The IFormattable interface

Implementing the IFormattable interface let's you do much more with the ToString() method if you're developing text-based applications or are trying to create strings out of object fields.

To implement the IFormattable interface, you have to create a ToString method that accepts a format string and an IFormatProvider object. The IFormatProvider object isn't relevant but the format string can be used, such as to return only one field of an object. Here's a sample implementation:

class TimeInterval : IFormattable {

...

public override string ToString() {
return ToString(null, null);
}

public string ToString (string format, IFormatProvider formatProvider) {
if (format == null) {
return this.Hour.ToString() + ":" + this.Minute.ToString();
} else if (format == "h") {
return this.Hour.ToString();
} else if (format == "m") {
return this.Minute.ToString();
} else throw new Exception("Invalid format specified");
}
}

To use the new method, you could provide a format string to either string.Format or Console.WriteLine. Example:
TimeInterval timeInterval = new TimeInterval();
Console.WriteLine("{0:h} hours and {0:m} minutes", timeInterval);
Console.WriteLine("{0,2:h}:{0,2:m}", timeInterval); //the ",2" specifies the minimum number of characters in the resulting string - if positive, the output is left-padded, otherwise it is right-padded

Common Interfaces

The following are some common interfaces implemented by user-defined types:

IComparable: This is required for sorting.

IDisposable: This is used for manually disposing an object

IConvertible: This provides conversion to a base type

ICloneable: This is to provide a copy for an object

IEquatable: This is used when comparison of objects using "==" is required

IFormattable: This is used to convert an object into a formatted string (rather than use the base ToString method)

Group chat coming soon in GoogleTalk

Google has a GoogleTalk gadget web client accessible from it's website at http://www.google.com/talk . It features Group chat but the downside is that it doesn't receive offline messages. As a friend from the old country would say, you've got to pick what suits the moment.

If it's any indicate of what's to come, we should see Group Chat in the GoogleTalk client sometime soon.

RSS vs Atom

RSS and Atom are both used to publish news feeds (summarized content used by readers to track content changes). Both are quite popular, although RSS has received more attention than Atom. RSS is a specification by the Harvard University, whereas Atom is an RFC by the IETF and IESG.

I read a pretty interesting comparison of the two at:
http://www.intertwingly.net/wiki/pie/Rss20AndAtom10Compared

VB 7 vs VB 8: Operator Overloading

When designing .NET as a programming platform, the designers could either leave out operator overloading, as Java does, or they could continue the tradition started off by C and continued by C++ to provide greater control to the programmer. They chose to let the programmer decide which path to take and so added the feature into the framework, but for some reason didn't provide a way to use it through Visual Basic .NET 2003 (VB 7).

In .NET 1.1, VB 7 did not include the concept of operator overloading. You could neither define nor use overloaded operators and the workaround was to create methods, such as a .Add(object) method. C#, however, did include operator overloading even on .NET 1.1.

.NET 2.0 introduced the Operator keyword in Visual Basic, a feature in VB 8, which reduces the amount of code and provides added convenience for the developers.

.NET Value Types

Value types in .NET

The following are the built-in value types in .NET. Value types are stored on the stack and can be accessed more efficiently than reference types.

Type: SByte
Alias(es): sbyte
Size (in bytes): 1
Range: -128 to 127

Type: Byte
Alias(es): byte
Size (in bytes): 1
Range: 0 to 255

Type: Int16
Alias(es): Short, short
Size (in bytes): 2
Range: -32768 to 32767

Type: Int32
Alias(es): Integer, int
Size (in bytes): 4
Range: -2147483648 to 2147483647

Type: UInt32
Alias(es): UInteger, uint
Size (in bytes): 4
Range: 0 to 4294967295

Type: Int64
Alias(es): Long, long
Size (in bytes): 8
Range: -9223372036854775808 to 9223372036854775807

Type: Single
Alias(es): float
Size (in bytes): 4
Range: -3.402823E+38 to 3.402823E+38

Type: Double
Alias(es): double
Size (in bytes): 8
Range: -1.79769313486232E+308 to 1.79769313486232E+308

Type: Decimal
Alias(es): decimal
Size (in bytes): 16
Range: -79228162514264337593543950335 to 79228162514264337593543950335

Type: Char
Alias(es): char
Size (in bytes): 2
Range:

Type: Boolean
Alias(es): bool
Size (in bytes): ?
Range: true, false

Type: IntPtr
Alias(es):
Size (in bytes): Platform-specific
Range:

Type: DateTime
Alias(es): Date, date
Size (in bytes): 8
Range: 1/1/0001 12:00:00 AM to 12/31/9999 11:59:59 PM


Operations with Int32, UInt32 and Double types are optimized by the runtime or the hardware.

Browsing the Linux source code

The Linux source code is a pain to go through. There's so much in there that you need to get someone to tell you where to look if you're ever planning to change anything. There are things to make your life easier, though. The LXR C source code to HTML converter adds cross-references and hyperlinks so you can find your way around just any piece of C source code. The folks at Promethos were nice enough to run the LXR on the Linux source code and the resulting HTML is available at: http://www.promethos.org/lxr/http/source

Unlike in real life, most of the good things in the computing world are free!