Arithmetic Expressions in C++

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Outline Data declaration {section 2.3} Arithmetic operators in C++ {section

2.6} Mixed data type arithmetic in C++ Arithmetic expressions in C++ Operators’ precedence Arithmetic expressions’ evaluation

examples

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Data Declaration Remember the memory anatomy? It is much easier to set aside memory with

names (identifiers). Thus the declaration statements are used to set

aside memory with a specific name for the data and define its values and operations.

type identifier-list; Examples:

char response;char c, grade = ‘A’; int minElement;int n, j = 1;float score;float x, y, z = 40.0;bool flag;

The value can change during execution

-27.2

354

H

75.62

Address Contents

0

1024

1

.

.

.

2

.

.

.

ADD 73

x

n

c

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Data Declaration (cont’d)

When variables are declared

1. Memory allocated for value of specified type

2. Variable name associated with that memory location

3. Memory initialized with values provided (if any)

27

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Constant Declarations A constant is a memory cell whose value cannot

change during execution once it is set in the declartion.

const type constant-identifier = value; E.g.:

const float KM_PER_MILE = 1.609; It is a good C++ programming practice to

capitalize all letters for constant names. Any data type (e.g. int, float, char, or bool)

could be declared as constant.

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Identifiers A valid identifier (variable or function name) must

consist of letters, digits, or underscore only. A valid identifier must not begin with a digit. Valid identifiers: letter, letter1, _letter Invalid identifiers: 1letter, float, hell o You cannot use a C++ reserved word as an identifier. Always try to associate meaningful identifiers. It is a good C++ programming practice to capitalize the

first letter of each word (after the first) when using multiple word identifiers

Remember that C++ is case sensitive (cost != Cost)

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Arithmetic Operators in C+++ Addition- Subtraction* Multiplication/ Division% Modulus (remainder operator, only for integers)

Examples of integer modulus:7 % 2 = 1299 % 100 = 9949 % 5 = 415 % 0 undefined

Examples of integer division (result is integer):15 / 3 = 515 / 2 = 70 / 15 = 015 / 0 undefined

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Mixed Data Type Arithmetic in C++

Example:

4.6 / 2 evaluates to 2.3

Rule: when an integer and a floating point operand are combined by an operator, the integer gets converted to the floating point type.

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Arithmetic Expressions in C++An assignment statement has the following format:

variable = expression;

e.g.:

kms = KM_PER_MILE * miles; The arithmetic expression to the right of the

assignment operator (=) gets evaluated first Then the result is stored in the variable on the

left side of the assignment operator

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Arithmetic Expressions in C++ (cont’d)

Mixed-type assignments:If the variable on left side of assignment is of different type than

the type of the evaluated expression on the right side of =, the result of the expression must be converted to the appropriate type.

Examples:float a, b, x;int m, n;

a = 10; // result is 10.0 stored in ab = 3.5;m = 5;n = 10;x = m / n; // result is 0 assigned to x; therefore x is 0.0m = b * 3; // result is 10 assigned to m

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Arithmetic Expressions in C++ (cont’d)

What if the arithmetic expression contains more than one operator?

x = z - (a + b / 2) + w * -y; How many operators do we have in the above expression? Computers follow operator precedence rules to evaluate

expressions. The formula: m = y - b

x - a The computer equivalent is:

m = (y - b) / (x - a);

Must use ( ) because of operator precedence.

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Order of Operator Precedence ( ) nested expressions

evaluated inside outunary +, -*, /, %

If there are several, then evaluate from left-to-rightbinary +, -

If there are several, then evaluate from left-to-right =

Highest

Lowest

Associativity

Warning: watch out for the types of operands and the type of the result from evaluating each operation!

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Example 1x = z - (a + b / 2) + w * -y; x integer z

a b

w y

3

2-

5

-

7

1

11

8 - (3 + 9 / 2) + 2 * --5 9

8

-5/

4+

x = 8 - (3 + 9 / 2) + 2 * - -5 9 / 2

(3 + 4 ) 8 - 7 + 2 * - - 5 8 - 7 + 2 * 5 8 - 7 + 10 1 + 10

11

* 10

+

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Example 2m = x + k / 2; m integer

x

k

5.5

5/2

convert to float

+ 2.0

7.5

convert to int

7

5.5 + 5 / 2

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Next lecture will be about

Library Functions