predicate

2 collections are given with the same number of elements, say List<String> . What are elegant ways in JAVA to apply a functor on each 2 elements of collections with corresponding indexes? Say, one example could be: List<String> = { "APPLE", "PEAR" }; List<String> = { "BANANA", "ORANGE" }; A predicate that joins string together will result in the following List<String> : List<String> = { "APPLEBANANA", "PEARORANGE" }; Akin to the functors found in Apache Commons Collections, I have created binary equivalents in the past. For your situation, a binary transformer type object, which takes to two

I'm basically trying to do this , but I don't know what T will be, so I'm building things up using Reflection and Expression trees. // Input (I don't know about "Book") Type itemType = typeof(Book); // Actual Code // Build up func p => p.AuthorName == "Jon Skeet" ParameterExpression predParam = Expression.Parameter(itemType, "p"); Expression left = Expression.Field(predParam, itemType.GetField("AuthorName")); Expression right = Expression.Constant("Jon Skeet", typeof(string)); Expression equality = Expression.Equal(left, right); Delegate myDelegate = Expression.Lambda(equality, new

I found that both MSVC and GCC compilers allocate at least one byte per each class instance even if the class is a predicate with no member variables (or with just static member variables). The following code illustrates the point. #include <iostream> class A { public: bool operator()(int x) const { return x>0; } }; class B { public: static int v; static bool check(int x) { return x>0; } }; int B::v = 0; void test() { A a; B b; std::cout << "sizeof(A)=" << sizeof(A) << "\n" << "sizeof(a)=" << sizeof(a) << "\n" << "sizeof(B)=" << sizeof(B) << "\n" << "sizeof(b)=" << sizeof(b) << "\n"; } int

You can pass a function pointer, function object (or boost lambda) to std::sort to define a strict weak ordering of the elements of the container you want sorted. However, sometimes (enough that I've hit this several times), you want to be able to chain "primitive" comparisons. A trivial example would be if you were sorting a collection of objects that represent contact data. Sometimes you will want to sort by last name, first name, area code . Other times first name, last name - yet other times age, first name, area code ... etc Now, you can certainly write an additional function object for

I have this : public class Company { public int Id { get; set; } public string Name { get; set; } } public class City { public int Id { get; set; } public string Name { get; set; } public int ZipCode { get; set; } } public class Person { public int Id { get; set; } public string FirstName { get; set; } public string LastName { get; set; } public int? Age { get; set; } public City City { get; set; } public Company Company { get; set; } } I'd like a some case generate the predicate like this : var result = listPerson.Where(x => x.Age == 10).ToList<>(); Or this : var result = listPerson.Where( x

I'm trying to filter a vector so it contains only a specific value. e.g. Make sure the vector only contains elements of the value "abc." Right now, I'm trying to achieve this with remove_copy_if . Is there any way to pass an additional parameter to a predicate when using one of std's algorithms? std::vector<std::string> first, second; first.push_back("abc"); first.push_back("abc"); first.push_back("def"); first.push_back("abd"); first.push_back("cde"); first.push_back("def"); std::remove_copy_if(first.begin(), first.end(), second.begin(), is_invalid); I'm hoping to pass the following function