Semester Project Help

I'm fairly new to VB and programming in General. BUt I'm trying to finish my semester project and I keep getting stuck.

I have a two dimensional array that i need to write to a text file and then also be able to read that same text file if the program is reopened.

The array has 25 Rows and 9 Columns.

I can convert the input into the array but can't get it written to the file.

Any help would be greatly appreciated.

http://msdn.microsoft.com/en-us/library/system.io.file.aspx

spivonious said:

http://msdn.microsoft.com/en-us/library/system.io.file.aspx

I know how to use StreamWriter/Reader but writing to the file kills the format of the array which I'm trying to maintain in the file itself

YellowLT said:

spivonious said:

*snip*

I know how to use StreamWriter/Reader but writing to the file kills the format of the array which I'm trying to maintain in the file itself

There are probably a billion and a half ways to do this.  Among them, csv format:

http://en.wikipedia.org/wiki/Comma-separated_values

YellowLT said:

spivonious said:

*snip*

I know how to use StreamWriter/Reader but writing to the file kills the format of the array which I'm trying to maintain in the file itself

In C#, because I'm feeling cruel to a VB newbie (though converting it to VB should be easy enough)

public static void Write2DArrayToFile(int[,] data, String fileName) {

    using(FileStream fs = new FileStream(fileName, FileMode.Create, FileAccess.Write) {

        // write out some useful header information

       fs.Write( data.GetUpperBound(0) );

       fs.Write( data.GetUpperBound(1) );

        for(int x=0;x<=data.GetUpperBound(0);x++) {

            for(int y=0;y<=data.GetUpperBound(1);y++) {

                fs.Write( data[x,y] ); // as the data is fixed-size, you don't need to use any seperator characters like commas or tabs

            }

        }

    }

}

and to read:

public static int[] Read2DArrayFromFile(String fileName) {
    
    int[,] ret;
    using(FileStream fs = new FileStream(fileName, FileMode.Open, FileAccess.Read)
    using(BinaryReader rdr = new BinaryReader(fs)) {
        
        int width = rdr.ReadInt32();
        int height = rdr.ReadInt32();
        
        ret = new int[ width, height ];
        
        for(int x=0;x<width;x++) {
            for(int y=0;y<height;y++) {
                
                ret[x,y] = rdr.ReadInt32();
            }  
        }
       

    }
    return ret;
}

If you open the stream in binary you can literally dump the object (array) straight into it. Although I'm not going to tell you how since you should NEVER DO THAT.

The above solution is pretty good, I would use that (flawed assumptions about data size aside ).

ManipUni said:

If you open the stream in binary you can literally dump the object (array) straight into it. Although I'm not going to tell you how since you should NEVER DO THAT.

 

The above solution is pretty good, I would use that (flawed assumptions about data size aside ).

What flawed assumptions? in C# 'int' is always an alias for System.Int32 which will always take up 4 bytes, the same applies to Java. This isn't like C or C++ where 'int' has no strict definition.

W3bbo said:

ManipUni said:

*snip*

What flawed assumptions? in C# 'int' is always an alias for System.Int32 which will always take up 4 bytes, the same applies to Java. This isn't like C or C++ where 'int' has no strict definition.

In C#, yes, in the .Net framework? No...

I'm just saying you could have easily turned them into int32's and then it works in every language across the framework and even if they ever changed the definition of an int (to int64) you would still be safe.

I won't lie, I have spent too much time in C/C++ and my mind is just wired to - "never do that!!!"

ManipUni said:

W3bbo said:

*snip*

In C#, yes, in the .Net framework? No...

I'm just saying you could have easily turned them into int32's and then it works in every language across the framework and even if they ever changed the definition of an int (to int64) you would still be safe.

 

I won't lie, I have spent too much time in C/C++ and my mind is just wired to - "never do that!!!"

Uhm, what? There is no definition of 'int' in the CLS as it's a language keyword. Besides, my code won't work in every language in the framework because of its use of C#-specific constructs like using-blocks and multidimensional arrays. The code I wrote is future-proof and the 'int' keyword will never be remapped to System.Int64.

W3bbo said:

ManipUni said:

*snip*

Uhm, what? There is no definition of 'int' in the CLS as it's a language keyword. Besides, my code won't work in every language in the framework because of its use of C#-specific constructs like using-blocks and multidimensional arrays. The code I wrote is future-proof and the 'int' keyword will never be remapped to System.Int64.

Fine. You win. I shouldn't have brought it up.

Just not my style, I guess...

YellowLT said:

spivonious said:

*snip*

I know how to use StreamWriter/Reader but writing to the file kills the format of the array which I'm trying to maintain in the file itself

csv file. just a few things you need to do and it will work fine.

you write each row of the array as one line of text.

each column gets delimited with a ","

if the array is just ints or other numbers thats it.

if the array is strings then delimit each string with quotes  so it looks like "One","Two",Three"

if numbers and strings combine like this:

1,"alpha",34.5,"Beta"

this is a classic file format for storing and exchanging data.

figuerres said:

YellowLT said:

*snip*

csv file. just a few things you need to do and it will work fine.

 

you write each row of the array as one line of text.

each column gets delimited with a ","

if the array is just ints or other numbers thats it.

if the array is strings then delimit each string with quotes  so it looks like "One","Two",Three"

if numbers and strings combine like this:

1,"alpha",34.5,"Beta"

 

this is a classic file format for storing and exchanging data.

I would always use quotations when writing out to CSV.

Keep in mind numbers can contain commas (in the EU).

ManipUni said:

figuerres said:

*snip*

I would always use quotations when writing out to CSV.

 

Keep in mind numbers can contain commas (in the EU).

I thought we weren't supposed to give answers to students. Isn't that in the rules?

Oh well.

spivonious said:

ManipUni said:

*snip*

I thought we weren't supposed to give answers to students. Isn't that in the rules?

 

Oh well.

Well, they're not giving directly 'cut-and-paste'-able answers, so I think this approach is OK.  Students have got to have some reference resources.

Herbie

Dr Herbie said:

spivonious said:

*snip*

Well, they're not giving directly 'cut-and-paste'-able answers, so I think this approach is OK.  Students have got to have some reference resources.

 

Herbie

 

Indeed.

If nobody ever helped anyone else out with code then I don't think I would be able to code as well as I can... I often google for online references to bits and pieces.

W3bbo said:

YellowLT said:

*snip*

In C#, because I'm feeling cruel to a VB newbie (though converting it to VB should be easy enough)

 

public static void Write2DArrayToFile(int[,] data, String fileName) {

    using(FileStream fs = new FileStream(fileName, FileMode.Create, FileAccess.Write) {

        // write out some useful header information

       fs.Write( data.GetUpperBound(0) );

       fs.Write( data.GetUpperBound(1) );

        for(int x=0;x<=data.GetUpperBound(0);x++) {

            for(int y=0;y<=data.GetUpperBound(1);y++) {

                fs.Write( data[x,y] ); // as the data is fixed-size, you don't need to use any seperator characters like commas or tabs

            }

        }

    }

}

 

and to read:

 

public static int[] Read2DArrayFromFile(String fileName) {
    
    int[,] ret;
    using(FileStream fs = new FileStream(fileName, FileMode.Open, FileAccess.Read)
    using(BinaryReader rdr = new BinaryReader(fs)) {
        
        int width = rdr.ReadInt32();
        int height = rdr.ReadInt32();
        
        ret = new int[ width, height ];
        
        for(int x=0;x<width;x++) {
            for(int y=0;y<height;y++) {
                
                ret[x,y] = rdr.ReadInt32();
            }  
        }
       

    }
    return ret;
}

Or you could do it the lazy way, and just serialize the array. It does all the type checking etc. for you.

Public Sub WriteArray(ByVal data(,) As Integer, ByVal fileName As String)
    If data Is Nothing Then Throw New ArgumentNullException("data")
    If fileName Is Nothing Then Throw New ArgumentNullException("fileName")
    Dim formatter As New BinaryFormatter
    Using stream As FileStream = File.Create(fileName)
        formatter.Serialize(stream, data)
    End Using
End Sub
Public Function ReadArray(ByVal fileName As String) As Integer(,)
    If fileName Is Nothing Then Throw New ArgumentNullException("fileName")
    Dim formatter As New BinaryFormatter
    Using stream As FileStream = File.OpenRead(fileName)
        Return DirectCast(formatter.Deserialize(stream), Integer(,))
    End Using
End Function

Sven Groot said:

W3bbo said:

*snip*

Or you could do it the lazy way, and just serialize the array. It does all the type checking etc. for you.

 

Public Sub WriteArray(ByVal data(,) As Integer, ByVal fileName As String)
    If data Is Nothing Then Throw New ArgumentNullException("data")
    If fileName Is Nothing Then Throw New ArgumentNullException("fileName")
    Dim formatter As New BinaryFormatter
    Using stream As FileStream = File.Create(fileName)
        formatter.Serialize(stream, data)
    End Using
End Sub
Public Function ReadArray(ByVal fileName As String) As Integer(,)
    If fileName Is Nothing Then Throw New ArgumentNullException("fileName")
    Dim formatter As New BinaryFormatter
    Using stream As FileStream = File.OpenRead(fileName)
        Return DirectCast(formatter.Deserialize(stream), Integer(,))
    End Using
End Function

Please remain in your current location, I am sending the code police.

ManipUni said:

Sven Groot said:

*snip*

Please remain in your current location, I am sending the code police.

You do realize that BinaryFormatter is not just a dump of the in-memory datastructure, right? Sure, I wouldn't actually do this in production code, but it's not as terrible as it seems at first glance.