More closure magic in pseudo-code

gistfile1.txt

// Holly crap! Now we can give the "sum_and_count" function as a parameter.
FUNCTION Calculate_average ( sum_and_count, N1, N2, ..., NN )
  LOCAL VARIABLE sum = 0
  LOCAL VARIABLE count = 0

  FOR_EACH N = N1, N2, ..., NN
      CALL_THE_FOLLOWING_FUNCTION sum_and_count ( N )

  RETURN num / count
END FUNCTION

// --------------------------------------------
// So the user can define its own sum_and_count
// function and pass it to Calculate_average

FUNCTION My_sum_and_count(x)
  sum = sum + x        // Oh, here we are referencing unbound variables,
  count = count + 1    // but this is not a problem yet (inside Calculate_average they 
                       // will be bound)
END LOCAL FUNCTION

// Here we pass "My_sum_and_count" function as a parameter to "Calculate_average"
// function. The interpreter will try to bound all unbound-variables when
// "Calculate_average" uses the "sum_and_count" function.
CALL_THE_FOLLOWING_FUNCTION Calculate_average ( My_sum_and_count, 8, 4, 6, 2, 7 )