UNIT II Structuring the Data, Computations and Program. Kainjan Sanghavi

Transcription

1 UNIT II Structuring the Data, Computations and Program B y Kainjan Sanghavi

2 Contents Monomorphic versus polymorphic type systems Case Study- The type structure of C++ and Java Structuring the computation : Expressions and statements Conditional execution and iteration Routines Style issues: side effects and aliasing Exceptions, Exception Handling in C++

3 Monomorphic Type System In this each and every object belongs to one and only one type. That is here every program entity like constant, variable, routine has a specific type defined by declaration C, Pascal and Ada are not monomorphic in one way or another by virtue of Compatibility Coercion : allows operand of one type to be used for other Overloading : + an * can be used for both integer and real

4 Polymorphic Type System All practical languages have some degree of polymorphism. Hence polymorphism can be classified by different kinds and levels. Polymorphism Universal Adhoc Parametric Inclusion Overloading Coercion

5 Universal Polymorphic Type System Consists of functions that work uniformly for an infinite set of types which have common structure. That is, it executes same code for arguments of all admissible types Parametric : Templates Inclusion : Sub-typing

6 Adhoc Polymorphic Type System Consists of functions that work for an finite and often small set of types They behave differently for each type. Types : Coercion Overloading

7 C++ Types TYPE STRUCTURE OF C++ int INTEGRAL char FUNDAMENTAL FLOATING array enum float double pointer DERIVED function struct Class reference

8 TYPE STRUCTURE OF C++ C++ Types FUNDAMENTAL DERIVED

9 TYPE STRUCTURE OF C++ FUNDAMENTALS INTEGRAL FLOATING

10 TYPE STRUCTURE OF C++ INTEGRAL int char enum

11 TYPE STRUCTURE OF C++ FLOATING float double

12 TYPE STRUCTURE OF C++ DERIVED Array Pointer Functio n Struct / Uniton Class Refere nce

13 Type Structure in Java

14 Type Structure in Java Integers This group includes byte, short, int, and long, which are for whole-valued signed numbers. Floating-point numbers This group includes float and double, which represent numbers with fractional precision. Characters This group includes char, which represents symbols in a character set, like letters and numbers. Boolean This group includes boolean, which is a special type for representing true/false values.

15 Type Structure in Java

16 } Program for Data Type and values public class Demo_datatypes { public static void main(string[] y) { int int_variable=10; float float_variable=(float)10.50; char character_variable=88; char character_variable_char='a'; boolean boolean_variable=false; System.out.println("the int value is"+int_variable); System.out.println("the float value is"+float_variable); System.out.println("the char value is"+character_variable); System.out.println("the char value is"+character_variable_char); System.out.println("the boolean value is"+boolean_variable); }

17 Structuring Computations Expressions in C are basically operators acting on operands. Statements like a = b + 3, ++z and 300 > (8 * k) are all expressions.

18 Conditional and Iterations C C has: if (cond) stmt else stmt while (cond) stmt do stmt while (cond) for (expr; cond; expr) stmt switch (expr) { case expr : stmt;... case expr : stmt; default: stmt }

19 Conditional and Iterations Pascal Pascal has: if cond then stmt else stmt while cond do stmt repeat stmt until cond for id := expr to expr do stmt for id := expr downto expr do stmt case expr of expr : stmt;... expr : stmt; else: stmt; end

20 Conditional and Iterations Ada Ada has: if cond then stmt else stmt endif while cond loop stmt endloop loop stmt exit when cond endloop for id in range Range loop stmt endloop case expr is when expr => stmt; when expr => stmt;... expr : stmt; when others: stmt; end case

21 Side Effects Side Effects is defined as the modifications done to the non-local environment Side Effects can be of two types: Desired Undesired Pass-by-reference, pass-by-name causes side undesired effect. Pass-by-value result also known as pass-by-copy produces desired side effects.

22 Disadvantage of Side Effect Affects Readability Prevents Compiler from generating optimized code.

23 Aliasing Sharing of same memory location by multiple variables Or sharing same data object in a unit activation. If one data object changes its value, all the aliases change.

24 Disadvantage of Aliasing Subprograms become hard to understand Code Optimization too is affected.

25 Exceptions and Exception Handling Refer : Lec40to43: Exception Handling Lec44: Exception HandlingConcepts Lec45: Exception HandlingConcepts

26 Thank You! Angelin