call" operation: in this case, taking a single integer parameter and returning an integer.

At present, there is no notion of read-only variables in egg, so it's possible to subsequently assign a different function to "fibonacci":

  int fibonacci(int n) {
    if (n < 2) {
      return n;
    }
    return fibonacci(n - 1) + fibonacci(n - 2);
  }
  int zero(int n) {
    return 0;
  }
  fibonacci = zero;
  print(fibonacci(10));

This prints out "0". It's a good demonstration that functions in egg are considered first-class entities, but it might violate the principle of "least surprise" for newcomers.