[SOLVED] CS compiler Java c++ COMP345:

COMP345:
Advanced Program Design with C++
Lecture 2
C++ Fundamentals
Department of Computer Science and Software Engineering Concordia University

Contents
Data types
Variable declaration and initialization Type checking
Type coercion
Pointers
Strings

Data types
Highly similar to Java data types
Basic types are not classes (like Java)
Pit trap: different compilers will have different ranges for most basic data types Some programs potentially will behave differently across different platforms Hence, lack of portability of C++ programs
User-defined data types using struct (as in C), as well as class (object-oriented programming)
Both are allowed in the same program
In fact, they are almost equivalent, but struct was kept for backward compatibility A struct can have data members, methods, constructors, destructors, etc
One difference is that a struct sets its members as public by default

Data types: simple types size, range and precision

Data types: simple types size, range and precision

Data types: literals
Literals
2, 5.75, Z, Hello World
Considered constants: cant change in program
All literals have an inherent type that can be determined during lexical analysis
Like many other languages, C++ uses escape sequences for string literals:

Contents
Data types
Variable declaration and initialization Type checking
Type coercion
Pointers
Strings

Variable declaration
A variable can be declared for any type valid in the current scope.
int x; double y; myClass mc;
Multiple variables of the same type can be declared on the same declaration: int x,y,z;
Any declared name can be referred to thereafter in the scope in which it is declared.

Variable initialization
Declarations can include an optional initialization, which can use different syntactical forms:
Type a1 {v}; Type a2 = {v}; Type a3 = v; Type a4(v);
All of these are widely used and apparently equivalent. However:
Some are restricted to use in certain situations.
Only the first one is universally usable, and is actually safer, as it implicitly does
some checking of the value passed versus the specified type.
int a1 = 1.5; //allowed using truncation
int a1 {1.5}; //not allowed, as type checking is enforced

Variable initialization
In C++, initialization is a general concept whereby variables are created with an initial value supplied at creation.
This is as opposed to the creation of variables without an initial value, which implies that a memory space is assigned to a variable, but the previously assigned content of the memory space is used.
Initialization is thus safer, but is slightly time-consumptive.
Initialization may seem a simple concept, but in C++ there is a proliferation of rules and special
cases related to initialization.
Rules vary widely across different C++ standards.
Even though you may think that you use simple initialization, expect to be faced with special/obscure cases.
The following slides briefly describe the different kinds of initializations and some simple examples.

Variable initialization
Default initialization: variable is constructed with no initializer.
For basic types, the previous value held in the memory space is kept.
For objects, the default constructor is called.
int x;
std::string s;
classA *objAv1 = new classA;
Value initialization: variable is constructed with an empty initializer. For basic types, the value is zero-initialized.
For objects, each member is value-initialized.
int x{};
std::string s{};
classA objA = classA();

Variable initialization
Direct initialization: variable is constructed using explicit constructor arguments. For basic types, no constructors, but constructor call syntax can be used.
For objects, the corresponding constructor is called
int x(4);
std::string s(hello);
classA objA(value1,value2,value3);
Copy initialization: Variable is created using the value(s) from an existing object of the same type, or uses a converting sequence if available. Applies only to named objects.
std::string s = hello;
classA objAv1; classA objAv2(objAv1);
classA objAv3 = objAv1;
Copy initialization is implicitly used when passing and returning objects by value.

Variable initialization
List initialization: Initializes an object from a braced initialization list.
std::string s{a, b, c};
int n1{1}; // direct-list-initialization int n2 = {1}; // copy-list-initialization
Reference initialization: Binds a reference to an object. char& c = a[0]
int i1; int& iref = &i1
Reference initialization is used implicitly when a value is passed by reference or a reference is returned from a function.

Variable initialization
Aggregate initialization: Initializes an aggregate from braced initialization list. It is list initialization but applied to aggregates.
Simply stated, an aggregate is either: an array
an object of a class that has only public members and no constructors Definition of an aggregate varies between standards.
char a[3] = {a, b};
int i[3] = {1,2,3};
class aggrA{
int a, b, c; aggrB b;
class aggrB{
int x,y; }
}
aggrA a1 = {1,2,3,{4,5}};

Contents
Data types
Variable declaration and initialization Type checking
Type coercion
Pointers
Strings

Type checking, type coercion, type conversion
C++ uses a manifest typing strategy
Variables and values are assigned types explicitly in the source code
Values can only be assigned to variables declared as having the same type
However, C++ allows type coercion, i.e. implicitly or explicitly changing the type of variables or values
This loophole, among other things, makes C++ a weakly typed language Type mismatches
General Rule: Cannot place value of one type into variable of another type
int var = 2.99; // 2 is assigned to var!
Only the integer part fits, so thats all that goes
Called implicit type casting or automatic type conversion When using pointers or classes, much more problematic!

Explicit type casting
C++ provides operators for explicit type coercion, or type casting static_cast (intVar)
Explicitly casts intVar to double type
doubleVar = static_cast (intVar1)/intVar2;
Casting forces double-precision division to take place among two integer variables.
Equivalent in meaning to the following C syntax, even though the C++ cast operation is checked at compile time and is thus less prone to runtime errors
doubleVar = (double)intVar1/intVar2;

Explicit type casting
Different kinds of explicit type casting operations: static_cast (expression)
General-purpose type casting
const_cast (expression)
Cast-out constantness
dynamic_cast (expression)
Runtime-checked conversion of pointers and references within a single class hierarchy. Used for downcasting from a superclass to a subclass
reinterpret_cast (expression)
Implementation-dependent casting, performs a binary copy and assigns the new type to the resulting binary copied value. Highly unsafe and error-prone.

Inheritance: upcasting and downcasting
When dealing with classes and subclasses, one can declare objects of a supertype and manipulate them as one of its subclasses
void displayGeometricObject(GeometricObject& g) {
cout << “The radius is ” << g.getRadius() << endl;cout << “The diameter is ” << g.getDiameter() << endl; cout << “The width is ” << g.getWidth() << endl;cout << “The height is ” << g.getHeight() << endl;cout << “The area is ” << g.getArea() << endl;cout << “The perimeter is ” << g.getPerimeter() << endl;} Problem: subclass members are undefined in superclass GeometricObject ———————- areaperimeterCircle ————radius diameterRectangle ————- width height Inheritance: upcasting and downcasting May want to use static_cast:void displayGeometricObject(GeometricObject& g) {}GeometricObject* p = &g cout << “The radius is ” cout << “The diameter is ” cout << “The width is ” cout << “The height is ” cout << “The area is ” cout << “The perimeter is “<< static_cast (p)->getRadius() << endl; << static_cast (p)->getDiameter() << endl; << static_cast (p)->getWidth() << endl; << static_cast (p)->getHeight() << endl; << g.getArea() << endl;<< g.getPerimeter() << endl; This successfully compiles, but will fail at runtime if the object passed was originally of a type that does not contain the members referred to in the code. static_cast makes a static (compile-time) type cast, but correct runtime behavior cannot be verified. Inheritance: upcasting and downcasting Use dynamic_cast to downcast into a subclass dynamic_cast works on pointers Does runtime checking to verify that the cast is successful Also deals with polymorphic types and virtual methods at runtimeConversion sequences When a variable is declared, it may be initialized using a value that is not of the same type as the variable. The compiler will attempt to find a type conversion sequence that enables it to convert the type of the value intothe type declared for the variable. Two things can be used in a conversion sequence: conversion constructor: a constructor that takes a value of a type and creates an object of another type. A::A(int){…} conversion operator: a member operator that has the name of a type. A::operator int(){…} If you dont want your constructors or operators to be used in a conversion sequence, you have to declare them as explicit in the class declaration explicit B(int); explicit operator bool() const; Contents Data types Variable declaration and initialization Type checking Type coercion Strings pointer Arithmetic pointers/const references smart pointersPointersPointers Variables contain a specific value, e.g., an integer. A pointer variable contains the memory address of a portion of memory that in turncontains a specific value. For any type T, T* is the type pointer to T, i.e. a variable of type T* can hold theaddress of an object of type T. int i = 99; int* p = &i cout << *p << endl; Two operators on pointers:i (int) p (*int) 99&i Dereferencing operator: *, e.g. *p refers to the object pointed to by the pointer. Address operator: &, e.g. &i refers to the address of the first memory cell holding a value. pointers Consider:int *p1, *p2, v1, v2; p1 and p2 are now uninitialized pointers (often called wild pointers). They point to a memory cell whose address corresponds to the value that was already in their cell before allocation. Pointer assignment: p1 = &v1 Sets pointer variable p1 to “point to” the address of variable v1 “p1 equals address of v1” Or “p1 points to v1” v1 (int)v2 (int)p1 (int*)p2 (int*)v1 (int)v2 (int)p1 (int*) &v1 p2 (int*) Pointers Value assignments v1 = 0;v1 (int) 0 v2 (int)p1 (int*) &v1 p2 (int*)v1 (int) 42 v2 (int)p1 (int*) &v1 p2 (int*)*p1 = 42; p1 and v1 refer to same memory cell Changing either the value pointed to by p1 or the value of v1 also changes the other variables value.Pointers Pointer assignment vs value assignment: int v1 = 42;int v2 = 9; int *p2 = &v2 int *p1 = &v1 Pointer assignment: p2 = p1; Assigns one pointer to another “Make p2 point to where p1 points Value assignment: *p2 = *p1; Assigns “value pointed to” by p1, to “value pointed to” by p2 v1 (int) 42 v2 (int) 9 p2 (int*) &v2 p1 (int*) &v1v1 (int)42v2 (int)9 p2 (int*)&v1 p1 (int*)&v1 v1 (int) 42 v2 (int) 42 p2 (int*) &v2 p1 (int*) &v1Pointers Dynamicvariables Require the use of pointers Allocatedwithnewoperator,deallocatedwiththedeleteoperator Need to be allocated and destroyed explicitly while program runs C++ does not have a garbage collector Localvariables Declared within a function definition Not dynamic Allocated on the stack when code block is entered (e.g. function call) Destroyed when code block is exited (e.g. function call completes) Often called “automatic” variables Allocation and deallocation controlled by the runtime system as functions are called Uses a function call stack mechanism to automatically manage memoryallocation/deallocation If pointers are declared in a function The pointer is managed as a local variable The value pointed to is dynamically allocated/deallocated Dynamic/automatic memory allocation:29examplef2() f1(int)int global = 99;int f2(){ int f2x = 3;return (global/f2x); }int f1(int p){// calling this function // creates a memory leak int* f1x = new int(10); return (p + *f1x + f2());}int main(){ int x,y,z;y = 1;z = 2;for (int i = 1; i <= 10; i++){x = f1(y); }}(int) f2x(int) x3(int) p (int*) f1x144(int) y1(int) z2 global(int) global99 10 Concordia UniversityDepartment of Computer Science and Software Engineeringmain() (int)heap stack Pointers The operator new creates dynamically allocated values that can then be pointed to by pointer variables. The value created is a nameless pointer value. Allocated on the heap (also known as freestore) through the runtime systemsinteraction with the operating system. All dynamically allocated variables need to be carefully managed by the programmer. C++ does not have garbage collection. Dynamically allocated variables need to be allocated and deallocated manually Similar to Cs malloc and free Pointersint *p1, *p2;p1 = new int;stackstack heapstack heapstack heap p1 (int*)p2 (int*)p1 (int*)p2 (int*)new intp1 (int*)p2 (int*)*p1 = 42;new int 42p1 (int*) p2 = p1;p2 (int*)new int 42 Pointers*p2 = 53;stack heapstack heapstack heapp1 (int*) p2 (int*)new int 53 p1 (int*)p2 (int*)new int 53 new int p1 (int*)p2 (int*)p1 = new int;new int 53 new int 88Pointers If the type used as parameter is of class type: Constructor is called for new object Can invoke different constructor with initializer arguments: MyClass *myPtr; myPtr = new MyClass(32.0, 17); Can still initialize non-class types:int *n;n = new int(17); //Initializes *n to 17 //That does NOT mean int is a class Pointers Pointers are full-fledged types Can be used just like other types Can be function parameters Can be returned from functions Example: int* findOtherPointer(int* p); This function declaration: Has “pointer to an int” parameter Returns “pointer to an int” Pointers Potential problem if freestore runs out of memory Older compilers: Test if null returned by call to new:int *p;p = new int; if (p == NULL){cout << “Error: Insufficient memory.
“;exit(1); } Most contemporary C++ compilers (C++98 and after) : new throws exception bad_alloc try {int * myarray= new int[1000]; } catch (bad_alloc&) {cout << “Error allocating memory.” << endl; } Pointers To deallocate dynamic memory, use the delete operator When value no longer needed Returns memory to freestore Example:int *p;p = new int(5);… //Some processing… delete p;p = NULL;//allocate memory//deallocate memory//prevents dangling pointer errors Deallocates dynamic memory “pointed to by pointer p ” p is then a dangling pointer that still points to its previously allocated value. If not deleted before the variable goes out of scope, memory is not freed, which creates a memory leak. Plus, dereferencing a dangling pointer leads to unpredictable results, ranging from getting a seemingly random value to a program crash. Managing dangling pointers and deallocating dynamically allocated memory is a very important aspect of proper C++ programming. Pointer arithmetic Can perform arithmetic operations on pointers Used to navigate arrays (covered later) Example:int *d;d = new int[10]; d refers to: address of new int[10] d + 1 refers to: address of new int[10] + 1*sizeof(int) d + 2 refers to: address of new int[10] + 2*sizeof(int) d[i] == *(&d[0]+i) == *(d+i) Pointers and const When using pointers, there are two separate meanings/usages of const: Specify the constantness of the pointer Specify the constantness of the value pointed to.int x;int * p1 = &x // non-const pointer to non-const int const int * p2 = &x // non-const pointer to const int int * const p3 = &x // const pointer to non-const int const int * const p4 = &x// const pointer to const int void, wild, dangling, and null pointersvoid pointer: a pointer that is allowed to be pointing to a value of any type. void increase (void* data, int psize){ if ( psize == sizeof(char) ){ char* pchar; pchar=(char*)data; ++(*pchar); } else if (psize == sizeof(int) ){ int* pint; pint=(int*)data; ++(*pint); }}int main (){char a = ‘x’;int b = 1602;increase (&a,sizeof(a)); increase (&b,sizeof(b));cout << a << “, ” << b << ‘
‘; return 0;}Disadvantage: need to cast them specifically in order to use them.void, wild, dangling, and null pointers wild pointer: a pointer that points to an arbitrary memory location. This is most often due to an uninitialized pointer declarationint *x;Here, x points to the address that corresponds to whatever value that already was in the memory space allocated to x.Dereferencing a wild pointer may lead to: Segmentation fault: pointing to an address that is not accessible by the programs process pointing to an address that contains read-only data Arbitrary value: pointing to a valid address that contains a valid but arbitrary integer valuevoid, wild, dangling, and null pointers dangling pointer: a pointer that used to point to a valid memory area, that has now been potentially reassigned to another usage.int* func(){int num = 1234; // num is local to func /* … */return # // func returns pointer to num} void func(){ClassA *objA = new ClassA(); /* … */delete(objA);}// *objA is deallocated.// objA is now a dangling pointer.// Dereferencing will still appear// to work, until the memory is used// for something else… void, wild, dangling, and null pointers null pointer: a pointer that points nowhere. int* x = nullptr; int* y = NULL; int* z = 0;Dereferencing a null pointer is a compilation error : safer pointer usage.Pointers should be initialized as null pointers. Dangling pointers should be assigned to null.Check for null pointer is then a good way to know if a pointer is valid or not.References Pointers are very powerful, as they allow: A variable to refer a value held by another variable. A variable to refer to different values held by different variables in time. Pass information around without having to copy it. However, due to their power, pointers bring additional complexities: Must use a special syntax (*, &, ->)
Possibility of dangling pointers, wild pointers, null pointers.
Pointers are unsafe, as their use may easily result in undefined behavior.
References are pointer variables that eliminate some of the disadvantages of pointers, at the cost of
eliminating some of their power.
Pointer arithmetic cannot be applied to a reference.
Any operation applied to a reference is actually applied onto the variable it refers to, including assignment.
Hence, references must be initialized upon declaration and cannot be changed afterwards.
Furthermore, given a reference int& r {v1}, &r returns a pointer to the object referred to by r.
Thus, we cannot even have a pointer to a reference.

References
A reference is in fact an alias for a memory space.
Terminology: the reference is an alias to a referent (the value pointed to). Both the reference and the referee represent the same value/object.

References
References are often used to pass parameters:

References
Or even return a value.
In combination, passing a reference and returning a reference allows to pass an object, process it, then return it, allowing the returned reference to be acted upon.

Smart pointers
Pointers are a very good example of a powerful C++ feature that is dangerous to use.
Very powerful and lean tool to use. But leads to:
Memory leaks: if a pointer is declared in a function and not deleted, the value that is pointed to is not freed. Dangling pointers: if a pointer is deleted, the pointer still points to the freed memory block.
Solution: use smart pointers
Reduce bugs
Retain similar efficiency and syntax
Control memory management by methods
auto_ptr (now deprecated), unique_ptr, shared_ptr, weak_ptr Defined in the library

Smart pointers
Smart pointers are conceptually the same as pointers.
Implemented as a template class:
Class that contains a pointer of a variable type.
Implements the *, ->, = operators, constructor and destructor.
template class auto_ptr { T* ptr;
public:
explicit auto_ptr(T* p = 0) : ptr(p) {}
};
~auto_ptr()
T& operator*()
T* operator->()
{delete ptr;}
{return *ptr;}
{return ptr;}
Classes, templates and explicit constructors will be explained later.

Smart pointers
Therefore instead of writing
void foo(){
MyClass* p(new MyClass); p->DoSomething(); delete p;
}
The programmer writes
void foo(){
auto_ptr p(new MyClass);
p->DoSomething();
}

Smart pointers
Here is an example of code which illustrates the situation of a dangling pointer:
MyClass* p(new MyClass);
MyClass* q = p;
delete p;
p->DoSomething();
p = NULL;
q->DoSomething();
// Watch out! p is now dangling!
// p is no longer dangling
// Ouch! q is still dangling!
Problem: p and q are both pointing at the same address space, which is problematic.

Smart pointers
For auto_ptr, this is solved by setting its pointer to NULL when it is copied:
template
auto_ptr & auto_ptr ::operator=(auto_ptr & rhs){
}
if (this != &rhs) {
delete ptr;
ptr = rhs.ptr;
rhs.ptr = NULL; }
return *this;
This implementation prevents a memory space from being pointed to by two different auto_ptr. But maybe we wanted that possibility. Using smart pointers brings its limitations.
There are different variations of smart pointers.

Passing parameters and returning values
Parameters can be passed to a function: Byvalue
A copy of the value is made, then the copied value is passed to the function.
For objects, the copy constructor is called by the runtime system to make the copy.
Thus, the value used in the function is local to the function.
Changing it in the function does not change the value passed from the calling function. Pass by value cannot accept a parameter that is an expression.
Bypointer
A copy of the pointer value is made, then passed to the function.
Thus, both functions are pointing to the same value; no copy of the value pointed to is made. Changing the pointed value in the called function will change the value in the calling function.
Byreference
Conceptually same as pass by pointer, except that the called function cannot change where the
received pointer is pointing.
Drawback: cannot pass NULL , as a reference cannot be NULL
Advantage: can accept unnamed values resulting from the evaluation of expressions as parameters: void f(const T& t); called as f(T(a, b, c)), or f(a+b)
Call by constant reference is very often used to save memory consumption to pass parameters that are not to be changed locally.

Passing parameters and returning values
================= C::C(); ================= address where c is stored : 0068F9B3
passing by value
C::C(C); =================
= pass_by_value
= address where val_c is stored: 0068F8B8
================= passing by reference ================= = pass_by_reference
= address of object that ref_c refers to: 0068F9B3
================= passing by pointer ================= = pass_by_pointer
= address of object pointed to by
ptr_c: 0068F9B3
================= passing/returning by value
C::C(C); ================= address where val_c is stored: 0068F8B8
C::C(C);
passing/returning by reference =================
= address of object that ref_c refers to: 0068F9B3
================= passing/returning by pointer =================
address of object pointed to by ptr_c: 0068F9B3
=================
class C {
public:
C() {cout << “C::C();” << endl;};C(int) { cout << “C::C(int);” << endl; }; C(C&) { cout << “C::C(C);” << endl; }};int main() {cout << “= = = = = = = = = = = = = = = = =” << endl; C c;cout << “= = = = = = = = = = = = = = = = =” << endl; cout << “address where c is stored : ” << &c << endl;cout << “passing by value” << endl; pass_by_value(c);cout << “passing by reference” << endl; pass_by_reference(c);cout << “passing by pointer” << endl; pass_by_pointer(&c);cout << “passing/returning by value” << endl;c = pass_and_return_by_value(c);cout << “passing/returning by reference” << endl; c = pass_and_return_by_reference(c);cout << “passing/returning by pointer” << endl; c = *pass_and_return_by_pointer(&c);return 0; } Passing parameters and returning values void pass_by_value(C val_c) {cout << “= = = = = = = = = = = = = = = = =” << endl;cout << “= pass_by_value ” << endl;cout << “= address where val_c is stored: ” << &val_c << endl << endl;cout << “= = = = = = = = = = = = = = = = =” << endl;}void pass_by_reference(C& ref_c) {cout << “= = = = = = = = = = = = = = = = =” << endl;cout << “= pass_by_reference ” << endl;cout << “= address of object that ref_c refers to: ” << &ref_c << endl << endl; cout << “= = = = = = = = = = = = = = = = =” << endl;}void pass_by_pointer(C* ptr_c) {cout << “= = = = = = = = = = = = = = = = =” << endl;cout << “= pass_by_pointer ” << endl;cout << “= address of object pointed to by ptr_c: ” << ptr_c << endl << endl; cout << “= = = = = = = = = = = = = = = = =” << endl;} Passing parameters and returning values C pass_and_return_by_value(C val_c) {cout << “= = = = = = = = = = = = = = = = =” << endl;cout << “address where val_c is stored: ” << &val_c << endl << endl;// returning by value returns a copy of the local object (copied using the copy constructor). return val_c;}C* pass_and_return_by_pointer(C* ptr_c) {cout << “= = = = = = = = = = = = = = = = =” << endl;cout << “address of object pointed to by ptr_c: ” << ptr_c << endl << endl;cout << “= = = = = = = = = = = = = = = = =” << endl;// Here we return a pointer to the object. //// Returning a pointer the original object is not really useful (though it avoids making a copy of the object).// Really useful if we want to receive an object, do some processing using it,// and return a new object created locally that resides on the heap,// or sometimes receive a null pointer and return a pointer to newly created object. //// if (ptr_c) {// process and change the passed object// } else {// do some processing and create a new pointer to a C // }return ptr_c;}C& pass_and_return_by_reference(C& ref_c) {cout << “= = = = = = = = = = = = = = = = =” << endl;cout << “= address of object that ref_c refers to: ” << &ref_c << endl << endl; cout << “= = = = = = = = = = = = = = = = =” << endl;// here we return the original reference //// Use this if you want the calling function to use the function call as a value part of an expression.// The most famous example of pass-and-return-by reference is the implementation// of stream extraction/insertion operators (<>). //
// Limitation: as a reference cannot be made to point to a new object or to be null,
// passing/returning by pointer is often the appropriate solution. return ref_c;
}

Contents
Data types
Variable declaration and initialization Type checking
Type coercion
Pointers
Strings

Strings
C++ provides following two types of string representations: C-style character strings
string class type introduced with Standard C++
Many libraries would define their own string type
You will encounter many different ways of declaring/manipulating strings.

C-style character strings
With C-style character strings, strings are arrays of characters terminated by a null character ()
char greeting[6] = {H, e, l, l, o, };
char greeting[] = Hello;
provides many string manipulation functions strcpy(s1,s2): copy string s2 into string s1
strcat(s1,s2): concatenate string s2 onto the end of string s1
strlen(s1): returns the length of string s1
strcmp(s1,s2): returns lexical distance between s1 and s2
strchr(s1,ch): returns a pointer to the first occurrence of character ch in s1
strstr(s1,s2): returns a pointer to the first occurrence of string s2 in string s1

Strings: example of C-style strings
#include
#include
using namespace std;
int main (){
char str1[10] = Hello;
char str2[10] = World;
char str3[10];
int len ;
// copy str1 into str3: PROBLEM!!
strcpy(str3, str1);
cout << “strcpy(str3, str1) : ” << str3 << endl; // concatenates str1 and str2: PROBLEM!! strcat(str1, str2); cout << “strcat(str1, str2): ” << str1 << endl; // total length of str1 after concatenation len = strlen(str1); cout << “strlen(str1) : ” << len << endl;return 0; } Standard C++ string class The standard C++ library provides a string class
Provides all the operations mentioned above, using a more natural object- oriented style.

Standard C++ string class
62
Concordia University Department of Computer Science and Software Engineering

Standard C++ string class: example
#include
#include
using namespace std;
int main (){
string str1 = Hello;
string str2 = World;
string str3;
int len ;
// copy str1 into str3
str3 = str1;
cout << “str3 : ” << str3 << endl;// concatenates str1 and str2str3 = str1 + str2;cout << “str1 + str2 : ” << str3 << endl;// total length of str3 after concatenation len = str3.size();cout << “str3.size() : ” << len << endl;// compare two stringscout << “str1 is lexically ” << (str1.compare(str2)) << ” away from str2″ << endl; return 0;}63Concordia University Department of Computer Science and Software Engineering References Y. Daniel Liang, Introduction to Programming with C++ (Chapter 1, 11, 13, 15), Peason, 2014. Bjarne Stroustrup, The C++ Programming Language (Chapter 6, 7, 11, 22), Addison-Wesley, 2013. TutorialsPoint. Learn C++ Programming Language (Chapter 17). cplusplus.com. class documentation.
cppreference.com. initialization.
cplusplus.com. Pointers.
learncpp.com. Returning by value, reference, and address.
isocpp.org. References.
Joey Paquet COMP345 course Notes Concordia university.