Tham khảo tài liệu 'handbooks professional java-c-scrip-sql part 79', công nghệ thông tin, kỹ thuật lập trình phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | boost bind personal_info surname _1 boost bind personal_info surname _2 This is a great technique because it offers an important property simple functionality implemented at the call site. It makes the code easy to understand and maintain. Although it is technically possible to sort using binders based upon complex criteria it is not wise. Adding more logic to the bind expressions quickly loses clarity and succinctness. Although it is sometimes tempting to do more in terms of binding strive to write binders that are as clever as the people who must maintain it but no more so. Functional Composition Part I One problem that s often looking for a solution is to compose a function object out of other functions or function objects. Suppose that you need to test an int to see whether it is greater than 5 and less than or equal to 10. Using regular code you would do something like this if i 5 i 10 Do something When processing elements of a container the preceding code only works if you put it in a separate function. When this is not desirable using a nested bind can express the same thing note that this is typically not possible using bindlst and bind2nd from the Standard Library . If we decompose the problem we find that we need operations for logical and std logical_and greater than std greater and less than or equal to std less_equal . The logical and should look something like this boost bind std logical_and bool _1 _2 Then we need another predicate that answers whether _l is less than or equal to 10. boost bind std greater int _1 5 Then we need another predicate that answers whether _l is less than or equal to 10. boost bind std less_equal int _1 10 Finally we need to logically and those two together like so boost bind std logical_and bool boost bind std greater int _1 5 boost bind std less_equal int _1 10 A nested bind such as this is relatively easy to understand though it has postfix order. Still one can almost read the code literally and determine the intent. Let
