The count method of NSArray returns an NSUInteger, and on the 64-bit OS X platform NSUInteger is defined as unsigned long, and unsigned long is a 64-bit unsigned integer. int is a 32-bit integer. So int is a “smaller” datatype than NSUInteger, therefore the compiler warning. See also NSUInteger in the “Foundation Data Types Reference”: … 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
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
14.8.1/4 in C++98 Implicit conversions (clause 4) will be performed on a function argument to convert it to the type of the corresponding function parameter if the parameter type contains no template-parameters that participate in template argument deduction. Here you would like an instantiation of template <class charT, class traits, class Allocator> basic_ostream<charT, traits>& operator<<(basic_ostream<charT, … Read more
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
That’s because b += 1.0; is equivalent to b = (int) ((b) + (1.0));. The narrowing primitive conversion (JLS 5.1.3) is hidden in the compound assignment operation. JLS 15.26.2 Compound Assignment Operators (JLS Third Edition): A compound assignment expression of the form E1 op= E2 is equivalent to E1 = (T)((E1) op (E2)), where T … 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
If they are related Let’s for a moment assume that B is actually a base of D. Then for the call to check, both versions are viable because Host can be converted to D* and B*. It’s a user defined conversion sequence as described by 13.3.3.1.2 from Host<B, D> to D* and B* respectively. For … Read more
sizeof returns size_t which is unsigned and so -1 is being converted to a very large unsigned number. Using the right warning level would have helped here, clang with the -Wconversion or -Weverything(note this is not for production use) flags warns us: warning: implicit conversion changes signedness: ‘int’ to ‘unsigned long’ [-Wsign-conversion] if (sizeof(int) > … 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