The unary + operator can be used to convert a value to a number in JavaScript. Underscore appears to be testing that the .length property is a number, otherwise it won’t be equal to itself-converted-to-a-number.
i += 4; means i = i + 4; // increase i by 4. While i =+ 4; is equivalent to i = +4; // assign 4 to i. the unary plus is effectively no-op. (See http://docs.oracle.com/javase/specs/jls/se7/html/jls-15.html#jls-15.15.3 for what a unary + does.)
Unary + can be applied to arithmetic type values, unscoped enumeration values and pointer values because … the C++ standard defines it that way, in C++11 ยง5.3.1/7. In this case the string literal, which is of type array of char const, decays to pointer to char const. It’s always a good idea to look at … Read more
char ch=”a”; std::cout << ch << ‘\n’; std::cout << +ch << ‘\n’; The first insertion writes the character a to cout. The second insertion writes the numeric value of ch to cout. But that’s a bit obscure; it relies on the compiler applying integral promotions for the + operator.
Haskell’s grammar doesn’t allow you to use – like that. Use the subtract function instead: (subtract 3) 2
You can use it as a sort of assertion that an expression has arithmetic type: #define CHECK_ARITHMETIC(x) (+(x)) This will generate a compile-time error if x evaluates to (say) a pointer. That is about the only practical use I can think of.
Use the format specifier %p: printf(“variable A is at address: %p\n”, (void*)&A); The standard requires that the argument is of type void* for %p specifier. Since, printf is a variadic function, there’s no implicit conversion to void * from T * which would happen implicitly for any non-variadic functions in C. Hence, the cast is … Read more
The + operator doesn’t change the sign of the value, and the – operator does change the sign. The outcome of both operators depend on the sign of the original value, neither operator makes the value positive or negative regardless of the original sign. var a = 4; a = -a; // -4 a = … Read more
Yes, 6.2.5c9 is exactly the paragraph that you looked for.
Actually, unary plus does do something – even in C. It performs the usual arithmetic conversions on the operand and returns a new value, which can be an integer of greater width. If the original value was an unsigned integer of lesser width than int, it will be changed to a signed value as well. … Read more