06 Numerical Copy

8/6/2019 06 Numerical Copy

1/14


2/14

COMP 102 Prog Fundamentals I:C++ Numerical Data, Input/Output /Slide 2

Rules forDivision

C++ treats integers differently from decimalnumbers.

100 is an int type. 100.0 , 100.0000, and 100. are double type.

The general rule for division ofint and double

types is: double/double ->double (normal)

double/int ->double (normal)

int/double ->double (normal)

int/int ->int (note: the decimal part is discarded)


3/14


Rules forDivision

Examples: 220. / 100.0 double/double ->double result is 2.2

220. / 100 double/int ->double result is 2.2

220 / 100.0 int/double ->double result is 2.2

220 / 100 int/int ->int result is 2

Summary: division is normal unless both thenumerator and denominator are int, then the resultis an int (the decimal part is discarded).


4/14


Assignment Conversions

A decimal number assigned to an int type variable

is truncated.

An integer assigned to a double type variable is

converted to a decimal number. Example 1:

double yy = 2.7;

int i = 15;

int j = 10;

i = yy; // iisnow 2

yy = j; // yy isnow 10.0


5/14



Example 2:int m,n;

double xx;

m = 7;

n = 2.5;

xx = m / n;

n = xx + m / 2;

// Whatisthe value of n?


6/14



Example 2:int m,n;

double xx;

m = 7;

n = 2.5; // 2.5 convertedto 2 and assignedto n

xx = m/n; // 7/2=3 convertedto 3.0 and assignedto xx

n = xx+m/2;

// m/2=3 : integer division

// xx+m/2 : double addition because xx is double// convert result of m/2 to double (i.e. 3.0)

// xx+m/2=6.0

// convert result of xx+m/2 to int (i.e. 6)

// because nisint


7/14


Forcinga Type Change

You can change the type of an expression with a castoperation.

Syntax:var

iable1 =

type(var

iable2);

variable1 = type(expression);

Example:int x=1, y=2;

double result1 = x/y; // result1 is 0.0

double result2 = double(x)/y; // result2 is 0.5double result3 = x/double(y); // result3 is 0.5

double result4 = double(x)/double(y);// result4is 0.5

double result5 = double(x/y); // result5 is 0.0

int cents = int(result4*100); // centsis 50


8/14


Standard Input/Output

cin - the standard input stream

Input operator >>

Extracts data from input stream (the keyboard by

default).

Skips over white spaces.

Extracts only characters of the right form andperforms automatic conversion to the typespecified.


9/14



cout - the standard output stream

Output operator >score;

cout


10/14



Some special output characters:

\a bell

\t tab

\n new line

\' single quote

\" double quote


11/14


Format Manipulation#include

setw(int size)

Specifies the number of characters to use in displaying the next value,which is right-justified.

Ex: cout


12/14


Format Manipulation

#include

#include

usingnamespace std;

int main(){

cout


13/14

// Demonstrate the features of output formatmanipulators

// Input: cost of lunch,number of people attending lunch

// Output: lunch cost per person

#include// Use IO manipulators

#include

usingnamespace std;int main() {

double cost_of_lunch, cost_per_person;

int number_of_people;

cout cost_of_lunch;

cout >number_of_people;

cost_per_person = cost_of_lunch / number_of_people;

//cout


14/14

cout

Documents

06 Numerical Copy