Topics
Terminology
Chapter 3
cin
What does the extraction operator do?Entering multiple values
white space
Program 3-3 - Page 88-89
Mathematical Expressions
z9
z + 9
z * 9
sizeof(z)
z + 5 * 3 / 7
What if
int z = 5;
What is the value of each expression?
Operator Precedence and Associativity
parenthesessizeof
- (unary negation)
* / %
+ - (binary subtraction)
<< >>
Evaluate these expressions
5 + 2 * 6
12 / 4 - 3
3 + 4 * 6 - 2
12 * 18 % 7 - 1
15 - 2 * 6 + 8 - 2
(5 + 2) * 6
12 / (4 - 3)
3 + 4 * (6 - 2)
12 * (18 % 7) - 1
(15 - 2) * (6 + (8 - 2))
5 * sizeof(1000000)
associativity
right to left or left to right
See Appendix C Page 1289
The pow() function
Program 3-5 - Page 96Calculate an average
Program 3-6 - Page 98
Type Conversions
Level of Conversionsexact match
trivial conversion
promotions
standard conversions
floating point type to integer type
demotions
integer type to floating point type
When/How does a conversion occur
assignment
binary operation
cast
Overflow and Underflow
Program 3-7 - Page 102Program 3-8 - Page 103
Cast
C-style cast"old" C++ style functional notation for a cast
static_cast
forces a type conversion
sometimes used to document a conversion (that will take place anyway)
useful for something like, average of three ints:
int a = 2, b = 3, c = 5;
float avg = (a + b + c) / static_cast<float>(3);
Advice: Do not use C-style casts in this class (or even functional notation for a cast). Use static_cast where appropriate.
Multiple Assignment and the Assignment operator
int x = 5, z = 99, q, maybe = 9;
int a = b = c = d = 9; // Why does this work?
Example: Calculate the harmonic mean of the first 5 prime numbers.
The formula for a harmonic mean is 
Example: Calculate the roots of a quadratic equation
A quadratic equation has the formax2 + bx + c = 0
The roots are determined by the formula
Some More Integer Operators
Compound assignment+= -= *= /= %=
Increment and decrement operators
++ prefix and postfix
-- prefix and postfix
Formatted Output
An output stream manipulator changes the behavior of an output stream.The parameterized manipulators require the <iomanip> header file.
The setw manipulator
has a short memory
Program 3-13 - Page 112
The setprecision manipulator
has a long memory
Program 3-15 - Page 114
The fixed and scientific manipulators
have a long memory
Example
| cout
<< setprecision(2); float one = 123.4; float two = 4567.895; float three = 456; float four = 2.89; float five = .895; cout << one << endl; cout << two << endl; cout << three << endl; cout << four << endl; cout << five << endl << endl; cout << fixed; cout << one << endl; cout << two << endl; cout << three << endl; cout << four << endl; cout << five << endl; OUTPUT 1.2e+002 4.6e+003 4.6e+002 2.9 0.89 123.40 4567.90 456.00 2.89 0.89 |
The showpoint manipulator
has a long memory
Example
| cout << setprecision(6); float one = 123.4; float two = 4567.895; float three = 456; float four = 2.89; float five = .895; cout << one << endl; cout << two << endl; cout << three << endl; cout << four << endl; cout << five << endl << endl; cout << showpoint; cout << one << endl; cout << two << endl; cout << three << endl; cout << four << endl; cout << five << endl; OUTPUT 123.4 4567.9 456 2.89 0.895 123.400 4567.90 456.000 2.89000 0.895000 |
The left and right manipulators
have a long memory
Example
| int x = 500; float y = 2.54; string z = "zebra"; cout << x << y << z << endl; cout << setw(8) << x << setw(8) << y << setw(8) << z << endl; cout << left; cout << setw(8) << x << setw(8) << y << setw(8) << z << endl; cout << right; cout << setw(8) << x << setw(8) << y << setw(8) << z << endl; OUTPUT 5002.54zebra 500 2.54 zebra 500 2.54 zebra 500 2.54 zebra |
string input
Example| string
name; int age; cout << "Enter your name "; cin >> name; cout << "Enter your age "; cin >> age; cout << name << age << endl; OUTPUT Enter your name Joe Bentley Enter your age Joe-858993460 |
What happened?
The getline (string) function
reads from an input stream into a stringPrototype
istream& getline (istream& is, string& str);
Example
| string
name; int age; cout << "Enter your name "; getline(cin,name); cout << "Enter your age "; cin >> age; cout << name << age << endl; OUTPUT Enter your name Joe Bentley Enter your age 37 Joe Bentley37 |
char input
The overloaded get function
reads char input from an input streamPrototypes
int istream::get();
istream& istream::get (char& c);
Example
| char a, b; int c; cin.get(a); b = cin.get(); c = cin.get(); cout << a << ' ' << b << ' ' << c << endl; INPUT ABC OUTPUT A B 67 |
The
ignore function
Extract
and discard characters
Prototypeistream& ignore (streamsize n = 1, int delim = EOF);
Program 3-23 - Page 125
Example
string
name;
int age;
cout << "Enter your name ";
cin >> name;
cin.ignore(80,'\n');
cout << "Enter your age ";
cin >> age;
cout << name << age << endl;
int age;
cout << "Enter your name ";
cin >> name;
cin.ignore(80,'\n');
cout << "Enter your age ";
cin >> age;
cout << name << age << endl;
OUTPUT
Enter
your name Joe
Bentley
Enter your age 37
Joe37
Enter your age 37
Joe37
Math Library Functions
- requires #include <cmath>
The rand() function
- returns a random int between 0 and RAND_MAX
- requires #include <cstdlib>
Videos
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istream object
extraction operator
right shift
operator precedence
operator associativity
pow()
conversion
exact match
trivial conversion
promotions
demotions
integer type
floating point type
assignment
assignment operator
binary operator, binary operation
cast
static_cast (operator)
output stream manipulator
<iomanip>
setw
setprecision
fixed
scientific
showpoint
left
right
input buffer
compound assignment operators
+=
-=
*=
/=
%=
increment operator
++
decrement operator
--
prefix
postfix
output stream manipulator
<iomanip>
setw
setprecision
fixed
scientific
showpoint
left
right
input buffer
getline
prototype
get
overloaded
ignore
delimiter
default argument
math library
abs
cos
exp
fmod
log
log10
sin
sqrt
tan
<cmath>
rand()
<cstdlib>
srand
seed a random number generator
time
<ctime>