Generate lambdas for clarity and performance

Using higher-order functions and lambdas in C++14 can improve both code clarity and performance compared to hand-written loops. The post demonstrates building a generic filtering algorithm, composable lambda-returning functions (like `earns_at_least` and `has_title`), and a `pred_and` combinator. Benchmark results using `perf` on clang++ 3.9 and g++ 6.2 show the higher-order function approach matches or outperforms hand-written loops, partly due to a subtle `std::string` comparison optimization. The key takeaway is that centralizing logic in algorithms and higher-order functions reduces duplication and makes performance fixes easier to apply in one place.