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  • Convert bit vector (array of booleans) to an integer, and integer to bit vector, in Java.

    - by dreeves
    What's the best way to unstub the following functions? // Convert a bit-vector to an integer. int bitvec2int(boolean[] b) { [CODE HERE] } // Convert an integer x to an n-element bit-vector. boolean[] int2bitvec(int x, int n) { [CODE HERE] } Or is there a better way to do that sort of thing than passing boolean arrays around? This comes up in an Android app where we need an array of 20 booleans to persist and the easiest way to do that is to write an integer or string to the key-value store. I'll post the way we (Bee and I) wrote the above as an answer. Thanks!

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  • C++ converting hexadecimal md5 hash to decimal integer

    - by Zackery
    I'm doing Elgamal Signature Scheme and I need to use the decimal hash value from the message to compute S for signature generation. string hash = md5(message); cout << hash << endl; NTL::ZZ msgHash = strtol(hash.c_str(), NULL, 16); cout << msgHash << endl; There are no integer large enough to contain the value of 32 byte hexadecimal hash, and so I tried big integer from NTL library but it didn't work out because you cannot assign long integer to NTL::ZZ type. Is there any good solution to this? I'm doing this with visual C++ in Visual Studio 2013.

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  • Disabling identity (auto-incrementing) on integer primary key using code first

    - by gw0
    I am using code first approach in a ASP.NET MVC 3 application and all integer primary keys in models (public int Id { get; set; }) are by default configured as an identity with auto-incrementing. How to disable this and enable a way to manually enter the integer for the primary key? The actual situation is that the Id integers have a special meaning and I would therefore like to have them choosable at creation and later editable. It would be ideal if in case the integer is not given at creation time it is auto-incremented, else the specified value is used. But editable primary fields is my primary need. Is there any way to do this elegantly in ASP.NET MVC 3?

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  • String as \x03\x00\x00\x00 to integer

    - by marta
    Helo: I have a question, that I solved in c, but now I want to do it in hava: I have a String like: '\x03\x00\x00\x00' This is representing an hexadecimal value of a integer. I transform to 0x03\0x00... And now I want to obtain the integer, but I don't know how to do it in java could someone give me some idea ? Thanks in advance (Is it some way to use this format ('\x03\x00\x00\x00' ) directly without use byte[] arrays? and in C can I use this format directly to build a integer (int)?)

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  • Why is DivMod Limited to Words (<=65535)?

    - by Andreas Rejbrand
    In Delphi, the declaration of the DivMod function is procedure DivMod(Dividend: Cardinal; Divisor: Word; var Result, Remainder: Word); Thus, the divisor, result, and remainder cannot be grater than 65535, a rather severe limitation. Why is this? Why couldn't the delcaration be procedure DivMod(Dividend: Cardinal; Divisor: Cardinal; var Result, Remainder: Cardinal); The procedure is implemented using assembly, and is therefore probably extremely fast. Would it not be possible for the code PUSH EBX MOV EBX,EDX MOV EDX,EAX SHR EDX,16 DIV BX MOV EBX,Remainder MOV [ECX],AX MOV [EBX],DX POP EBX to be adapted to cardinals? How much slower is the naïve attempt procedure DivModInt(const Dividend: integer; const Divisor: integer; out result: integer; out remainder: integer); begin result := Dividend div Divisor; remainder := Dividend mod Divisor; end; that is not (?) limited to 16-bit integers?

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  • Division by zero: Undefined Behavior or Implementation Defined in C and/or C++ ?

    - by SiegeX
    Regarding division by zero, the standards say: C99 6.5.5p5 - The result of the / operator is the quotient from the division of the first operand by the second; the result of the % operator is the remainder. In both operations, if the value of the second operand is zero, the behavior is undefined. C++03 5.6.4 - The binary / operator yields the quotient, and the binary % operator yields the remainder from the division of the first expression by the second. If the second operand of / or % is zero the behavior is undefined. If we were to take the above paragraphs at face value, the answer is clearly Undefined Behavior for both languages. However, if we look further down in the C99 standard we see the following paragraph which appears to be contradictory(1): C99 7.12p4 - The macro INFINITY expands to a constant expression of type float representing positive or unsigned infinity, if available; Do the standards have some sort of golden rule where Undefined Behavior cannot be superseded by a (potentially) contradictory statement? Barring that, I don't think it's unreasonable to conclude that if your implementation defines the INFINITY macro, division by zero is defined to be such. However, if your implementation does not define such a macro, the behavior is Undefined. I'm curious what the consensus on this matter for each of the two languages. Would the answer change if we are talking about integer division int i = 1 / 0 versus floating point division float i = 1.0 / 0.0 ? Note (1) The C++03 standard talks about the library which includes the INFINITY macro.

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  • PHP validating integers

    - by Mikk
    Hi, I was wondering, what would be the best way to validate an integer. I'd like this to work with strings as well, so I could to something like (string)+00003 - (int)3 (valid) (string)-027 - (int)-27 (valid) (int)33 - (int)33 (valid) (string)'33a' - (FALSE) (invalid) That is what i've go so far: function parseInt($int){ //If $int already is integer, return it if(is_int($int)){return $int;} //If not, convert it to string $int=(string)$int; //If we have '+' or '-' at the beginning of the string, remove them $validate = ($int[0] === '-' || $int[0] === '+')?substr($int, 1):$int; //If $validate matches pattern 0-9 convert $int to integer and return it //otherwise return false return preg_match('/^[0-9]+$/', $validate)?(int)$int:FALSE; } As far as I tested, this function works, but it looks like a clumsy workaround. Is there any better way to write this kind of function. I've also tried filter_var($foo, FILTER_VALIDATE_INT); but it won't accept values like '0003', '-0' etc.

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  • Strange Integer.parseInt exception

    - by Albinoswordfish
    Exception in thread "Thread-2" java.lang.NumberFormatException: For input string: "3" int test = Integer.parseInt(result[0]); This is the error I keep getting when I'm trying to convert "3" to an integer. Well I'm receiving this "3" through a RS-232 port, so maybe this is what is causing the error. If anybody has any idea what could be causing this it would be appreciated.

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  • scala integer weirdness

    - by williamstw
    Suppose you inadvertently use Integer instead of Int, as in this code: import scala.collection.mutable.Map val contributors = Map[String,Integer]() val count = contributors.getOrElseUpdate("john",0) contributors.put("john",count+1) println(contributors) Compiler output: (fragment of test.scala):7: error: type mismatch; found : Int(1) required: String contributors.put("john",count+1) ^ Why "required: String"?

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  • ABAP - increment an integer

    - by Ben
    Hi there, sometimes ABAP drives me crazy with really simple tasks - as incrementing an integer within a loop... Here's my try: METHOD test. DATA: lv_id TYPE integer. lv_id = 1. LOOP AT x ASSIGNING <y>. lv_id = lv_id+1. ENDLOOP. ENDMETHOD. This gives me a strange error I can hardly translate to english..

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  • Find maximum positive integer value in Bourne Shell

    - by l0b0
    I'm checking a counter in a loop to determine if it's larger than some maximum, if specified in an optional parameter. Since it's optional, I can either default the maximum to a special value or to the maximum possible integer. The first option would require an extra check at each iteration, so I'd like to instead find out what is the maximum integer that will work with the -gt Bourne Shell operation.

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  • Finding N contiguous zero bits in an integer to the left of the MSB position of another integer

    - by James Morris
    The problem is: given an integer val1 find the position of the highest bit set (Most Significant Bit) then, given a second integer val2 find a contiguous region of unset bits, with the minimum number of zero bits given by width to the left of the position (ie, in the higher bits). Here is the C code for my solution: typedef unsigned int t; unsigned const t_bits = sizeof(t) * CHAR_BIT; _Bool test_fit_within_left_of_msb( unsigned width, t val1, t val2, unsigned* offset_result) { unsigned offbit = 0; unsigned msb = 0; t mask; t b; while(val1 >>= 1) ++msb; while(offbit + width < t_bits - msb) { mask = (((t)1 << width) - 1) << (t_bits - width - offbit); b = val2 & mask; if (!b) { *offset_result = offbit; return true; } if (offbit++) /* this conditional bothers me! */ b <<= offbit - 1; while(b <<= 1) offbit++; } return false; } Aside from faster ways of finding the MSB of the first integer, the commented test for a zero offbit seems a bit extraneous, but necessary to skip the highest bit of type t if it is set. I have also implemented similar algorithms but working to the right of the MSB of the first number, so they don't require this seemingly extra condition. How can I get rid of this extra condition, or even, are there far more optimal solutions? Edit: Some background not strictly required. The offset result is a count of bits from the high bit, not from the low bit as maybe expected. This will be part of a wider algorithm which scans a 2D array for a 2D area of zero bits. Here, for testing, the algorithm has been simplified. val1 represents the first integer which does not have all bits set found in a row of the 2D array. From this the 2D version would scan down which is what val2 represents. Here's some output showing success and failure: t_bits:32 t_high: 10000000000000000000000000000000 ( 2147483648 ) --------- ----------------------------------- *** fit within left of msb test *** ----------------------------------- val1: 00000000000000000000000010000000 ( 128 ) val2: 01000001000100000000100100001001 ( 1091569929 ) msb: 7 offbit:0 + width: 8 = 8 mask: 11111111000000000000000000000000 ( 4278190080 ) b: 01000001000000000000000000000000 ( 1090519040 ) offbit:8 + width: 8 = 16 mask: 00000000111111110000000000000000 ( 16711680 ) b: 00000000000100000000000000000000 ( 1048576 ) offbit:12 + width: 8 = 20 mask: 00000000000011111111000000000000 ( 1044480 ) b: 00000000000000000000000000000000 ( 0 ) offbit:12 iters:10 ***** found room for width:8 at offset: 12 ***** ----------------------------------- *** fit within left of msb test *** ----------------------------------- val1: 00000000000000000000000001000000 ( 64 ) val2: 00010000000000001000010001000001 ( 268469313 ) msb: 6 offbit:0 + width: 13 = 13 mask: 11111111111110000000000000000000 ( 4294443008 ) b: 00010000000000000000000000000000 ( 268435456 ) offbit:4 + width: 13 = 17 mask: 00001111111111111000000000000000 ( 268402688 ) b: 00000000000000001000000000000000 ( 32768 ) ***** mask: 00001111111111111000000000000000 ( 268402688 ) offbit:17 iters:15 ***** no room found for width:13 ***** (iters is the count of iterations of the inner while loop)

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  • Why toInteger :: Int -> Integer is lazy?

    - by joppux
    I have the following code: {-# NOINLINE i2i #-} i2i :: Int -> Integer i2i x = toInteger x main = print $ i2i 2 Running GHC with -ddump-simpl flag gives: [Arity 1 NoCafRefs Str: DmdType U(L)] Main.i2i = GHC.Real.toInteger1 Seems that conversion from Int to Integer is lazy. Why is it so - is there a case when I can have (toInteger _|_ ::Int) /= _|_ ?

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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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  • Updating an integer defined column in a MySQL DB with PHP

    - by Zloy Smiertniy
    I have a table defined like this: create table users ( id int(10), age int(3), name varchar (50) ) I want to use a query to update just age, which is an integer, that comes from an html form. When it arrives to the method that updates it, it comes as a string, so I change it to integer with PHP and try to update the table, but it doesn't work $age = intval($age); $q2 = "UPDATE users SET age='$age' where username like '$username';"; mysql_query($q2,$con);

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  • new Integer vs valueOf

    - by LB
    Hi, I was using Sonar to make my code cleaner, and it pointed that I'm using new Integer(1) instead of Integer.valueOf(1). Because it seems that valueOf does not instantiate a new object so is more memory-friendly. How can valueOf not instantiate a new object ? How does it work ? Is this true for all integers ? thanks.

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  • [C++] Converting Integer to a Byte Representation

    - by bobber205
    How can I convert a integer to it's byte representation. I want to take an integer and return a vector that has contains 1's and 0's of the integers byte representation. I'm having a heck of a time trying to do this myself so I'd thought I would ask to see if there was a built in library function that could help. Thanks!

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  • ON DELETE RESTRICT Causing Error 150

    - by Levi Hackwith
    CREATE TABLE project ( id INTEGER NOT NULL AUTO_INCREMENT, created_at DATETIME NOT NULL, name VARCHAR(75) NOT NULL, description LONGTEXT NOT NULL, is_active TINYINT NOT NULL DEFAULT '1', PRIMARY KEY (id), INDEX(name, created_at) ) ENGINE = INNODB; CREATE TABLE role ( id INTEGER NOT NULL, name VARCHAR(50) NOT NULL, description LONGTEXT NOT NULL, PRIMARY KEY (id) ) ENGINE = INNODB; CREATE TABLE organization ( id INTEGER NOT NULL AUTO_INCREMENT, created_at DATETIME NOT NULL, name VARCHAR(100) NOT NULL, is_active TINYINT NOT NULL DEFAULT '1', PRIMARY KEY (id) ) ENGINE = INNODB; CREATE TABLE user ( id INTEGER NOT NULL AUTO_INCREMENT, created_at DATETIME NOT NULL, role_id INTEGER NOT NULL, organization_id INTEGER NOT NULL, last_login_at DATETIME NOT NULL, last_ip_address VARCHAR(25) NOT NULL, username VARCHAR(45) NOT NULL, password CHAR(32) NOT NULL, email_address VARCHAR(255) NOT NULL, first_name VARCHAR(45) NOT NULL, last_name VARCHAR(45) NOT NULL, address_1 VARCHAR(100) NOT NULL, address_2 VARCHAR(25) NULL, city VARCHAR(25) NOT NULL, state CHAR(2) NOT NULL, zip_code VARCHAR(10) NOT NULL, primary_phone_number VARCHAR(10) NOT NULL, secondary_phone_number VARCHAR(10) NOT NULL, is_primary_organization_contact TINYINT NOT NULL DEFAULT '0', is_active TINYINT NOT NULL DEFAULT '1', PRIMARY KEY (id), CONSTRAINT fk_user_role_id FOREIGN KEY (role_id) REFERENCES role (id) ON UPDATE RESTRICT ON DELETE RESTRICT, CONSTRAINT fk_user_organization_id FOREIGN KEY (organization_id) REFERENCES organization (id) ON UPDATE RESTRICT ON DELETE RESTRICT ) ENGINE = INNODB; CREATE TABLE project_user ( user_id INTEGER NOT NULL, project_id INTEGER NOT NULL, PRIMARY KEY (user_id, project_id), CONSTRAINT fk_project_user_user_id FOREIGN KEY (user_id) REFERENCES user (id) ON UPDATE RESTRICT ON DELETE CASCADE, CONSTRAINT fk_project_user_project_id FOREIGN KEY (project_id) REFERENCES project (id) ON UPDATE RESTRICT ON DELETE RESTRICT ) ENGINE = INNODB; CREATE TABLE ticket_category ( id INTEGER NOT NULL AUTO_INCREMENT, name VARCHAR(20) NOT NULL, description LONGTEXT NOT NULL, PRIMARY KEY (id) ) ENGINE = INNODB; CREATE TABLE ticket_type ( id INTEGER NOT NULL AUTO_INCREMENT, name VARCHAR(20) NOT NULL, description LONGTEXT NOT NULL, PRIMARY KEY (id) ) ENGINE = INNODB; CREATE TABLE ticket_status ( id INTEGER NOT NULL AUTO_INCREMENT, name VARCHAR(20) NOT NULL, description LONGTEXT NOT NULL, PRIMARY KEY (id) ) ENGINE = INNODB; CREATE TABLE ticket ( id INTEGER NOT NULL AUTO_INCREMENT, created_at DATETIME NOT NULL, project_id INTEGER NOT NULL, created_by INTEGER NOT NULL, submitted_by INTEGER NOT NULL, assigned_to INTEGER NULL, category_id INTEGER NOT NULL, type_id INTEGER NOT NULL, title VARCHAR(75) NOT NULL, description LONGTEXT NOT NULL, contact_type_id TINYINT NOT NULL, affects_all_clients TINYINT NOT NULL DEFAULT '0', is_billable TINYINT NOT NULL DEFAULT '1', esimated_hours DECIMAL(4, 1) NOT NULL DEFAULT '0', hours_worked DECIMAL (4, 1) NOT NULL DEFAULT '0', status_id TINYINT NOT NULL, PRIMARY KEY (id), CONSTRAINT fk_ticket_project_id FOREIGN KEY (project_id) REFERENCES project (id) ON UPDATE RESTRICT ON DELETE RESTRICT, CONSTRAINT fk_ticket_created_by FOREIGN KEY (created_by) REFERENCES user (id) ON UPDATE RESTRICT ON DELETE RESTRICT, CONSTRAINT fk_ticket_submitted_by FOREIGN KEY (submitted_by) REFERENCES user (id) ON UPDATE RESTRICT ON DELETE RESTRICT, CONSTRAINT fk_ticket_assigned_to FOREIGN KEY (assigned_to) REFERENCES user (id) ON UPDATE RESTRICT ON DELETE RESTRICT, CONSTRAINT fk_ticket_category_id FOREIGN KEY (category_id) REFERENCES ticket_category (id) ON UPDATE RESTRICT ON DELETE RESTRICT, CONSTRAINT fk_ticket_type_id FOREIGN KEY (type_id) REFERENCES ticket_type (id) ON UPDATE RESTRICT ON DELETE RESTRICT, CONSTRAINT fk_ticket_status_id FOREIGN KEY (status_id) REFERENCES ticket_status (id) ON UPDATE RESTRICT ON DELETE RESTRICT ) ENGINE = INNODB; CREATE TABLE ticket_time_entry ( id INTEGER NOT NULL AUTO_INCREMENT, user_id INTEGER NOT NULL, ticket_id INTEGER NOT NULL, started_at DATETIME NOT NULL, ended_at DATETIME NOT NULL, PRIMARY KEY (id), CONSTRAINT fk_ticket_time_entry_user_id FOREIGN KEY (user_id) REFERENCES user (id) ON UPDATE RESTRICT ON DELETE RESTRICT, CONSTRAINT fk_ticket_time_entry_ticket_id FOREIGN KEY (ticket_id) REFERENCES ticket (id) ON UPDATE RESTRICT ON DELETE RESTRICT ) ENGINE = INNODB; The ticket table's create statement causes an error 150. I have no clue why. When I remove the ON DELETE RESTRICT statements from the table declaration, it works. Why is that?

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  • How Does Modulus Divison Work

    - by NSWOA
    I don't really understand how modulus division works. I was calculating 27 % 16 and wound up with 11 and I don't understand why. I can't seem to find an explanation in layman's terms online. Can someone elaborate on a very high level as to what's going on here? EDIT: Thanks for all your answers. You guys are incredibly quick. It all makes sense now.

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