437 33 powerpoint-slides chapter-4-functions ch4

7/28/2019 437 33 Powerpoint-slides Chapter-4-Functions Ch4

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Programmingwith ANSI C++,2nd Edition

Prof. Bhushan Trivedi

Director

GLS Institute of Computer Technology


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Chapter 4

Functions


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Similarity and difference withC functions

The function calling, execution and return of aC++ function is technically similar to that of a

C function. C++ has inline functions when programmer

would like to eliminate the overhead ofcontext switching

Also, the object code of the C++ function

contains some additional information then aC function. Main is different here


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Inline fucntionsprovide the flexibility of normal functions and provide efficiency of macrosprecede the function name with keywordinline at the time of definitionmust be defined before usageEliminate the context switching overheadIncrease the program sizeIt is a request


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Default argumentsbool CheckPass(int TotalMarks, intPassingMarks = 50);CheckPass(int Sub1Marks, int Sub2Marks,int PassingMarks = 50)CheckPass(int Sub1Marks, int Sub2Marks,int PassingMarks1 = 50, int PassingMark2 =35);


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Default arguments// following is wrong!CheckPass(int Sub1Marks, intPassingMarks1 = 50, int Sub2Marks, intPassingMark2 = 35);


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Objects as parametersclass Time { }Time Difference(Time , Time);Temporary object creation and NRVoptimization


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Call by and returnreference

Time AddTimes(Time & , Time & );StudList.GetStudent(OriginalName) =NewNode;Returning a temporary object as an aliasof existing variable


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Prototype and overloadingA function prototypeMyFunction(int First, char Second)Overloading a funtionint Add(int, int);double Add(double, double);

string Add(string, string);Overloading does not involve return type


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Other issuesFunction overloading and polymorphismUse and differences between defaultargument and function overloadingsolutionsProgram Readability and Defaultarguments


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Member and non member We need to pass only one argument in place

of two arguments while using a member

function. In the non member case, Difference (Time1,

Time2) or Difference (Time2, Time1) can bepossible.

Non member need either public members or

be friends We do not need an explicit return statement

while using a member function.


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Non friend non member function

The class is not cluttered with unnecessarymember functions and remainsmanageable.The function code is not affected ifprivate variables (the implementation ofthe class) changes, as the function are

not using any private variables


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A friend functionfriend SomeFunction(list of arguments).friend void ListDeptWise(employee[]);A function is not truly a member by naturebut needs access to private membersshould not be made member but a friendFriends violate information hiding principle


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Other issuesConst and Volatile functionsvoid PrintDetails() const { .} void CheckValuesForNIC() volatile {} Mutable data members


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Static functionsstatic int TotalStudents;static void DispTotal();// a declarationvoid student :: DispTotal() // definition {cout


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Static and normal functionsThey do not possess this pointer.They can not access other data membersof the class.They can not be virtual .They can not be declared either const or volatile .


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Returning an objectemployee GetManager(employee EmpArray[])

{

return EmpArray[i]; }}employee GetEmp(string EmpName, employee

EmpArray[]){

for (int i=0;i


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Public and Private functionsclass employee{

bool IsPermanent() /* a private function */{

return (EmpNo > 2000);}


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Non member functionpointers

int (*PointFun)(int,int);// defining pointer to a function which hastwo arguments, both of them are integersTwo ways to call the functioncout


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Member function pointersint PointFunEx :: PointAccess()int (PointFunEx::*PA)(); //a function pointer

PA = PointFunEx :: PointAccess;cout


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Operators :: for defining pointer tofunction and making a call.::* operator to define pointer to amember function.* operator for accessing a member pointer using an object->* operator for accessing a member pointer using pointer to an object.


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Adding C function to aC++ program

C++ decorates the compiled function torepresent its arguments and types of them.

at run time, there is no overhead extern "C" void TestCLinkage(); extern "C" { void TestCLinkage(); void TestCLinkage2(); }

437 33 powerpoint-slides chapter-4-functions ch4

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