TAILIEUCHUNG - HandBooks Professional Java-C-Scrip-SQL part 89

Tham khảo tài liệu 'handbooks professional java-c-scrip-sql part 89', công nghệ thông tin, kỹ thuật lập trình phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | condition so we move on to the then-part. bind map_type value_type second _1 bind constructor ptr_type bind new_ptr derived There are three bind expressions here the first one we start reading from the left here because the expression involves an assignment extracts the member map_type value_type second which is the smart pointer. This is the value that we assign a new derived to. The second and third expressions are nested so we read them from the inside out. The innermost bind takes care of the default construction of an instance of derived on the heap and to the result we bind a constructor call to ptr_type the smart pointer type which is then assigned using the usual notation for assignment to the very first bind expression. Then we add another expression to this then-part which simply prints out a short message and the element s key. var std cout Created a new derived for bind map_type value_type first _1 . n Finally we add the else-part of the statement which prints out the key of the element and some text. var std cout bind map_type value_type first _1 already has a valid pointer. n When decomposing the expressions it s clear that they re not really that complex although looking at the whole thing can be quite intimidating. It s important to indent and separate the code so that reading becomes intuitive. We can write a similar expression for accomplishing our task in a version that s quite different from this one but is much harder to read although it is slightly more efficient. The thing to note here is that there are often several ways of attacking the problem of writing lambda expressions just as is the case with other programming problems. It makes sense to apply some extra thought before writing because the choices substantially affect the readability of the end result. For comparison here s the other version I mentioned std for_each if_then_else bind map_type value_type second _1 bind static_cast void ptr_type base ptr_type reset base .

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