Chapter - 2
Data structures for Language
processingAgendaClassificationSearch Data StructureFixed Size
RecordVariable Size RecordHybrid RecordOther OrganizationTree
RepresentationHashed RepresentationAllocation Data StructureStack
& Extended StackHeap
Classification1. Based on nature ---- Linear and Non-linear eg
:- Linear = array , stack etc. Non-Linear = Tree , Graph etc.
2. Based on Purpose --- Search and allocationeg :- Search =
Binary search tree allocation = stacks,heaps
3.Based on Lifetime ---- whether used during Language Processing
or during target program executions eg :- Lang. Processing = Object
based data model Target program = Hash tables Search Data
StructuresA Search data structure (or search structure ) is a set
of entries accommodating the information concerning one entity.
Each entity is assumed to contain a key field which forms the basis
for search . Search Data Structures.. 1Fixed Size RecordVariable
Size RecordHybrid Record
Search Data Structures.. 2Fixed Size RecordVariable Size
RecordHybrid Record
Each entry has same type and sizeEg Array
Search Data Structures.. 3Fixed Size RecordVariable Size
RecordHybrid Record
Type and size of each record could be differentSearch Data
Structures.. 4Fixed Size RecordVariable Size RecordHybrid
Record
Entry has both fixed length part and variable length partEntry
Format
Generic Search Procedure for locating the entry of symbol
Binary Search Organization
Hash Tables
h is the Hashing function.S is the symbols for entryS(e) is
current entry symbol
Hashing FunctionHashing function is used to make search system
faster.It transforms the source symbol or group of symbols to
numerical numbers to make faster comparisons and searchingHashing
do not change the original meaning of symbols it just transforms
them to other form.Size is pre decided for transforming message to
particular formatIf message is of less size than that size , it
performs folding operationIn folding message is padded with 0s to
complete the size of it.
Properties of good hashing func.
Collision in hashingMany function result into same number
generation which leads to collision of numbers and searching will
crash
Thus to avoid collision we have various collision handling
techniques
1. Rehasing technique2. Overflow chaining techniqueAllocation
Data StructureImportant Allocation Data Structures
Stack & Extended StackHeap
Stacks
Extended Stack modelAn extended stack is needed for handling a
variable length record . A record consists of a set of consecutive
stack entriesIn addition to base and top a new pointer Previous is
used.
Heaps
Use of Heap in Memory managementDue to repetition of allocation
and deallocation of memory area holes are created in memory
area.Memory management takes care of this holes and reallocate this
area by managing it properlyIt increases performance and speed of
allocation and deallocation of memory spaces
