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  • Efficient bitshifting an array of int?

    - by nn
    Hi, To be on the same page, let's assume sizeof(int)=4 and sizeof(long)=8. Given an array of integers, what would be an efficient method to bitshift the array to either the left or right? I am contemplating an auxiliary variable such as a long, that will compute the bitshift for the first pair of elements (index 0 and 1) and set the first element (0). Continuing in this fashion the bitshift for elements (index 1 and 2) will be computer, and then index 1 will be set. I think this is actually a fairly efficient method, but there are drawbacks. I cannot bitshift greater than 32 bits. I think using multiple auxiliary variables would work, but I'm envisioning recursion somewhere along the line.

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  • Remove leading zero's from alphanumeic text

    - by cedar715
    I've seen questions to prefix zeros here in SO. But not the other way !! Can you guys suggest me how to remove the leading zeros in alphanumeric text. Are there any built-in APIs or do I need to write a method to trim the leading zero's? Example: 01234 converts to 1234 0001234a converts to 1234a 001234-a converts to 1234-a 101234 remains as 101234 2509398 remains as 2509398 123z remains as 123z 000002829839 converts to 2829839

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  • Are there any way to apply regexp in java ignoring letter case?

    - by Roman
    Simple example: we have string "Some sample string Of Text". And I want to filter out all stop words (i.e. "some" and "of") but I don't want to change letter case of other words which should be retained. If letter case was unimportant I would do this: str.toLowerCase().replaceAll ("a|the|of|some|any", ""); Is there an "ignore case" solution with regular expressions in java?

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  • How to fill a section within c++ string?

    - by stacker
    Having a string of whitespaces: string *str = new string(); str->resize(width,' '); I'd like to fill length chars at a position. In C it would look like memset(&str[pos],'#', length ); How can i achieve this with c++ string, I tried string& assign( const string& str, size_type index, size_type len ); but this seems to truncat the original string. Is there an easy C++ way to do this? Thanks.

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  • How to manually (bitwise) perform (float)x? (homework)

    - by Silver
    Now, here is the function header of the function I'm supposed to implement: /* * float_from_int - Return bit-level equivalent of expression (float) x * Result is returned as unsigned int, but * it is to be interpreted as the bit-level representation of a * single-precision floating point values. * Legal ops: Any integer/unsigned operations incl. ||, &&. also if, while * Max ops: 30 * Rating: 4 */ unsigned float_from_int(int x) { ... } We aren't allowed to do float operations, or any kind of casting. Now I tried to implement the first algorithm given at this site: http://locklessinc.com/articles/i2f/ Here's my code: unsigned float_from_int(int x) { // grab sign bit int xIsNegative = 0; int absValOfX = x; if(x < 0){ xIsNegative = 1; absValOfX = -x; } // zero case if(x == 0){ return 0; } //int shiftsNeeded = 0; /*while(){ shiftsNeeded++; }*/ unsigned I2F_MAX_BITS = 15; unsigned I2F_MAX_INPUT = ((1 << I2F_MAX_BITS) - 1); unsigned I2F_SHIFT = (24 - I2F_MAX_BITS); unsigned result, i, exponent, fraction; if ((absValOfX & I2F_MAX_INPUT) == 0) result = 0; else { exponent = 126 + I2F_MAX_BITS; fraction = (absValOfX & I2F_MAX_INPUT) << I2F_SHIFT; i = 0; while(i < I2F_MAX_BITS) { if (fraction & 0x800000) break; else { fraction = fraction << 1; exponent = exponent - 1; } i++; } result = (xIsNegative << 31) | exponent << 23 | (fraction & 0x7fffff); } return result; } But it didn't work (see test error below): Test float_from_int(-2147483648[0x80000000]) failed... ...Gives 0[0x0]. Should be -822083584[0xcf000000] 4 4 0 float_times_four I don't know where to go from here. How should I go about parsing the float from this int?

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  • when to use StringBuilder in java

    - by kostja
    It is supposed to be generally preferable to use a StringBuilder for String concatenation in Java. Is it always the case? What i mean is : Is the overhead of creating a StringBuilder object, calling the append() method and finally toString() smaller then concatenating existing Strings with + for 2 Strings already or is it only advisable for more Strings? If there is such a threshold, what does it depend on (the String length i suppose, but in which way)? And finally - would you trade the readability and conciseness of the + concatenation for the performance of the StringBuilder in smaller cases like 2, 3, 4 Strings?

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  • Masking a bit in C returning unexpected result

    - by Eamorr
    0x7F000000 is 0111 1111 0000 0000 0000 0000 0000 0000 in 32 bit binary. 0x01000058 is 0000 0001 0000 0000 0000 0000 0101 1000. When I AND the two numbers together I expect 0000 0001 0000 0000 0000 0000 0000 0000, but for some reason I get 0. Here is my code: #define MASK_binop 0x80000000 #define MASK_operation 0x7F000000 int instruction=atoi(line); if((MASK_binop & instruction)>0) printf("binop\n"); else if((MASK_operation & instruction)>0) printf("operation\n"); Each of the above comparisons keeps returning zero. Is it something to do with 32/64 bits? I'm using 64-bit compiler.

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  • How to invert alternate bits of a number

    - by Cupidvogel
    The problem is how to invert alternate bits of a number, starting from the LSB. Currently what I am doing is first doing a count = -1 while n: n >>= 1 count += 1 to first find the position of the leftmost set bit, then running a loop to invert every alternate bit: i = 0 while i <= count: num ^= 1<<i i += 2 Is there a quick hack solution instead of this rather boring loop solution? Of course, the solution can't make any asumption about the size of the integer.

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  • Getting value of LSB from Hex (C code)

    - by Rjff
    Hi - first post here :) I've got a code like this in C: unsigned char const data[ ] = {0x0a, 0x1d, 0xf0, 0x07}; I need to extract it such that the final value is: 0xa1df7 I have only been able to extract and get it working if the hex values that have at least 1 zero: unsigned char const data[ ] = {0x0a, 0xd0, 0xf0, 0x07}; using the code below: for(int i = 0; i < SIZE; ++i) { tmp = data[i]; if ( (data[i] <= 0x0F) && (((data[i] & 0x0F) == 0) || (data[i] & 0xF0) == 0)) // one of the hex is zero { tmp = ((tmp << 4) >> 4) << N[i]; std::cout << "foo: " << std::hex << tmp << ":" << std::endl; } else if ((data[i] >= 0x0F) && (((data[i] & 0x0F) == 0) || (data[i] & 0xF0) == 0) ) { tmp = (tmp >> 4) << N[i]; std::cout << "bar: " << std::hex << tmp << ":" << std::endl; } else { std::cout << "result: " << std::hex << result << ":" << std::endl; std::cout << "tmp << 8: " << std::hex << (tmp << 8)<< ":" << std::endl; result = result | (tmp << 8); std::cout << "result |= (tmp << 8): " << std::hex << result << ":" << std::endl; } result |= tmp; std::cout << "boo: " << std::hex << result << ":" << std::endl; } It seems the last else {...} block is troublesome for me. Any ideas? Thanks!

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  • How to convert from string to a number, and vice-versa in C++?

    - by Igal
    DEAR All I'm new to the C++, so maybe someone can say what the proper way to write a function that gets a string char (represents number) and converts it to the integer number. For example : input : Sixty five, output: 65. Maybe it should use by cin.getline() ? Well, vice-versa is little bit simlper... Thanks for advance. Igal

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  • parse this directory path without losing slash

    - by PPTim
    hi, I have a wxPython application. I am taking in a directory path from a textbox using GetValue(). I notice that while trying to parse in the directory path "C:\Documents and Settings\UserName\Desktop\InputFile.xls", python sees the string as 'C:\\Documents and Settings\UserName\\Desktop\\InputFile.xls' (missing a slash between "Settings" and "UserName). Why is it that only that slash is not correctly escaped? Once the string has been changed to 'C:\Documents and Settings\UserName\Desktop\InputFile.xls', is there a type conversion or function that can does this properly? Thanks.

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  • BufferedImage & ColorModel in Java

    - by spol
    I am using a image processing library in java to manipulate images.The first step I do is I read an image and create a java.awt.Image.BufferedImage object. I do it in this way, BufferedImage sourceImage = ImageIO.read( new File( filePath ) ); The above code creates a BufferedImage ojbect with a DirectColorModel: rmask=ff0000 gmask=ff00 bmask=ff amask=0. This is what happens when I run the above code on my macbook. But when I run this same code on a linux machine (hosted server), this creates a BufferedImage object with ColorModel: #pixelBits = 24 numComponents = 3 color space = java.awt.color.ICC_ColorSpace@c39a20 transparency = 1 has alpha = false isAlphaPre = false. And I use the same jpg image in both the cases. I don't know why the color model on the same image is different when run on mac and linux. The colormodel for mac has 4 components and the colormodel for linux has 3 components.There is a problem arising because of this, the image processing library that I use always assumes that there are always 4 components in the colormodel of the image passed, and it throws array out of bounds exception when run on linux box. But on macbook, it runs fine. I am not sure if I am doing something wrong or there is a problem with the library. Please let me know your thoughts. Also ask me any questions if I am not making sense!

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  • GDI+, using DrawImage to draw a transperancy mask of the source image

    - by sold
    Is it possible to draw a transperancy mask of an image (that is, paint all visible pixels with a constant color) using Graphics::DrawImage? I am not looking for manually scanning the image pixel-by-pixel and creating a seperate mask image, I wonder if it's possible to draw one directly from the original image. My guessing is that it should be done with certain manipulations to ImageAttributes, if possible at all. The color of the mask is arbitrary and should be accurate, and it would be a plus if there can be a threshold value for the transparency.

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  • Convert Text with newlines to a List<String>

    - by Vaccano
    I need a way to take a list of numbers in string form to a List object. Here is an example: string ids = "10\r\n11\r\n12\r\n13\r\n14\r\n15\r\n16\r\n17\r\n18\r\n19"; List<String> idList = new List<String>(); idList.SomeCoolMethodToParseTheText(ids); <------+ | foreach (string id in idList) | { | // Do stuff with each id. | } | | // This is the Method that I need ----------------+ Is there something in the .net library so that I don't have to write the SomeCoolMethodToParseTheText myself?

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  • Find most significant bit (left-most) that is set in a bit array

    - by Claudiu
    I have a bit array implementation where the 0th index is the MSB of the first byte in an array, the 8th index is the MSB of the second byte, etc... What's a fast way to find the first bit that is set in this bit array? All the related solutions I have looked up find the first least significant bit, but I need the first most significant one. So, given 0x00A1, I want 9.

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  • How to detect padding on an integer and treat it as a string?

    - by Sirber
    I have this function to prepare variable to be used in a SQL query: function sqlize($mInput) { if (!isset($mInput)) $mInput = "null"; elseif (strtolower($mInput) == "null") { } elseif (is_numeric($mInput)) { } elseif (is_string($mInput)) { $mInput = trim($mInput); $mInput = addslashes($mInput); $mInput = '"' . $mInput . '"'; } else $mInput = "null"; return $mInput; } I have a string "0004", which is going in a "varchar field", is cought by is_numeric, and is saved as "4" and not "0004". Is there a way to detect the padding and process it as a string? Thank you!

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  • Drawbacks of using an integer as a bitfield?

    - by Mark
    I have a bunch of boolean options for things like "accepted payment types" which can include things like cash, credit card, cheque, paypal, etc. Rather than having a half dozen booleans in my DB, I can just use an integer and assign each payment method an integer, like so PAYMENT_METHODS = ( (1<<0, 'Cash'), (1<<1, 'Credit Card'), (1<<2, 'Cheque'), (1<<3, 'Other'), ) and then query the specific bit in python to retrieve the flag. I know this means the database can't index by specific flags, but are there any other drawbacks?

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  • escape double quote in vb string

    - by JKS
    i have used following piece of code to execute schtasks command from vb6 while executing it ignores folder if it contains space For example "C:\program files\test\test.exe" will be converted to "c:\program " how do i solve this issue? MyAppname = Chr(34) & App.Path & "\" & App.EXEName & ".exe" & Chr(34) StrCommand = "schtasks /create /sc ONLOGON /RL HIGHEST /tn myapp /tr " & MyAppname Shell StrCommand, vbHide thanks in advance

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  • Manipulating both unicode and ASCII character set in C#

    - by Murlex
    I have this mapping in my C# application string [,] unicode2Ascii = { { "&#3001;", "\x86" } }; ஹ - is the unicode value for a tamil literal "ஹ". This is the raw hex literal for the unicode value saved by MS Word as a byte sequence. I am trying to map these unicode value "strings" to a hex value under 255 (so as to accommodate non-unicode supported systems). I trying to use string.replace like this: S = S.replace(unicode2Ascii[0,0], unicode2Ascii[0,1]); However the resultant ouput has a ? instead of the actual hex 0x86 stored. Any pointer on how I could set the encoding for the second element of that array to something like windows-1252? Or is there a better way to do this conversion? thanks in advance

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