Get all subsets from a set

| category: Programming | author: st
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How to extract all combinations (unordered subsets) from a given set in C++?

Let us estimate the count before. Suppose N is the size of a given set, and K is the number of elements in the subset. The count of all combinations (unordered subsets) of size K is

C …

All expressions of 123456789 and signs +/- which value is 100

| category: Programming | author: st

Suppose a string of ordered cyphers 123456789. You can insert signs "+" and "-" between any cyphers to make a correct arithmetical expression. The problem is to find all expressions which sum is 100.

This problem may be interesting for dynamic script languages having the function of a string expression evaluation.

E …

static_cast vs dynamic_cast: undefined behavior

| category: Programming | author: st

Do not use static_cast when you cast from a basic class to a derived one. This may lead to undefined behavior. To handle the polymorphism, a virtual inheritance or a multiple inheritance case always use dynamic_cast instead.

The following short example shows the undefined behavior cases. This works with GCC …

C++11 constructors

| category: Programming | author: st
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According to specification, "...constructor is a special non-static member function of a class that is used to initialize objects of its class type". In addition to basic concepts, C++11 introduces move constructors, initializer list type and brace-enclosed lists of comma-separated initializers.

However the impact of introducing new constructors combining …

SQL Server: temporary tables and constraint names

| category: Programming | author: st

Update. Since the version 2016 SQL Server supports anonymous constraint declaration:

CREATE TABLE #temp_table (
   id1 int NOT NULL,
   id2 int NOT NULL,
   name1 nvarchar(100),
   name2 nvarchar(100),
   PRIMARY KEY (id1, id2),
   UNIQUE (name1, name2)

For earlier versions the solution is below.

Local temporary tables are isolated in the scope …