C++ does have a power operator—it’s written pow(x, y). Originally, C was designed with system software in mind, and there wasn’t much need for a power operator. (But it has bitwise operators, like & and |, which are absent in a lot of other languages.) There was some discussion of adding one during standardization of … Read more
Not to be confused with the decimal point and dot: var val= 1000..toExponential()
Declare: template<class Func> bool myfunc(char lv, char rv, Func func); Or if you need to link it separately: bool myfunc(char lv, char rv, std::function<bool(bool,bool)> func); Then you can call: myfunc(‘t’, ‘f’, std::logical_or<bool>());
To make the expression a = b; compile you need to either have an operator= in the type of a that takes an element of the type of b, or a type implicitly convertible from b. The first case is ruled out, since operator= must be a member of the class, and since you cannot … Read more
Recommendation: Never use the != operator to compare inequality where one or both arguments are node-sets. By definition the expression: $node-set != $value evaluates to true() exactly when there is at least one node in $node-set such that its string value is not equal to the string value of $value. Using this definition: $empty-nodeset != … Read more
Python Boolean operators return the last value evaluated, not True/False. The docs have a good explanation of this: The expression x and y first evaluates x; if x is false, its value is returned; otherwise, y is evaluated and the resulting value is returned.
Seems that I have finally found a solution: select * from view1 where view1.id = ANY( (select array(select ext_id from aggregate_table order by somedata limit 10) )::integer[] ) order by view1.somedata; After elaborating @Dukeling’s idea: I suspect where id in (1,2,3,4,5,6,7,8,9,10) can be optimised and where id in (select …) can’t, the reason being that … Read more
Set __contains__ makes checks in the following order: ‘Match’ if hash(a) == hash(b) and (a is b or a==b) else ‘No Match’ The relevant C source code is in Objects/setobject.c::set_lookkey() and in Objects/object.c::PyObject_RichCompareBool().
It is a conversion operator that allows the object to be explicitly or implicitly casted to std::string. When such a cast occurs, the operator is invoked and the result of the cast is the result of the invocation. As an example of an implicit cast, suppose you had a function that accepted type std::string or … Read more
When auto is used in user-defined conversion function the type will be deduced via return type deduction, i.e. int for this case (0). This was introduced in C++14. The placeholder auto can be used in conversion-type-id, indicating a deduced return type: struct X { operator int(); // OK operator auto() -> short; // error: trailing … Read more