“Need” is a strong word… std::as_const exists because it’s useful, not strictly necessary. Since it’s a function rather than a trait, we can use it to “add const” to actual values rather than to types. More specifically: Suppose I have some variable my_value and I want to treat it as a const, but not copy … Read more
The number itself is always interpreted as a non-negative number. Hexadecimal constants don’t have a sign or any inherent way to express a negative number. The type of the constant is the first one of these which can represent their value: int unsigned int long int unsigned long int long long int unsigned long long … Read more
Generally speaking it is common practice to capitalize your constants. This is a convention which tells other programmers that the value is fixed. The javascript keyword const, though confusing is not a constant in that sense. I think that is where you got confused. A constant is a concept/construct. Not a primitive type within the … Read more
Because constants just aren’t instance members; they’re statically bound to their respective types. In the same way you can’t invoke static methods using instances, you can’t access class constants using instances. If you need to get a constant off an instance without knowing its type first-hand, I suppose you could do it with reflection based … Read more
Yes. That is it. It is often used for enum as well. The only common exception is for logging where you might see private static final Logger log = Logger.getLogger(getClass().getName()); but I prefer LOG I often write this as UPPER_CASE, but I also write TitleCase for classes and camelCase for variables and methods.
You don’t need to use constants in Rails 3.It is better to use the Rails::Application singleton. In your application.rb you can define your constante like: module Yourapp class Application < Rails::Application config.access_request.review = ‘xxx’ end end After in your code you can call Yourapp::Application.config.access_request.review After if you change value in each environment, You just define … Read more
use constant actually makes constant subroutines. To do what you want, you need to explicitly call the sub: use constant X => 1; my %x = ( &X => ‘X’); or use constant X => 1; my %x = ( X() => ‘X’);
There’s no constant for this, but I think it’s more reasonable to hard-code the number in Postgres than it is in Java. In Java, the philosophical goal is for Integer to be an abstract value, so it makes sense that you’d want to behave as if you don’t know what the max value is. In … Read more
This public final static long TESTNG_TEST_TIMEOUT = 300000; is a constant variable, a type of constant expression. This public final static long TESTNG_TEST_TIMEOUT = TimeUnit.MINUTES.toMillis(5); is not. Annotation members expect constant expressions (and a few other things like enums and Class literals).