The reason you can’t do this is because it is specifically forbidden in the C# language specification: Source: ECMA-334 Section 15.10.4 A class or struct is permitted to declare a conversion from a source type S to a target type T provided all of the following are true: … Neither S nor T is object … Read more
…this is obviously performing a ‘string’ comparison No – if the date/time format matches the supported format, MySQL performs implicit conversion to convert the value to a DATETIME, based on the column it is being compared to. Same thing happens with: WHERE int_column = ‘1’ …where the string value of “1” is converted to an … Read more
The reason why const can only be added one level deep is subtle, and is explained by Question 11.10 in the comp.lang.c FAQ. Briefly, consider this example closely related to yours: const int i; int *p; int const **z = &p; *z = &i; /* Now p points to i */ C avoids this problem … Read more
The standard mentions places where a value may be “contextually converted to bool“. They fall into four main groups: Statements if (t) /* statement */; for (;t;) /* statement */; while (t) /* statement */; do { /* block */ } while (t); Expressions !t t && t2 t || t2 t ? “true” : … Read more
As you’ve defined it, nullchar is an integer constant expression with the value 0. The C++03 standard defines an null pointer constant as: “A null pointer constant is an integral constant expression (5.19) rvalue of integer type that evaluates to zero.” To make a long story short, your nullchar is a null pointer constant, meaning … Read more
Define function template which matches all other types: void function(int); // this will be selected for int only template <class T> void function(T) = delete; // C++11 This is because non-template functions with direct matching are always considered first. Then the function template with direct match are considered – so never function<int> will be used. … Read more
Scala has a restriction on automatic conversions to add a method, which is that it won’t apply more than one conversion in trying to find methods. For example: class A(val n: Int) class B(val m: Int, val n: Int) class C(val m: Int, val n: Int, val o: Int) { def total = m + … Read more
The “%f” format requires an argument of type double. You’re giving it an argument of type int. That’s why the behavior is undefined. The standard does not guarantee that all-bits-zero is a valid representation of 0.0 (though it often is), or of any double value, or that int and double are the same size (remember … Read more
While I don’t want to duplicate my material from Scala In Depth, I think it’s worth noting that type classes / type traits are infinitely more flexible. def foo[T: TypeClass](t: T) = … has the ability to search its local environment for a default type class. However, I can override default behavior at any time … Read more
The reason std::string(0) is valid, is due to 0 being a null pointer constant. So 0 matches the string constructor taking a pointer. Then the code runs afoul of the precondition that one may not pass a null pointer to std::string. Only literal 0 would be interpreted as a null pointer constant, if it was … Read more