As of PHP 5.3 there are two ways to define constants: Either using the const keyword or using the define() function: const FOO = ‘BAR’; define(‘FOO’, ‘BAR’); The fundamental difference between those two ways is that const defines constants at compile time, whereas define defines them at run time. This causes most of const‘s disadvantages. … Read more
There are two aspects to your questions: what are the technical aspects of using const instead of var and what are the human-related aspects of doing so. The technical difference is significant. In compiled languages, a constant will be replaced at compile-time and its use will allow for other optimizations like dead code removal to … Read more
Pros and cons between #defines, consts and (what you have forgot) enums, depending on usage: enums: only possible for integer values properly scoped / identifier clash issues handled nicely, particularly in C++11 enum classes where the enumerations for enum class X are disambiguated by the scope X:: strongly typed, but to a big-enough signed-or-unsigned int … Read more
Since ES2015, JavaScript has a notion of const: const MY_CONSTANT = “some-value”; This will work in pretty much all browsers except IE 8, 9 and 10. Some may also need strict mode enabled. You can use var with conventions like ALL_CAPS to show that certain values should not be modified if you need to support … Read more
That is perfectly acceptable, probably even the standard. (public/private) static final TYPE NAME = VALUE; where TYPE is the type, NAME is the name in all caps with underscores for spaces, and VALUE is the constant value; I highly recommend NOT putting your constants in their own classes or interfaces. As a side note: Variables … Read more
It’s “undefined behavior,” meaning that based on the standard you can’t predict what will happen when you try this. It may do different things depending on the particular machine, compiler, and state of the program. In this case, what will most often happen is that the answer will be “yes.” A variable, const or not, … Read more
No, I believe the allocator requirements say that T can be a “non-const, non-reference object type”. You wouldn’t be able to do much with a vector of constant objects. And a const vector<T> would be almost the same anyway. Many years later this quick-and-dirty answer still seems to be attracting comments and votes. Not always … Read more
From the standard: const char c=”c”; char* pc; const char** pcc = &pc; // not allowed *pcc = &c; *pc=”C”; // would allow to modify a const object
You cannot declare a variable or value as constant in Python. To indicate to programmers that a variable is a constant, one usually writes it in upper case: CONST_NAME = “Name” To raise exceptions when constants are changed, see Constants in Python by Alex Martelli. Note that this is not commonly used in practice. As … Read more
The documentation states: …constant cannot change through re-assignment …constant cannot be re-declared When you’re adding to an array or object you’re not re-assigning or re-declaring the constant, it’s already declared and assigned, you’re just adding to the “list” that the constant points to. So this works fine: const x = {}; x.foo = ‘bar’; console.log(x); … Read more