constants

问题 I have problem running a Java RCP application via Java Webstart. This works for others in the team, but not for me. (don't you just love those sort of problems) I believe the problem is that it is downloading the 32 bit version of the application, not the 64 bit. When I look at the webstart .log file on my machine I can see the following. !SESSION 2012-07-06 16:24:37.672 ----------------------------------------------- eclipse.buildId=unknown java.version=1.6.0_32 java.vendor=Sun Microsystems

问题 Let's say I have a constants class containing 200+ static fields : class AnimalConstants { static final int AARDVARK = 1; static final int ANTELOPE = 2; static final int BEAR = 3; ... ... static final int ZEBRA = 200; } Can anyone explain if there are any negative impact on performance and memory from using such classes. Would it be better or worse if the class is changed to an interface (e.g. SwingConstants) and being implemented by some classes? Would it be better or worse if I implement

问题 I'm assigning an array constant like this: NUMS = *(2..9) Rubocop says C: Freeze mutable objects assigned to constants. NUMS = *(2..9) ^^^^^ So I try NUMS = *(2..9).freeze Rubocop says C: Freeze mutable objects assigned to constants. NUMS = *(2..9).freeze ^^^^^^^^^^^^ Tried NUMS = (*(2..9)).freeze Rubocop says E: unexpected token tRPAREN (Using Ruby 2.0 parser; configure using TargetRubyVersion parameter, under AllCops) NUMS = (*(2..9)).freeze ^ Tried NUMS = [1, 2, 3, 4, 5, 6, 7, 8, 9].freeze

问题 I'm trying to instantiate an array in Rust. Here's one way I could do it at runtime: let mut t = [0_u32; 65]; for i in 0..t.len() { t[i] = ((i as f64).sin().abs() * 2.0_f64.powf(32.0)).floor() as u32; } However, since I'm never going to change the values of this array and I'm going to use the values a lot, I thought this might be a good opportunity to explore the cool stuff going on with the const compile-time evaluation work being done in Rust. I could make it compute the array at compile

问题 I have a set of constants declared in Perl: use constant C1 => 111; use constant C2 => 222; .. use constant C9 => 999; my $which_constant = "C2"; How do I construct a Perl expression which, based on $which_constant , derives the value of a constant named with the value of this variable - e.g. "222". Please note that I can not change any of the conditions above - they are a simplification of a real scenario: I have a module (which I have no control over) from which these constants are imported

问题 I was just reading the secret pseudo-constants, namely the Space fleet constant <=><=><=> Space fleet 0 This seems to be because the outer <=> is doing something I don't understand. My question is why does my $foo = <=>; Set $foo to = ? Other non-alphanumerics seem to work too, my $foo = <=>; my $foo = <->; my $foo = </>; But, alphanumerics don't... my $foo = <a>; Moreover, the perlsecret pod is confusing to me, Even though it looks like a sequence of three spaceship operators, only the

问题 I was just reading the secret pseudo-constants, namely the Space fleet constant <=><=><=> Space fleet 0 This seems to be because the outer <=> is doing something I don't understand. My question is why does my $foo = <=>; Set $foo to = ? Other non-alphanumerics seem to work too, my $foo = <=>; my $foo = <->; my $foo = </>; But, alphanumerics don't... my $foo = <a>; Moreover, the perlsecret pod is confusing to me, Even though it looks like a sequence of three spaceship operators, only the

问题 In A Tour of C++ by Bjarne Stroustrup, some advice is listed at the end of each chapter. At the end of the first chapter one of them reads: Avoid ‘‘magic constants;’’ use symbolic constants; What are magic and symbolic constants? 回答1: somethingElse = something * 1440; // a magic constant somethingElse = something * TWIPS_PER_INCH; // a symbolic one The first is an example of the magic constant, it conveys no other information other than its value. The latter is far more useful since the

问题 Can anyone tell me why this doesn't work? It's just a crude example of what I'm trying to do somewhere else. $stuff = array( 'key' => __DIR__ . 'value' ); However, this produces an error: PHP Parse error: syntax error, unexpected '.', expecting ')' in /var/www/.../testing.php on line 6 Also, this works: $stuff = array( 'key' => "{__DIR__} value" ); 回答1: The first piece of code does not work because it's not a constant expression, as you are trying to concatenate two strings. Initial class

问题 In Modelica, one could define a protected final constant Boolean debug and then use that in an assert statement to print out some values while debugging, similar to the code shown below (or as seen on github). In the final version, debug would then be set to false. Would that slow down the simulation or does the assert get eliminated, because debug is a constant? model debugexample parameter Real a; parameter Real b; Real sum; protected final constant Boolean debug = false "set to true while