Re: Modulo Function [modified] - C# Discussion Boards

Re: Modulo Function

harold aptroot28-Aug-09 5:36

harold aptroot

28-Aug-09 5:36

Quake2Player wrote:

But C# (and java I think) return -10

Could you show the code? That really isn't what should happen, not in Java either.

Re: Modulo Function

Dave Kreskowiak28-Aug-09 7:15

Dave Kreskowiak

28-Aug-09 7:15

Your code is bad somewhere. For two positive integers, modulo is never negative.

A guide to posting questions on CodeProject[^]

Dave Kreskowiak
Microsoft MVP
Visual Developer - Visual Basic
2006, 2007, 2008
But no longer in 2009...

Re: Modulo Function

Quake2Player28-Aug-09 7:22

Quake2Player

28-Aug-09 7:22

Random r = new Random();

int key = r.Next(0, 10000);
int prime = r.Next(key, key * 999);
int a = r.Next(1, prime - 1);
int b = r.Next(0, prime - 1);

Console.WriteLine(key);
Console.WriteLine(prime);
Console.WriteLine(a);
Console.WriteLine(b);

Console.WriteLine( ((key*a + b)%prime) % 1000);
Console.ReadLine();

For example:
In google: (((8 568 * 4 974 445) + 2 820 002) % 7 661 773) % 1 000 = 563}
In c#: (((8 568 * 4 974 445) + 2 820 002) % 7 661 773) % 1 000 = -732

Re: Modulo Function

Luc Pattyn28-Aug-09 7:38

Luc Pattyn

28-Aug-09 7:38

Quake2Player wrote:
8 568 * 4 974 445)

using 32-bit signed arithmetic (as in int) this results in an overflow, that is where the negative stuff is coming from. Nothing wrong with the modulo operator.

test: declare long variables, initialize them, and use those for your expression, instead of numeric constants. (decimal should work too).

Smile | :)

Luc Pattyn

Badger | [badger,badger,badger,badger...]

Have a look at my entry for the lean-and-mean competition; please provide comments, feedback, discussion, and don’t forget to vote for it! Thank you.

Re: Modulo Function

DaveyM6928-Aug-09 7:38

DaveyM69

28-Aug-09 7:38

Beat me to it! Mad | :mad:

Dave
BTW, in software, hope and pray is not a viable strategy. (Luc Pattyn)
Visual Basic is not used by normal people so we're not covering it here. (Uncyclopedia)
Why are you using VB6? Do you hate yourself? (Christian Graus)

Re: Modulo Function

Quake2Player28-Aug-09 14:46

Quake2Player

28-Aug-09 14:46

THANK YOU!

Re: Modulo Function

DaveyM6928-Aug-09 7:38

DaveyM69

28-Aug-09 7:38

It's because of the overflow in the first part of the calculation. Make one of the values a double and you get the correct result.
(((8568 * 4974445d) + 2820002) % 7661773) % 1000)

Re: Modulo Function [modified]

Quake2Player29-Aug-09 11:55

Quake2Player

29-Aug-09 11:55

How can I use long if I'm generating random numbers???

This is all about the UNIVERSAL HASHING FUNCTION:

<code>
        public int Evaluate(int key) 
        {
                // Random prime bigger than 10000
                do {
                  randomPrime = rnd.Next(10001, 10000*999);
                }
                while (!IsPrime(randomPrime));

                this.randomA = rnd.Next(1, randomPrime - 1);
                this.randomB = rnd.Next(0, randomPrime - 1);

                return ((randomA * key + randomB) % randomPrime) % tableLength;
        }
</code>

Notes:
-10000 is the maximum possible key
-tableLength is 1000.
-randomA, randomB and randomPrime are ints

As Im getting negative numbers Im trying
return Math.Abs(((randomA * key + randomB) % randomPrime) % tableLength);

But its not giving me fast results in the hash table

modified on Saturday, August 29, 2009 6:01 PM

Using Text Files

gamer112728-Aug-09 4:54

gamer1127

28-Aug-09 4:54

Hello. I just want to know if its possible for me to store the data inside an array to a text file and also if its possible to transfer all the data in the text file into an array?

Re: Using Text Files

Coding C#28-Aug-09 4:55

Coding C#

28-Aug-09 4:55

Yes - Its possible Smile | :)

Coding C#

ExciteTemplate

Re: Using Text Files

gamer112728-Aug-09 5:13

gamer1127

28-Aug-09 5:13

Ok..Thanks.. Wink | ;)

Re: Using Text Files

OriginalGriff28-Aug-09 5:07

OriginalGriff

28-Aug-09 5:07

As Coding says, yes it is possible. How you do it will depend on what kind of info you have in your array, and what you want to do with the text file.

If it is an array of strings, easy peasy.
If it is an array of something else, then slightly harder - you will either have to do the work yourself or use a Formatter - XML, Binary or Soap.

No trees were harmed in the sending of this message; however, a significant number of electrons were slightly inconvenienced.

This message is made of fully recyclable Zeros and Ones

Re: Using Text Files

gamer112728-Aug-09 5:19

gamer1127

28-Aug-09 5:19

oh..ok then..thanks for the info..

Re: Using Text Files

OriginalGriff28-Aug-09 5:34

OriginalGriff

28-Aug-09 5:34

Sorry, that was a little unhelpfull!

For an array of strings, look at File.WriteAllLines[^]. To read it back, use ReadAllLines

For an array of something else, you will need to:
1) Open file
2) Set up a loop through each element of the array
3) For each element, use ToString member, or string.Format to create a string
4) Write the string to the file
5) Close the file.

To read them back, use the Parse method after reading the line.

or look at BinaryFormatter, XMLFormatter and SoapFormatter in the MSDN, but these will not necessarily create a file you want to look at, or edit by hand!

Good luck!

No trees were harmed in the sending of this message; however, a significant number of electrons were slightly inconvenienced.

This message is made of fully recyclable Zeros and Ones

Re: Using Text Files

Luc Pattyn28-Aug-09 7:40

Luc Pattyn

28-Aug-09 7:40

TMI
the first "yes" was the best answer Laugh | :laugh:

Luc Pattyn

Have a look at my entry for the lean-and-mean competition; please provide comments, feedback, discussion, and don’t forget to vote for it! Thank you.

Re: Using Text Files

OriginalGriff28-Aug-09 8:19

OriginalGriff

28-Aug-09 8:19

I thought so - it was an accurate and complete answer - but not so helpful to a beginner! Laugh | :laugh:

That's why I apologised and gave more info.

I'm trying to obey the new rules...but some of these questions do make it difficult.

No trees were harmed in the sending of this message; however, a significant number of electrons were slightly inconvenienced.

This message is made of fully recyclable Zeros and Ones

Change richtextbox colors - C#

OrkanA28-Aug-09 4:39

OrkanA

28-Aug-09 4:39

Hello everyone,

I need help,

How can I change "visited links color" in richtextbox ? - C#
I mean, when I click a link in richtextbox, clicked link opens an ie page.
But clicked link color doesn't change... ( I want to change it's color )

Please help me,

Best Regards.

Re: Change richtextbox colors - C#

OrkanA29-Aug-09 4:57

OrkanA

29-Aug-09 4:57

nobody ??? Frown | :(

is it impossible ?

DataBinding removal error

kanchoette28-Aug-09 4:29

kanchoette

28-Aug-09 4:29

I have a textBox databound to a datatable via the properties window. It works well.
I now need to remove this databinding. When doing this, via the properties window, and setting the Text section of DataBindings back to 'None' I get this error when re-running the solution:

'object reference not set to an instance of an object' for line:

firstPaymentDateTextBox.DataBindings["Text"].Format += new ConvertEventHandler(DebtConvert.DateToString);

it seems that VS 2008 does not remove this line when resetting the databinding via the designer properties window. It there a way around this please? As I have a lot of databindings to remove it seems a little tedious for such a, otherwise, powerful IDE.

Re: DataBinding removal error

Keith Barrow28-Aug-09 4:34

Keith Barrow

28-Aug-09 4:34

Why do you need to remove the bindings?

Re: DataBinding removal error

kanchoette30-Aug-09 4:21

kanchoette

30-Aug-09 4:21

The project has changed and the data binding for the textbox is no longer required.

I need to resize a large image of more than 2MEGABYTE and I can not upload it to the program

gilvani28-Aug-09 3:54

gilvani

28-Aug-09 3:54

I have an image of more than 2 megabytes that can not open in any program,
so I need to resize it so that any program can open if I could carry it in the program would be easy but it has an error OUT OF MEMORY someone tell me how to resize the image without loading in C Sharp

Re: I need to resize a large image of more than 2MEGABYTE and I can not upload it to the program

Luc Pattyn28-Aug-09 4:07

Luc Pattyn

28-Aug-09 4:07

Hi,

an OOM exception does not always really mean you ran out of memory! Look here[^].

I suggest you first validate your image file by opening it succesfully with one of the reputed image processing programs, such as Adobe Photoshop.

Smile | :)

Luc Pattyn

Have a look at my entry for the lean-and-mean competition; please provide comments, feedback, discussion, and don’t forget to vote for it! Thank you.

Re: I need to resize a large image of more than 2MEGABYTE and I can not upload it to the program

OriginalGriff28-Aug-09 5:10

OriginalGriff

28-Aug-09 5:10

I agree with Luc - I regularly work with images much bigger than 2Meg without problems in C#. I would suspect your code is at fault - try it with a small test image, and it will probably give the same error.

No trees were harmed in the sending of this message; however, a significant number of electrons were slightly inconvenienced.

This message is made of fully recyclable Zeros and Ones

Re: I need to resize a large image of more than 2MEGABYTE and I can not upload it to the program

gilvani28-Aug-09 7:02

gilvani

28-Aug-09 7:02

The problem is not in my code is on the image that is a bmp and is a large map and i tried to open the image with Irfanview with Quantum gis and with the Gimp and the Windows can not read the image data. I want to resize the image from the file system and not from the image that appears on the screen.

I have not harmed any tree to write this message but have produced a lot of smoke trying to resize the image.
Thank's

Use Ctrl+Left/Right to switch messages, Ctrl+Up/Down to switch threads, Ctrl+Shift+Left/Right to switch pages.