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C++C ++ 17 - Lazy template functor with caching heavy function computation result

Aug. 22, 2019, 2:42 a.m.

C++17, lambda, auto, functor

Developing the idea of caching the result of calculations of heavy functions , I propose to write a small template class, which will take the function as an argument, namely the lambda function, as the most universal an instrument within which a heavy function will be performed.

In this case, the result of the function will not be calculated at the time of creation of the Functor, but at the time of calling the operator parentheses () . And at the same time, the result will be cached. That will allow not to call a heavy function more than once as part of the execution of a method.

C++C++14 - lambda function with cached return value

Aug. 21, 2019, 4:45 a.m.

lambda, auto, cache, C++14, C++

Suppose we wrote a function that calculates some value or uses a function to calculate this value, while the function_ which calculates the value is quite expensive to calculate and works for a long time. In this case, we call the lambda function several times in some code.

To avoid multiple calls to the heavy function, we can cache the value that the heavy function returns.

C++C++14 - unnamed structure as auto value returned by function

Aug. 21, 2019, 2:56 a.m.

C++, C++14, auto, lambda

Let's look at an interesting construction from the C++14 standard, which allows you to return the structure used in one place of the code, but you need to return an object with named fields.

Such a construction can serve as a replacement for std::tuple. At the same time, we will not need to declare any additional structures that we are not going to transfer anywhere, since we need to get only a set of data that we will somehow use immediately at the place of return and will not transfer further in the same form.

C++C++ - Tutorial 002. Types, Variables and Arithmetic

May 12, 2017, 12:06 p.m.

C++, int, char, double, auto, nullptr

Each variable or expression has its own data type, for example, an declaration

int some_variable;

Indicates that the variable some_variable has an integer type int .

The declaration allows you to enter a variable in the program. This variable will have a certain type of data: integer, floating point, character in the case of basic data types, or custom type (data structure, class). The type of the variable defines the set of operations that can be performed on the variable. The declaration of a variable determines the allocation of the memory area that is required for it. And also the value of this variable, which from the computer's point of view will be a sequence of bits. The declaration of a variable also carries the name by which the programmer will refer to this variable in the program code.

In the above example, we have a variable that has a base integer type, with which arithmetic operations, comparison, assignment, etc. can be performed. Refer to the code in this code by this name by some_variable.

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May 29, 2020, 2:32 p.m.

C ++ - Test 004. Pointers, Arrays and Loops

  • Result:40points,
  • Rating points-8
May 26, 2020, 11:29 a.m.
Artem Sun-Dun-Chan

C ++ - Test 004. Pointers, Arrays and Loops

  • Result:50points,
  • Rating points-4
May 25, 2020, 11:33 a.m.
Mitja Nagibin

C ++ - Test 004. Pointers, Arrays and Loops

  • Result:50points,
  • Rating points-4
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Qt/C++ - Lesson 039. How to paint stroke in QSqlTableModel by value in the column?

QModelIndexList rowIndexes = ui->tableView->selectionModel()->selectedRows(); model->removeRows(rowIndexes.first().row(), rowIndexes.size()); model-&…
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