rustleaf 0.1.0

A simple programming language interpreter written in Rust
Documentation 
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// <p>Each new term in the Fibonacci sequence is generated by adding the previous two terms. By starting with $1$ and $2$, the first $10$ terms will be:
// $$1, 2, 3, 5, 8, 13, 21, 34, 55, 89, \dots$$</p>
// <p>By considering the terms in the Fibonacci sequence whose values do not exceed four million, find the sum of the even-valued terms.</p>

class Fib {
    var a = 1;
    var b = 2;

    fn op_next() {
        var current = self.a;
        var next = self.a + self.b;
        self.a = self.b;
        self.b = next;
        current
    }
}

fn solve_euler_002(limit) {
    Fib()
        : take_while(|x| x < limit)
        : filter(|x| x % 2 == 0)
        : sum()
}

// Test with the example sequence: 1, 2, 3, 5, 8, 13, 21, 34, 55, 89
// Even values under 100: 2, 8, 34 = 44
var test_result = solve_euler_002(100);
print(test_result);
assert(test_result == 44);

// Solve the actual problem
var result = solve_euler_002(4000000);
print("The sum of even-valued Fibonacci terms below 4 million is: ${result}");
assert(result == 4613732);