numbers

问题 I'm trying to make a generic function that takes any type of Number and conditionally does something if that number is equal to zero. I want anyone to be able to pass it any of the classes that extend Number (BigDecimal, BigInteger, Byte, Double, Float, Integer, Long, or Short) So far, I've attempted to use instanceof to find out what type the number is, then compare it to an equivalent type public static boolean isZero(Number number) { if (number instanceof BigDecimal) { return BigDecimal

问题 I have a method like this: Prefix GetPrefix(decimal value) { if(value > 11000000000000000000) return Prefix.CosmicBig; if(value > 1000000000000000) return Prefix.ReallyBig; if(value > 3000000000000) return Prefix.Big; if(value > 50000000) return Prefix.Okay; if(value > 750000) return Prefix.MostlyNormal; if(value > 750000) return Prefix.SoSo; if(value > 750) return Prefix.Small; return Prefix.MiserablySmall; } The exact values are not important. What matters is that they are sometimes changed

问题 Like we use fermat's little theorem for modular exponentiation , I was just wondering that is there any such method for fast matrix exponentiation ? Can we use fermat's theorem for matrix exponentiation ? If no then is there any faster method than divide and conquer method of exponentiation ? 回答1: I would look for Octave's implementation of that. There it gives you some references. Here some links: http://epubs.siam.org/doi/abs/10.1137/1020098 http://www.cs.cornell.edu/cv/researchpdf/19ways+

问题 I was trying to work with the codeigniter pagination class. Here is my code $this->load->library('pagination'); $config['base_url'] = base_url('language/'.$this->uri->segment(2)); $config['total_rows'] = $page_count; $config['per_page'] = 1; $config['num_links'] = '2'; $config['uri_segment'] = '2'; $this->pagination->initialize($config); $data['pages'] = $this->pagination->create_links(); but then, in the first page, the url would be look like localhost/language/something/ while the second

问题 For the following code snippet: $a = '5 USD'; $b = 10; echo $a + $b; The answer is 15. But in the variable $a if 5 is in between 'USD' or after 'USD' the output is 10 . Why it is so? Can somebody explain? 回答1: From php.net: When a string is evaluated in a numeric context, the resulting value and type are determined as follows. If the string does not contain any of the characters '.', 'e', or 'E' and the numeric value fits into integer type limits (as defined by PHP_INT_MAX), the string will

问题 I'm writing convenience methods to check if number is positive or negative like so: class Numeric def positive? self > 0 end def negative? self < 0 end end but in this case I do not know how to handle cases like these: >> 0.positive? >> 0.negative? Update : I've updated the typo in the class name. I used numeric because I needed to check the floats as well. 回答1: If the problem is that you're getting false for both, either you consider 0 to be positive or not. If so, you should have something

问题 I'm trying to create a function using mt_rand() in order to generate a truly random number, since rand() just isn't suffice. The problem is I need to pre-define the length of the number, say I need a 10 digit random number. Anyway, I've been messing around and this is what I've come up with: function randomNumber($length) { $min = str_repeat(0, $length-1) . 1; $max = str_repeat(9, $length); return mt_rand($min, $max); } In theory that should work (as far as I can tell), but it doesn't. The

问题 I want to give our users in the database a unique alpha-numeric id. I am using the code below, will this always generate a unique id? Below is the updated version of the code: old php: // Generate Guid function NewGuid() { $s = strtoupper(md5(uniqid(rand(),true))); $guidText = substr($s,0,8) . '-' . substr($s,8,4) . '-' . substr($s,12,4). '-' . substr($s,16,4). '-' . substr($s,20); return $guidText; } // End Generate Guid $Guid = NewGuid(); echo $Guid; echo "<br><br><br>"; New PHP: //

问题 Apparently this is suposed to work in showing if a string is numerical, for example "12.5" == yes, "abc" == no. However I get a no reguardless of the input. std::stringstream ss("2"); double d; ss >> d; if(ss.good()) {std::cout<<"number"<<std::endl;} else {std::cout<<"other"<<std::endl;} 回答1: You should use an istringstream so that it knows it's trying to parse input. Also, just check the result of the extraction directly rather than using good later. #include <sstream> #include <iostream>

问题 I'm reading the Number Type section of the book Professional JavaScript for Web Developers . It seems to say that all ECMAScript numbers are binary64 floating point, which is corroborated by this MDN article. But the book author also says: Because storing floating-point values uses twice as much memory as storing integer values, ECMAScript always looks for ways to convert values into integers. I expected numbers to each occupy the same amount of memory: 64 bits. And the MDN article says,