Part 6
Some properties of an Empty String

Strings can also be empty. An empty String is a unique string of length zero.   

Empty string is denoted by a Greek symbol Λ (lambda).  If we have an empty string α then we can write: α =  Λ, or α =  empty_string.

Using formal language we can also describe the properties of an empty string:

1. The length of an empty string is zero:

         |Λ| = 0;

 2. Any non-empty string concatenated with an empty string produces the same non-empty string:

x, y :T and β = <x>  then 
Λ  o  β = β; and <y> o Λ = <y>;

3. The length of any non-empty string concatenated with an empty string is equal to the length of that non-empty string:

x: T and  α = <x>,  then 
| α | = 1 and |α o Λ | = 1;