bitwise-operators

问题 This question already has answers here : Arithmetic right shift gives bogus result? (2 answers) Is right shift undefined behavior if the count is larger than the width of the type? (2 answers) Closed 4 years ago . Can't understand behavior of this bit shift: int container = 1; cout<<(container>>32)<<endl; If it's logical shift the output should be 0, but it's 1 instead, as if it was cyclic shift. When looking at disassembly I see that command used is SAR. Please explain this behavior to me.

问题 Assume you have a binary tree which classifies images. Each node is a different binary test. When an image is fed to the tree, a unique path through the tree is generated. A path is described as a binary word which is as long as the depth of the tree. For instance, for a 2-stage binary tree, an example of path would be (0,1) ((left,right) thus ending in the second leaf of the tree from the left). We also assume that for any image being fed to the tree, all node tests are executable. Thus, we

问题 I want to convert a vector of signed char into a vector of unsigned char. I want to preserve the value range for each type. I mean the value range of signed char is -128 and +127 when the value range of an unsigned char element is between 0 - 255. Without intrinsics I can do this almost like that : #include <iostream> int main(int argc,char* argv[]) { typedef signed char schar; typedef unsigned char uchar; schar a[]={-1,-2,-3,4,5,6,-7,-8,9,10,-11,12,13,14,15,16,17,-128,19,20,21,22,23,24,25,26

问题 Is there a way to pick a value based on the bit position. The problem statement is:- for a 16 bits position, I can set any bits, say I set 1,4,6,7,11,13 bit so the mask would be:- Bit Positons 0 0 1 0 1 0 0 0 1 1 0 1 0 0 1 0 Now I need to randomly pick a value based on this bit mask, where only 1 bit is set, so my possible values could be:- For selecting 4 :0 0 0 0 0 0 0 0 0 0 0 1 0 0 0 0 For Selecting 7: 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 But I need to select this value randomly, so I though of

问题 I'm curious to find what the fastest algorithm is for returning the position of the least significant bit set in an integer in Python 3. Are there algorithms faster than this one in Python 3? Any enhancements one could use to speed things up? def lsb(n): temp = n & -n pos = -1 while temp: temp >>= 1 pos += 1 return(pos) 回答1: summarizing, since this is for python3 and so not an exact duplicate of return index of least significant bit in Python (although there are other applicable answers there

问题 Working on a class assignment, I'm trying to cast an integer to a float only using bit manipulations (limited to any integer/unsigned operations incl. ||, &&. also if, while). My code is working for most values, but some values are not generating the results I'm looking for. For example, if x is 0x807fffff, I get 0xceff0001, but the correct result should be 0xceff0000. I think I'm missing something with my mantissa and rounding, but can't quite pin it down. I've looked at some other threads

问题 in refereing to bit-wise operators, what is the difference between ! and ~ ? I feel like they both flip the bits, but 1 maybe adds a 1 to the final answer? ~0xC4 compared to !0xC4 Thanks! 回答1: ! is not a bitwise operator, it's a boolean operator. The boolean operators operate on truth values, which are generally int . Any non-zero value is true, while 0 is false. The result is always 1 for true, 0 for false. ! is boolean not && is boolean and || is boolean or These are the ones used in e.g.

问题 I have the following TypedArray (note that the size of this data is 80 bits): var arr = new Uint8Array([10, 110, 206, 117, 200, 35, 99, 2, 98, 125]); and I want to rotate it by N bits (where N is any integer from 0 to 79). For example, if N=50, I will represent it like this: 00001010 01101110 11001110 01110101 11001000 00100011 01100011 00000010 01100010 01111101 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ so the result should be 01101100 01100000 01001100 01001111 10100001 01001101

问题 A little context, I was looking at another SO post when I am trying to solve javascript problem to find all possible subsets. I am not asking about the JS challenge, but why it was there and what mathematical significance does it have? Here is the copy paste of the code from this SO post var arr = [1, 2, 3]; function generatePowerSet(array) { var result = []; result.push([]); for (var i = 1; i < Math.pow(2, array.length); i++, result.push(subset)) for (var j = 0, subset = []; j < array.length

问题 var = 86 print((var < 90) & (var >= 80)) prints True . But why do all these print False ? print(var < 90 & var >= 80) print(var < 90 & (var >= 80)) print((var < 90) & var >= 80) print(var < 90 & True) 回答1: You should be using the and operator instead for boolean operations. Since python supports chaining relational operators (i.e. you can use 0 < var < 100 instead of 0 < var and var < 100 ) and processes binary operations (i.e. addition, subtraction, bitwise operations, etc.) before