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  • memory alignment issues with union

    - by confucius
    Hi all, Is there guarantee, that memory for this object will be properly aligned if we create this object of this type in stack? union my_union { int value; char bytes[4]; }; If we create char bytes[4] in stack and then try to cast it to integer there might be alignment problem. We can avoid that problem by creating it in heap, however, is there such guarantee for union objects? Logically there should be, but I would like to confirm. Thanks.

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  • What is the difference between a 32-bit and 64-bit processor?

    - by JJG
    I have been trying to read up on 32-bit and 64-bit processors (http://en.wikipedia.org/wiki/32-bit_processing). My understanding is that a 32-bit processor (like x86) has registers 32-bits wide. I'm not sure what that means. So it has special "memory spaces" that can store integer values up to 2^32? I don't want to sound stupid, but I have no idea about processors. I'm assuming 64-bits is, in general, better than 32-bits. Although my computer now (one year old, Win 7, Intel Atom) has a 32-bit processor.

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  • Delphi Performance: Case Versus If

    - by Andreas Rejbrand
    I guess there might be some overlapping with previous SO questions, but I could not find a Delphi-specific question on this topic. Suppose that you want to check if an unsigned 32-bit integer variable "MyAction" is equal to any of the constants ACTION1, ACTION2, ... ACTIONn, where n is - say 1000. I guess that, besides being more elegant, case MyAction of ACTION1: {code}; ACTION2: {code}; ... ACTIONn: {code}; end; if much faster than if MyAction = ACTION1 then // code else if MyAction = ACTION2 then // code ... else if MyAction = ACTIONn then // code; I guess that the if variant takes time O(n) to complete (i.e. to find the right action) if the right action ACTIONi has a high value of i, whereas the case variant takes a lot less time (O(1)?). Am I correct that switch is much faster? Am I correct that the time required to find the right action in the switch case actually is independent of n? I.e. is it true that it does not really take any longer to check a million cases than to check 10 cases? How, exactly, does this work?

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  • Add two 32-bit integers in Assembler for use in VB6

    - by Emtucifor
    I would like to come up with the byte code in assembler (assembly?) for Windows machines to add two 32-bit longs and throw away the carry bit. I realize the "Windows machines" part is a little vague, but I'm assuming that the bytes for ADD are pretty much the same in all modern Intel instruction sets. I'm just trying to abuse VB a little and make some things faster. So... if the string "8A4C240833C0F6C1E075068B442404D3E0C20800" is the assembly code for SHL that can be "injected" into a VB6 program for a fast SHL operation expecting two Long parameters (we're ignoring here that 32-bit longs in VB6 are signed, just pretend they are unsigned), what is the hex string of bytes representing assembler instructions that will do the same thing to return the sum? The hex code above for SHL is, according to the author: mov eax, [esp+4] mov cl, [esp+8] shl eax, cl ret 8 I spit those bytes into a file and tried unassembling them in a windows command prompt using the old debug utility, but I figured out it's not working with the newer instruction set because it didn't like EAX when I tried assembling something but it was happy with AX. I know from comments in the source code that SHL EAX, CL is D3E0, but I don't have any reference to know what the bytes are for instruction ADD EAX, CL or I'd try it. I tried flat assembler and am not getting anything I can figure out how to use. I used it to assemble the original SHL code and got a very different result, not the same bytes. Help?

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  • RSA_sign and RSACryptoProvider.VerifySignature

    - by Miky D
    I'm trying to get up to speed on how to get some code that uses OpenSSL for cryptography, to play nice with another program that I'm writing in C#, using the Microsoft cryptography providers available in .NET. More to the point, I'm trying to have the C# program verify an RSA message signature generated by the OpenSSL code. The code that generates the signature looks something like this: // Code in C, using the OpenSSL RSA implementation char msgToSign[] = "Hello World"; // the message to be signed char signature[RSA_size(rsa)]; // buffer that will hold signature int slen = 0; // will contain signature size // rsa is an OpenSSL RSA context, that's loaded with the public/private key pair memset(signature, 0, sizeof(signature)); RSA_sign(NID_sha1 , (unsigned char*)msgToSign , strlen(msgToSign) , signature , &slen , rsa); // now signature contains the message signature // and can be verified using the RSA_verify counterpart // .. I would like to verify the signature in C# In C#, I would do the following: import the other side's public key into an RSACryptoServiceProvider object receive the message and it's signature try to verify the signature I've got the first two parts working (I've verified that the public key is loading properly because I managed to send an RSA encrypted text from the C# code to the OpenSSL code in C and successfully have it decrypted) In order to verify the signature in C#, I've tried using the: VerifySignature method of the RSACryptoServiceProvider but that didn't work. And digging around the internet I was only able to find some vague information pointing out that .NET uses a different method for generating the signature than OpenSSL does. So, does anybody know how to accomplish this?

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  • Rails and MongoDB with MongoMapper

    - by FCastellanos
    I'm new to Rails development and I'm starting with MongoDB also. I have been following this Railscast tutorial about complex forms with Rails but I'm using MongoDB as my database. I'm having no problems inserting documents with it's childs and retrieving the data to the edit form, but when I try to update it I get this error undefined method `assert_valid_keys' for false:FalseClass this is my entity class class Project include MongoMapper::Document key :name, String, :required => true key :priority, Integer many :tasks after_update :save_tasks def task_attributes=(task_attributes) task_attributes.each do |attributes| if attributes[:id].blank? tasks.build(attributes) else task = tasks.detect { |t| t.id.to_s == attributes[:id].to_s } task.attributes = attributes end end end def save_tasks tasks.each do |t| t.save(false) end end end Does anyone knows whats happening here? Thanks

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  • What's the reason both Image and Bitmap classes don't implement a custom equality/hashcode logic?

    - by devoured elysium
    From MSDN documentation, it seems as both GetHashCode() and Equals() haven't been overriden in Bitmap. Neither have them been overriden in Image. So both classes are using the Object's version of them just compares references. I wasn't too convinced so I decided to fire up Reflector to check it out. It seems MSDN is correct in that matter. So, is there any special reason why MS guys wouldn't implement "comparison logic", at least for the Bitmap class? I find it is kinda acceptable for Image, as it is an abstract class, but not so much for the Bitmap class. I can see in a lot of situations calculating the hash code can be an expensive operation, but it'd be alright if it used some kind of lazy evaluation (storing the computed hash code integer in a variable a variable, so it wouldn't have to calculate it later again). When wanting to compare 2 bitmaps, will I have to resort to having to run all over the picture comparing each one of its pixels? Thanks

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  • MySQL FULLTEXT aggravation

    - by southof40
    Hi - I'm having problems with case-sensitivity in MySQL FULLTEXT searches. I've just followed the FULLTEXT example in the MySQL doco at http://dev.mysql.com/doc/refman/5.1/en/fulltext-boolean.html . I'll post it here for ease of reference ... CREATE TABLE articles ( id INT UNSIGNED AUTO_INCREMENT NOT NULL PRIMARY KEY, title VARCHAR(200), body TEXT, FULLTEXT (title,body) ); INSERT INTO articles (title,body) VALUES ('MySQL Tutorial','DBMS stands for DataBase ...'), ('How To Use MySQL Well','After you went through a ...'), ('Optimizing MySQL','In this tutorial we will show ...'), ('1001 MySQL Tricks','1. Never run mysqld as root. 2. ...'), ('MySQL vs. YourSQL','In the following database comparison ...'), ('MySQL Security','When configured properly, MySQL ...'); SELECT * FROM articles WHERE MATCH (title,body) AGAINST ('database' IN NATURAL LANGUAGE MODE); ... my problem is that the example shows that SELECT returning the first and fifth rows ('..DataBase..' and '..database..') but I only get one row ('database') ! The example doesn't demonstrate what collation the table in the example had but I have ended up with latin1_general_cs on the title and body columns of my example table. My version of MySQL is 5.1.39-log and the connection collation is utf8_unicode_ci . I'd be really grateful is someone could suggest why my experience differs from the example in the manual ! Be grateful for any advice.

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  • Interesting interview question. .Net

    - by rahul
    Coding Problem NumTrans There is an integer K. You are allowed to add to K any of its divisors not equal to 1and K. The same operation can be applied to the resulting number and so on. Notice that starting from the number 4, we can reach any composite number by applying several such operations. For example, the number 24 can be reached starting from 4 using 5 operations: 468121824 You will solve a more general problem. Given integers n and m, return the minimal number of the described operations necessary to transform n into m. Return -1 if m can't be obtained from n. Definition Method signature: int GetLeastCount (int n, int m) Constraints N will be between 4 and 100000, inclusive. M will be between N and 100000, inclusive. Examples 1) 4 576 Returns: 14 The shortest order of operations is: 468121827365481108162243324432576 2) 8748 83462 Returns: 10 The shortest order of operations is: 874813122196832624439366590497873283106834488346083462 3) 4 99991 Returns: -1 The number 99991 can't be obtained because it’s prime!

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  • Unable to call WMP's controls.play() function in VisualBasic

    - by A.J.
    I have the following code: http://pastebin.com/EgjbzqA2 which is basically just a stripped down version of http://www.dreamincode.net/forums/topic/57357-mymusic-player/. I want the program to play one file repeatedly, however, this function doesn't work for some reason. The program plays each file once and then stops. Private Sub Player3_PlayStateChange(ByVal NewState As Integer) Handles Player3.PlayStateChange Static Dim PlayAllowed As Boolean = True Select Case CType(NewState, WMPLib.WMPPlayState) Case WMPLib.WMPPlayState.wmppsReady If PlayAllowed Then Player3.controls.play() End If Case WMPLib.WMPPlayState.wmppsMediaEnded ' Start protection (without it next wouldn't play PlayAllowed = False ' Play track Player3.controls.play() ' End Protection PlayAllowed = True updatePlayer() End Select End Sub

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  • Is there any way to put extras to Intent from preferences ?

    - by Alex Volovoy
    Hi i'm launching activity from preferences screen. Activity is shared among three preferences. I wonder if i can set extras for this activity in xml <Preference android:key="action_1" android:title="@string/action_1_title" > <intent android:action="com.package.SHAREDACTION" > </intent> </Preference> i wonder if i can do something like <extras> <item android:name="" android:value=""/> </extras> All i need to do to pass an integer really. I can different actions and check action instead of extras.

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  • Where to start on creating finger swipe navigation trough a list.

    - by Thomas Stock
    Lets say I want to make a control to select any integer number by dragging on a "bar" with numbers: (156 is selected) Mousedown on "159" and dragging towards the left and then doing mouseup changes the control to this: (160 is selected) I've been experimenting for the past 3 hours but I'm inexperienced in Silverlight so I'm having problems getting started. My current guess is I should seperate this into 2 steps: Step 1: Build this control without swiping behavior. Just 2 buttons to go up a number or go down a number Step 2: Replace the buttons by handling mouse events. With my limited knowledge I think I would manage building a crappy control that does this, with very messy xaml and c# and lots of headaches when trying to apply styling and fancy state transitions, but I was hoping some xaml wizards could get me started with the basic approach? Edit: This is an implementation of what I'm trying to achieve in Silverlight: Iphone's datepicker:

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  • Is there a simpler way to convert a byte array to a 2-byte-size hexadecimal string?

    - by Tom Brito
    Is there a simpler way of implement this? Or a implemented method in JDK or other lib? /** * Convert a byte array to 2-byte-size hexadecimal String. */ public static String to2DigitsHex(byte[] bytes) { String hexData = ""; for (int i = 0; i < bytes.length; i++) { int intV = bytes[i] & 0xFF; // positive int String hexV = Integer.toHexString(intV); if (hexV.length() < 2) { hexV = "0" + hexV; } hexData += hexV; } return hexData; } public static void main(String[] args) { System.out.println(to2DigitsHex(new byte[] {8, 10, 12})); } the output is: "08 0A 0C" (without the spaces)

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  • MySQL indexes: how do they work?

    - by bob-the-destroyer
    I'm a complete newbie with MySQL indexes. I have several MyISAM tables on MySQL 5.0x having utf8 charsets and collations with 100k+ records each. The primary keys are generally integer. Many columns on each table may have duplicate values. I need to quickly count, sum, average, or otherwise perform custom calculations on any number of fields in each table or joined on any number of others. I found this page giving an overview of MySQL index usage: http://dev.mysql.com/doc/refman/5.0/en/mysql-indexes.html, but I'm still not sure I'm using indexes right. Just when I think I've made the perfect index out of a collection of fields I want to calculate against, I get the "index must be under 1000 bytes" error. Can anyone explain how to most efficiently create and use indexes to speed up queries? Caveat: upgrading Mysql is not possible in this case. Using Navicat Light for db administration, but this app isn't required.

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  • Traverse list to add elements using .NET

    - by Addie
    I have a list of objects. Each object has an integer quantity and a DateTime variable which contains a month and year value. I'd like to traverse the list and pad the list by adding missing months (with quantity 0) so that all consecutive months are represented in the list. What would be the best way to accomplish this? Example: Original List { Jan10, 3 }, { Feb10, 4 }, { Apr10, 2 }, { May10, 2 }, { Aug10, 3 }, { Sep10, -3 }, { Oct10, 6 }, { Nov10, 3 }, { Dec10, 7 }, { Feb11, 3 } New List { Jan10, 3 }, { Feb10, 4 }, {Mar10, 0}, { Apr10, 2 }, { May10, 2 }, { Jun10, 0 }, { Jul10, 0 } { Aug10, 3 }, { Sep10, -3 }, { Oct10, 6 }, { Nov10, 3 }, { Dec10, 7 }, { Jan11, 0 }, { Feb11, 3 }

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  • Attaching HTML file as email in VB 6.0

    - by Shax
    Hi, I am trying to attach an html file file to email using Visual Basic 6.0. when the cursor is comes on Open strFile For Binary Access Read As #hFile line it gives error "Error encoding file - Bad file name or number". Please all your help and support would be highly appreciated. Dim handleFile As Integer Dim strValue As String Dim lEventCtr As Long handleFile = FreeFile Open strFile For Binary Access Read As #handleFile Do While Not EOF(hFile) ' read & Base 64 encode a line of characters strValue = Input(57, #handleFile) SendCommand EncodeBase64String(strValue) & vbCrLf ' DoEvents (occasionally) lEventCtr = lEventCtr + 1 If lEventCtr Mod 50 = 0 Then DoEvents Loop Close #handleFile Exit Sub File_Error: Close #handleFile m_ErrorDesc = "Error encoding file - " & Err.Description Err.Raise Err.Number, Err.Source, m_ErrorDesc End Sub

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  • c# control location precision

    - by AC
    I need more precision then integer based locations when puttng controls on a form. It seems control.location only supports Point. Is there a work around for this? Point p = new Point(100, 200); this.Location = p;// this works of course PointF pF = new PointF(100.04f, 200.08f); this.Location = pF;// this does not work of course because Location expects a Point not PointF Is there some setting on the base form, or base control I can set to have more location precision?

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  • I can't figure out why this fps counter is inaccurate.

    - by rmetzger
    I'm trying to track frames per second in my game. I don't want the fps to show as an average. I want to see how the frame rate is affected when I push keys and add models etc. So I am using a variable to store the current time and previous time, and when they differ by 1 second, then I update the fps. My problem is that it is showing around 33fps but when I move the mouse around really fast, the fps jumps up to 49fps. Other times, if I change a simple line of code elsewhere not related to the frame counter, or close the project and open it later, the fps will be around 60. Vsync is on so I can't tell if the mouse is still effecting the fps. Here is my code which is in an update function that happens every frame: FrameCount++; currentTime = timeGetTime (); static unsigned long prevTime = currentTime; TimeDelta = (currentTime - prevTime) / 1000; if (TimeDelta > 1.0f) { fps = FrameCount / TimeDelta; prevTime = currentTime; FrameCount = 0; TimeDelta = 0; } Here are the variable declarations: int FrameCount; double fps, currentTime, prevTime, TimeDelta, TimeElapsed; Please let me know what is wrong here and how to fix it, or if you have a better way to count fps. Thanks!!!!!! I am using DirectX 9 btw but I doubt that is relevant, and I am using PeekMessage. Should I be using an if else statement instead? Here is my message processing loop: MSG msg; ZeroMemory (&msg, sizeof (MSG)); while (msg.message != WM_QUIT) { if (PeekMessage(&msg, NULL, 0, 0, PM_REMOVE)) { TranslateMessage (&msg); DispatchMessage (&msg); } Update (); RenderFrame (); }

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  • recommended format to save time with MJD + BCD format in database

    - by pierr
    Hi, There is a time represented in MJD and BCD format with 5 bytes .I am wondering what is the recommended format to save this date-time in the sqlite database so that user can search against it ? My first attempt is to save it just as it is, that is a 5 bytes string. The user will use the same format to search and the result will be converted to unix time by the user with following code. However, later, I was suggested to save the time in the integer - the UTC time, for example. But I can not find a standard way to do the conversion. I feel this is a common issue and would like to hear your comments. time_t sidate_to_unixtime(unsigned char sidate[]) { int k = 0; struct tm tm; double mjd; /* check for the undefined value */ if ((sidate[0] == 0xff) && (sidate[1] == 0xff) && (sidate[2] == 0xff) && (sidate[3] == 0xff) && (sidate[4] == 0xff)) { return -1; } memset(&tm, 0, sizeof(tm)); mjd = (sidate[0] << 8) | sidate[1]; tm.tm_year = (int) ((mjd - 15078.2) / 365.25); tm.tm_mon = (int) (((mjd - 14956.1) - (int) (tm.tm_year * 365.25)) / 30.6001); tm.tm_mday = (int) mjd - 14956 - (int) (tm.tm_year * 365.25) - (int) (tm.tm_mon * 30.6001); if ((tm.tm_mon == 14) || (tm.tm_mon == 15)) k = 1; tm.tm_year += k; tm.tm_mon = tm.tm_mon - 2 - k * 12; tm.tm_sec = bcd_to_integer(sidate[4]); tm.tm_min = bcd_to_integer(sidate[3]); tm.tm_hour = bcd_to_integer(sidate[2]); return mktime(&tm); }

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  • SQLAlchemy - how to map against a read-only (or calculated) property

    - by Jeff Peck
    I'm trying to figure out how to map against a simple read-only property and have that property fire when I save to the database. A contrived example should make this more clear. First, a simple table: meta = MetaData() foo_table = Table('foo', meta, Column('id', String(3), primary_key=True), Column('description', String(64), nullable=False), Column('calculated_value', Integer, nullable=False), ) What I want to do is set up a class with a read-only property that will insert into the calculated_value column for me when I call session.commit()... import datetime def Foo(object): def __init__(self, id, description): self.id = id self.description = description @property def calculated_value(self): self._calculated_value = datetime.datetime.now().second + 10 return self._calculated_value According to the sqlalchemy docs, I think I am supposed to map this like so: mapper(Foo, foo_table, properties = { 'calculated_value' : synonym('_calculated_value', map_column=True) }) The problem with this is that _calculated_value is None until you access the calculated_value property. It appears that SQLAlchemy is not calling the property on insertion into the database, so I'm getting a None value instead. What is the correct way to map this so that the result of the "calculated_value" property is inserted into the foo table's "calculated_value" column?

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  • Python Beginner: Selective Printing in loops

    - by Jonathan Straus
    Hi there. I'm a very new python user (had only a little prior experience with html/javascript as far as programming goes), and was trying to find some ways to output only intermittent numbers in my loop for a basic bicycle racing simulation (10,000 lines of biker positions would be pretty excessive :P). I tried in this loop several 'reasonable' ways to communicate a condition where a floating point number equals its integer floor (int, floor division) to print out every 100 iterations or so: for i in range (0,10000): i = i + 1 t = t + t_step #t is initialized at 0 while t_step is set at .01 acceleration_rider1 = (power_rider1 / (70 * velocity_rider1)) - (force_drag1 / 70) velocity_rider1 = velocity_rider1 + (acceleration_rider1 * t_step) position_rider1 = position_rider1 + (velocity_rider1 * t_step) force_drag1 = area_rider1 * (velocity_rider1 ** 2) acceleration_rider2 = (power_rider2 / (70 * velocity_rider1)) - (force_drag2 / 70) velocity_rider2 = velocity_rider2 + (acceleration_rider2 * t_step) position_rider2 = position_rider2 + (velocity_rider2 * t_step) force_drag2 = area_rider1 * (velocity_rider2 ** 2) if t == int(t): #TRIED t == t // 1 AND OTHER VARIANTS THAT DON'T WORK HERE:( print t, "biker 1", position_rider1, "m", "\t", "biker 2", position_rider2, "m"

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  • [C++]Advantage of using a static member function instead of an equivalent non-static member function

    - by jonathanasdf
    I was wondering whether there's any advantages to using a static member function when there is a non-static equivalent. Will it result in faster execution (because of not having to care about all of the member variables), or maybe less use of memory (because of not being included in all instances)? Basically, the function I'm looking at is an utility function to rotate an integer array representing pixel colours an arbitrary number of degrees around an arbitrary centre point. It is placed in my abstract Bullet base class, since only the bullets will be using it and I didn't want the overhead of calling it in some utility class. It's a bit too long and used in every single derived bullet class, making it probably not a good idea to inline. How would you suggest I define this function? As a static member function of Bullet, of a non-static member function of Bullet, or maybe not as a member of Bullet but defined outside of the class in Bullet.h? What are the advantages and disadvantages of each?

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  • Resolving type parameter values passed to ancester type using reflection

    - by Tom Tucker
    I've asked a similar question before, but this one is much more challenging. How do I find a value of a specific type parameter that is passed to an ancestor class or an interface implemented by one of its ancestor classes using reflection? I basically need to write a method that looks like this. // Return the value of the type parameter at the index passed to the parameterizedClass from the clazz. Object getParameterValue(Class<?> clazz, Class<?> parameterizedClass, int index) For the example below, getParameterValue(MyClass.class, Map.class, 1) would return String.class public class Foo<K, V> implements Map<K, V>{ } public class Bar<V> extends Foo<Integer, V> { } public class MyClass extends Bar<String> { } Thanks!

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  • Memory Management - Objective C NSString

    - by reising1
    I have an NSMutableDictionary called "output" and I am adding an NSString into it that is an integer. What is the proper way to do this? I can't figure it out. Everything I've tried ends up giving memory leaks. This is what I currently have: val is an int countryName is an NSString Here is how I declare "output": NSMutableDictionary *output = [[[NSMutableDictionary alloc] init] autorelease]; Here is the code that causes a memory leak: NSString *temp = [NSString stringWithFormat:@"%d",val]; [output setValue:temp forKey:countryName];

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  • Code Golf: Phone Number to Words

    - by Nick Hodges
    Guidelines for code-golf on SO We've all seen phone numbers that are put into words: 1-800-BUY-MORE, etc. What is the shortest amount of code you can write that will produce all the possible combinations of words for a 7 digit US phone number. Input will be a seven digit integer (or string, if that is simpler), and assume that the input is properly formed. Output will be a list of seven character strings that For instance, the number 428-5246 would produce GATJAGM GATJAGN GATJAGO GATJAHM GATJAHN GATJAHO and so on..... Winning criteria will be code from any language with the fewest characters that produce every possible letter combination. Additional Notes: To make it more interesting, words can be formed only by using the letters on a North American Classic Key Pad phone with three letters per number as defined here.That means that Z and Q are excluded. For the number '1', put a space. For the number '0', put a hyphen '-' Bonus points awarded for recognizing output as real English words. Okay, not really. ;-)

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