Index intervals in LYaPAS

The new data type called index interval is proposed for LYaPAS along with the operations defined on members of that type. It enables isolated work on parts of members of another LYaPAS data type, namely the contiguous sequence of homogeneous elements called complex. The syntax for describing the members of the new data type is introduced along with that for the operations on its members. As the implementation detail, the memory layout is discussed. Finally, implementations of some well-known algorithms using index intervals in LYaPAS are given, such as Karatsuba multiplication, quick sort, and the lookup operation in a binary search tree.