istream ostream
friend ostream& operator<<(ostream& out, room& r) { out << “Width:” << r.width << “, Length:” << r.length; return out; }
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friend istream& operator>>(istream& in, room& r) { cout << “Enter width: “ << endl; in >> r.width; cout << “Enter length: “ < endl; in >> r.length; return in; }
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Strings vs C-strings (ch8)
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Reading in: |
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>> stops reading at the first space |
string input;
getline(cin, input);
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char input[100]
cin.getline(input, 100);
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empty c-string: char s[20] = "";
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Returning: |
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returning c-strings: return type of pointer. char* funct(){...return...}
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for both: make sure that if you return something in a function if it's a variable defined in the function that is was defined dynamically or is static
. |
Operations: |
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strlen(s)
- s is a c-string cannot use .length() or .size() |
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strcpy(s2, s1)
- copy s1 to s2 |
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strcmp(s1, s2) == 0;
- tests for equality |
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strcat(char* s1, const char* s2);
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string s to double stod(s);
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char* s
to double
: strtod(s, nullptr);
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Functions: |
Random: |
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c-strings have a null termination character '/0'. So to define a c-string to hold 20 it's char input[21];
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same thing as > |
c++ doesn't check indexes to validate if something is within bounds |
int n = 3; cout << (char)(n + '0') << endl;
prints 3. |
char c = 'D'; cout << (c - 'A') << endl;
prints 3. |
char name[100]; char* get_name() { . . . return _______________; }
return name
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Constructors
Default: foo()
no arguments foo f1;
or foo* f2 = new foo;
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Conversion: foo(int i)
one argument to be turned into the class object foo f1(3);
or foo* f2 = new foo(3);
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General: foo(int x, int y)
anything with more than one |
Copy: foo(foo& f)
pointer argument |
Move: foo(foo&& f)
double pointer |
Constructor and Initializer List Examples
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Choose the best C++ class named person that has: A private member field for the person’s first name; A private member field for the person’s last name; A private member field for the person’s age; and a public constructor: class Person{ string first; string last; int age;
public: person(string f, string l, int a) : first(f), last(l), age(a) {} };
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UML: Student
-name: string
-gpa:double
+Student(n: string, g: double) class Student
{private:
string name;
double gpa;
public:
Student(string n, double g) : name(n), gpa(g) {} };
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Write a single constructor that works as default, conversion, and general: UML fraction
-numerator:int
-denominator:int
+fraction(n: int, d:int)
(default values: n = 0, d = 1) fraction(int n = 0, int d = 1) : numerator(n), denominator(d) {}
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UML: Foo
-count:int
+running: bool (set running to true)
+Foo(a_count: int)
-my_helper(arg: int) : char class Foo
{private:
int count;
char my_helper(int arg)
public:
bool running = true;
Foo(int a_count) : count(a_count) {} };
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Extras
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Only technical difference between structures and classes: features in classes are private by default, features in structures are public by default
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Constructors name is the same as the name of the class
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Facts
+: public
-: private
#: protected
underlined:static |
Auto: Stack
Dynamic: Heap |
defining functions outside of a class: return-type class::function-name(arguments)
with a prototype included in class file. |
Member/Friend Summary
member/nonmbr |
Implicit Args |
Explicit Args |
Unary Member: |
1 |
0 |
Unary Friend: |
0 |
1 |
Binary Mbr: |
1 |
1 |
Binary Friend: |
0 |
2 |
mbr/ nonmbr in and out a class
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Mbr defined in the class foo operator+(foo f){...}
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Mbr defined out the class foo foo::operator+(foo f){...}
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Nonmbr defined in the class friend foo operator+(foo f1, foo f2) {...}
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Nonmbr defined out the class foo operator+(foo f1, foo f2) {...}
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Command-line
main function definition to allow a program to access command line arguments: main(int argc, char* argv[])
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A program is named "my_program" and is executed from the command line as my_program file1 file2 file3 file4 If the program is written in C++ and the arguments are passed in to main, what is the value of argc and what is stored in argv[2]?
argc = 5, argv[2] = file2 |
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