3,111 questions
2
votes
3
answers
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Bitwise operations act outside of type width in C; Compiler Bug or Within Spec?
The following derives from this question but is distinct
Consider the following code sample;
uint32_t *value = malloc(sizeof(uint32_t));
*value = 0xAAAABBBB;
int16_t *subset = (int16_t*) (value);
...
1
vote
2
answers
183
views
Why we use PIN & (1<<PBx) to check if PIN is high?
I'm a beginner working on AVR programming on the ATmega328P. I am trying to get input from a button and then control an LED.
void setup() {
DDRB |= (1<<PB5);
DDRB &= ~(1<<PB4);
...
2
votes
2
answers
212
views
Bitwise division in C : Programme seems to work for other numbers but when the divisor is 0 it returns 11 for no apparent reason
I am trying to solve the problem posed in this question which asks that division of two numbers be performed in a bitwise manner. So, I wrote the following functions.
sum() adds two numbers.
larger() ...
- 469
1
vote
1
answer
81
views
Bitwise operator or converts uints to int in golang
In a golang project I have defined those uints. They are set to uint automatically by iota:
package userrole
const (
Reviewee = 1 << iota // 1
Reviewer // 2
Admin ...
- 1,487
5
votes
3
answers
273
views
Finding the bigger number using bitwise operation in C
I am trying to write a computer programme that will take two numbers from the user as inputs and will print the bigger number using bitwise operation. I want it to end the programme and return 1 if ...
- 469
3
votes
2
answers
183
views
Programme works but says "warning: integer constant is so large that it is unsigned", solution?
I am trying solve the problem posed in this question that asks << 1 operation be performed on a 64 bit number using NAND operation only and without using any arithmetic operation. My attempted ...
- 469
0
votes
0
answers
24
views
Detecting overflow in two’s complement multiplication by 2 – which bits need to be checked
Given a number with a width of n bits representing a signed number in two's complement, what is the minimal number of bits that need to be checked and which ones, in order to know whether there will ...
0
votes
0
answers
76
views
Which of these two bitwise expressions is faster, and is there an optimized alternative?
I have two bitwise expressions and need to figure out which one is faster. Also, if there are other ways to implement the same, but in a faster way than the given expression. I am using these ...
- 1
4
votes
2
answers
205
views
Shift "<<" and bitwise "&" operators precedence issue. Why it doesn't compile?
This code doesn't compile.
It seems like the compiler (VS) is interpreting the expression as:
(std::cout << ul1) & (ul2 << std::endl)
#include <iostream>
int main() {
...
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0
votes
0
answers
54
views
How to BIT inverse a value in OpenOffice Calc?
I need to bit inverse a value in a cell. All I found was the function XOR(a;b) and it would be possible to use a bitwise XOR to invert a value. However, the problem is that that XOR(a;b) only does a ...
- 5,861
-1
votes
1
answer
54
views
Assembly: Character type checking
So I'm practicing disassembling on an C program that checks if the user given serial number fulfills the requirements.
The program manually checks each character from the serial number, executing the ...
- 13
1
vote
1
answer
110
views
right shift not working correctly for large longs
when shifting bytes, there are some scenarios that do not seem to make sense, for example
printf("shifted bytes %llx\n",(((long long)1 << 63 ))>>1);
outputs c000000000000000, ...
- 103
-2
votes
1
answer
35
views
Salesforce Bitwise Comparison
I have a field containing an int that represents flags
0 = No error
1 = Error 1
2 = Error 2
4 = Error 3
8 = Error 4
so if I have a value of 5, I know it is Error 1 and Error 3
I need to add custom ...
- 1,117
-1
votes
2
answers
136
views
Unexpected output from right rotate function
I was trying to solve the exercise that says
Exercise 2-7. Write the function rightrot(b, n) which rotates the integer b to the right by n bit positions.
and i did code it, here is the code
#include ...
-2
votes
1
answer
94
views
Using bitwise operations to simulate an N-length hash table: is space complexity O(1) or O(n)? [closed]
I am solving a problem that requires O(1) space complexity to check for duplicate numbers. I wanted to use a hash table, but due to the O(1) space constraint, I used bitwise operations. However, I ...
- 115