integer

问题 This question already has answers here : Determine if object is integer (3 answers) Closed 2 years ago . I'm using some API by restTemplate. The API returns a key whose type is integer. But I'm not sure of that value, so I want to check whether the key is really an integer or not. I think it might be a string. What is the best way of checking if the value is really integer? added: I mean that some API might return value like below. {id : 10} or {id : "10"} 回答1: Object x = someApi(); if (x

问题 ( note : not the same as this other question since the OP never explicitly specified rounding towards 0 or -Infinity) JLS 15.17.2 says that integer division rounds towards zero. If I want floor() -like behavior for positive divisors (I don't care about the behavior for negative divisors), what's the simplest way to achieve this that is numerically correct for all inputs? int ifloor(int n, int d) { /* returns q such that n = d*q + r where 0 <= r < d * for all integer n, d where d > 0 * * d = 0

问题 I'm building a index which is just several sets of ordered 32 bit integers stored continuously in a binary file. The problem is that this file grows pretty large. I've been thinking of adding some compressions scheme but that's a bit out of my expertise. So I'm wondering, what compression algorithm would work best in this case? Also, decompression has to be fast since this index will be used to make make look ups. 回答1: If you are storing integers which are close together (eg: 1, 3 ,4, 5, 9,

问题 There are a couple of ways to find integer square roots using only integer arithmetic. For example this one. It makes for interesting reading and also a very interesting theory, particularly for my generation where such techniques aren't so useful any more. The main thing is that it can't use floating point arithmetic, so that rules out newtons method and it's derivations. The only other way I know of to find roots is binomial expansion, but that also requires floating point arithmetic. What

问题 Does PHP have a built in function for doing string to integer hashes, something that's difficult to reverse? Now, I know I can probably get away with doing an md5, and treating a substring of it as a radix 16 number, but I'm looking for something built in. Thanks. 回答1: I think the best bet would chose a standard hash [either md5() or sha1() ] to obtain a hash of your string, and then to get an integer hash, to a base_convert($hash, 16, 10) and that should convert your hash into a integer hash

问题 For my work it's particularly interesting to do integer calculations, which obviously are not what GPUs were made for. My question is: Do modern GPUs support efficient integer operations? I realize this should be easy to figure out for myself, but I find conflicting answers (for example yes vs no), so I thought it best to ask. Also, are there any libraries/techniques for arbitrary precision integers on GPUs? 回答1: First, you need to consider the hardware you're using: GPU devices performance

问题 Perl usually converts numeric to string values and vice versa transparently. Yet there must be something which allows e.g. Data::Dumper to discriminate between both, as in this example: use Data::Dumper; print Dumper('1', 1); # output: $VAR1 = '1'; $VAR2 = 1; Is there a Perl function which allows me to discriminate in a similar way whether a scalar's value is stored as number or as string? 回答1: There's no way to find this out using pure perl. Data::Dumper uses a C library to achieve it. If

问题 Does Lua make use of 64-bit integers? How do I use it? 回答1: Compile it yourself. Lua uses double-precision floating point numbers by default. However, this can be changed in the source ( luaconf.h , look for LUA_NUMBER ). 回答2: require "bit" -- Lua unsigned 64bit emulated bitwises -- Slow. But it works. function i64(v) local o = {}; o.l = v; o.h = 0; return o; end -- constructor +assign 32-bit value function i64_ax(h,l) local o = {}; o.l = l; o.h = h; return o; end -- +assign 64-bit v.as 2

问题 Say I have an array of positive whole integers; I'd like to manipulate the order so that the concatenation of the resultant array is the largest number possible. For example [97, 9, 13] results in 99713 ; [9,1,95,17,5] results in 9955171 . I'm not sure of an answer. 回答1: sorted(x, cmp=lambda a, b: -1 if str(b)+str(a) < str(a)+str(b) else 1) 回答2: Intuitively, we can see that a reverse sort of single digit numbers would lead to the higest number: >>> ''.join(sorted(['1', '5', '2', '9'], reverse

问题 I have a binary string, entered by the user, which I need to convert to an integer. At first I naivly used this simple line: Convert.ToInt32("11011",2); Unfortunately this throws an exception if the user enters the integer directly. Convert.ToInt32("123",2); // throws Exception How can I make sure that the string entered by the user actually is a binary string? try..catch....but that's just too ugly. something like 'Int32.TryParse' maybe. Thanks 回答1: You could use a Regex to check that it is