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// Copyright 2020 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include "base/bind.h"
#include "base/callback.h"
#include "base/logging.h"
#include "base/strings/string_number_conversions.h"
namespace {
struct FibonacciState {
FibonacciState() = default;
int i{0}, j{1};
};
int ComputeNextFibonacciNumber(FibonacciState* state) {
int next = state->i + state->j;
state->i = state->j;
state->j = next;
return state->i;
}
base::RepeatingCallback<int()> MakeFibonacciClosure() {
auto state = std::make_unique<FibonacciState>();
return base::BindRepeating(&ComputeNextFibonacciNumber,
base::Owned(std::move(state)));
}
} // namespace
int main(int argc, char* argv[]) {
if (argc <= 1) {
LOG(INFO) << argv[0] << ": missing operand";
return -1;
}
int n = 0;
if (!base::StringToInt(argv[1], &n) || n < 0) {
LOG(INFO) << argv[0] << ": invalid n '" << argv[1] << "'";
return -1;
}
// |fibonacci_closure1| and |fibonacci_closure2| are independent. Though they
// are bound to the same method, they each have their own |FibonacciState|.
// Running one closure does not affect the other.
base::RepeatingCallback<int()> fibonacci_closure1 = MakeFibonacciClosure();
base::RepeatingCallback<int()> fibonacci_closure2 = MakeFibonacciClosure();
for (int i = 0; i < n; ++i) {
// Run both closures and confirm the values match.
int fibonacci_i = fibonacci_closure1.Run();
int fibonacci_i_backup = fibonacci_closure2.Run();
DCHECK_EQ(fibonacci_i, fibonacci_i_backup);
LOG(INFO) << "F_" << i << " = " << fibonacci_i;
}
return 0;
}
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