Transcript Document

CHAPTER:8
OPERATORS AND EXPRESSION IN C++
Prepared By :
VINAY ALEXANDER (विनय अलेक्सजेंड़र)
PGT(CS) ,KV JHAGRAKHAND
=> OPERATORS: “An operator is a
symbol (+,-,*,/) that directs the
computer to perform certain
mathematical or logical manipulations
and is usually used to manipulate data
and variables”
=>The objects of the operation(s) are
referred to as Operands.
Ex:
a+b
operands
Operator
Arithmetic Operators
=>Unary Operator: It act on one operand .
=> Unary +: The operator unary ‘+’ precedes an
operand.
Example: if a=5 then +a means 5.
=> Unary -: The operator unary ‘-’ precedes an
operand.
Example: if a=5 then -a means -5.
Arithmetic Operators
=>Arithmetic operators +, -, * are the same
as in math
=>Division operator / if used on integers
returns integer (without rounding) or
exception
=>Division operator / if used on real
numbers returns real number or Infinity or
NaN
=>Remainder operator % returns the
remainder from division of integers.
If nominator is less than denominator then
remainder is always the nominator value.
=> Binary Operator: It act upon two
operands .
Arithmetic operators
Operator
+
*
/
Description
Adds two operands
Subtracts second operand from
the first
Multiply both operands
Divide numerator by denumerator
Example
A + B will give 30
,if A=20 and B=10
A - B will give -10
A * B will give 200
B / A will give 2
%
Modulus Operator and remainder
B % A will give 0
of after an integer division
++
Increment operator, increases
integer value by one
A++ will give 11
Decrement operator, decreases
integer value by one
A-- will give 9
--
Increment(++) & Decrement(– –)
Operators
C++ supports 2 useful operators
namely
1. Increment ++
2. Decrement – – operators
=>The ++ operator adds a value 1 to
the operand
=>The – – operator subtracts 1 from
the operand
++a
//pre-increment
a++ //post-increment
– –a //pre- Decrement
a– – //post- Decrement
Rules for ++ & -- operators
1. These
require
variables
as
their
operands
2. The postfix either ++ or – – operators
follow use-then-change rule i.e., they first
use the value of their operand in evaluating
the expression and then change(++/ – – ) the
operand value .
3. The prefix either ++ or – – operators
follow change-then-use rule i.e., they first
change(++/ – – ) the value of their operand,
then use the new value in evaluating the
expression.
Note: In Turbo C++, First all prefix
operators are evaluated prior to expression
evaluation.
Examples for ++ & -- operators
Let the value of a =5 and b=++a then
a = b =6
Let the value of a = 5 and b=a++ then
a =6 but b=5
i.e.:
1. a prefix operator first adds 1 to the
operand and then the result is
assigned to the variable on the left
2. a postfix operator first assigns the
value to the variable on left and then
increments the operand.
Q.1: Evaluate z=++x + x++ if x=10 initially.
Output:22
Q.2.Find the output of the following code
segment.
int n=7;
cout<<“n++=“<<n++<<“,n=“<<n;
Output: n++=7 ,n=8
Q.2.Find the output of the following code
segment.
int n=7;
cout<<“++n=“<<++n<<“,n=“<<n;
Output: ++n=8 ,n=8
Relational Operators: The relational
operators determine the relation
among different operands.
Operator
Meaning
<
Is less than
<=
Is less than or equal to
>
Is greater than
>=
Is greater than or equal to
==
Equal to
!=
Not equal to
Operator
==
!=
>
<
>=
<=
Description
Checks if the value of two operands is
equal or not, if equal then condition
becomes true.
Checks if the value of two operands is
equal or not, if values are not equal then
condition becomes true.
Checks if the value of left operand is
greater than the value of right operand,
if yes then condition becomes true.
Checks if the value of left operand is
less than the value of right operand, if
yes then condition becomes true.
Checks if the value of left operand is
greater than or equal to the value of
right operand, if yes then condition
becomes true.
Checks if the value of left operand is
less than or equal to the value of right
operand, if yes then condition becomes
Example
(A == B) is true.
(A != B) is true.
(A > B) is true.
(A < B) is true.
(A >= B) is true.
(A <= B) is true.
Logical Operators:
There are following logical operators supported by
C++ language
Operator
Meaning
&&
Logical AND
||
Logical OR
!
Logical NOT
Logical expression or a compound relational expression:
An expression that combines two or more relational
expressions
Ex: if (a==b && b==c)
operator
&&
Description
Example
Called Logical AND operator. If (A && B) is false.
both the operands are non zero If any input values
then condition becomes true.
is zero
||
Called Logical OR Operator. If
any of the two operands is non
(A || B) is true.
zero then condition becomes
true.
!
Called Logical NOT Operator.
Use to reverses the logical
state of its operand. If a
condition is true then Logical
NOT operator will make false.
!(A && B) is true.
Truth Table
a b
0 0
Value of the expression
a && b
a || b
0
0
0 1
0
1
1 0
1 1
0
1
1
1
Conditional(Ternary) operators
Syntax:
exp1 ? exp2 : exp3
Where exp1,exp2 and exp3 are expressions
Working of the ? Operator:
Exp1 is evaluated first, if it is nonzero(1/true)
then the expression2 is evaluated and this
becomes the value of the expression,
If exp1 is false(0/zero) exp3 is evaluated and its
value becomes the value of the expression
Ex: m=2;
n=3
r=(m>n) ? m : n;
Output: r=3
Assignment Operators:
Operator
=
Description
Simple assignment operator, Assigns values from right side
operands to left side operand
Example
C = A + B will assign value of
A + B into C
+=
Add AND assignment operator, It adds right operand to the left C += A is equivalent to C = C +
operand and assign the result to left operand
A
-=
Subtract AND assignment operator, It subtracts right operand C -= A is equivalent to C = C from the left operand and assign the result to left operand
A
*=
Multiply AND assignment operator, It multiplies right operand C *= A is equivalent to C = C *
with the left operand and assign the result to left operand
A
/=
Divide AND assignment operator, It divides left operand with
the right operand and assign the result to left operand
C /= A is equivalent to C = C / A
%=
Modulus AND assignment operator, It takes modulus using two C %= A is equivalent to C = C
operands and assign the result to left operand
%A
<<=
Left shift AND assignment operator
C <<= 2 is same as C = C << 2
>>=
Right shift AND assignment operator
C >>= 2 is same as C = C >> 2
&=
Bitwise AND assignment operator
C &= 2 is same as C = C & 2
^=
bitwise exclusive OR and assignment operator
C ^= 2 is same as C = C ^ 2
|=
bitwise inclusive OR and assignment operator
C |= 2 is same as C = C | 2
Special operators
1.
2.
3.
4.
Comma operator ( ,)
sizeof operator – sizeof( )
Pointer operators – ( & and *)
Member selection operators – ( . and ->)
Operator
sizeof
,
Description
sizeof operator returns the size of a variable. For
example sizeof(a), where a is integer, will return 2.
Comma operator causes a sequence of operations
to be performed. The value of the entire comma
expression is the value of the last expression of the
comma-separated list.
. (dot) and Member operators are used to reference individual
-> (arrow) members of classes, structures, and unions.
&
Pointer operator & returns the address of an
variable. For example &a; will give actual address
of the variable.
*
Pointer operator * is pointer to a variable. For
example *var; will pointer to a variable var.
Precedence of operators: Operator precedence
determines the grouping of terms in an
expression. This affects how an expression is
evaluated.
Certain
operators
have
higher
precedence than others; for example, the
multiplication operator has higher precedence
than the addition operator:
=>BODMAS
RULE:
Brackets
of
Division
Multiplication Addition Subtraction
Brackets will have the highest precedence and have
to be evaluated first, then comes of , then comes
division,
multiplication,
addition
and
finally
subtraction.
C++ language uses some rules in evaluating the
expressions and they r called as precedence rules
or sometimes also referred to as hierarchy of
operations, with some operators with highest
precedence and some with least.
The 2 distinct priority levels of arithmetic operators
in c++ areHighest priority : * / %
Lowest priority : + -
Rules for evaluation of expression
1.
2.
3.
4.
5.
6.
First parenthesized sub expression from left
to right are evaluated.
If parentheses are nested, the evaluation
begins with the innermost sub expression
The precedence rule is applied in determining
the order of application of operators in
evaluating sub expressions
The associatively rule is applied when 2 or
more operators of the same precedence level
appear in a sub expression.
Arithmetic expressions are evaluated from
left to right using the rules of precedence
When parentheses are used, the expressions
within parentheses assume highest priority
Here operators with the highest precedence appear at the
top of the table, those with the lowest appear at the bottom.
Within an expression, higher precedence operators will be
evaluated first.
Category
Postfix
Unary
Multiplicative
Additive
Shift
Relational
Equality
Bitwise AND
Bitwise XOR
Bitwise OR
Logical AND
Logical OR
Conditional
Assignment
Comma
Operator
() [] -> . ++ - -
Associativity
Left to right
+ - ! ~ ++ - - (type)* & sizeof
Right to left
*/%
+<< >>
< <= > >=
== !=
&
^
|
&&
||
?:
Left to right
Left to right
Left to right
Left to right
Left to right
Left to right
Left to right
Left to right
Left to right
Left to right
Right to left
= += -= *= /= %=>>= <<= &= ^= |= Right to left
,
Left to right
Example 1
Evaluate
x1=(-b+ sqrt (b*b-4*a*c))/(2*a) @ a=1, b=-5,
c=6
=(-(-5)+sqrt((-5)(-5)-4*1*6))/(2*1)
=(5 + sqrt((-5)(-5)-4*1*6))/(2*1)
=(5 + sqrt(25 -4*1*6))/(2*1)
=(5 + sqrt(25 -4*6))/(2*1)
=(5 + sqrt(25 -24))/(2*1)
=(5 + sqrt(1))/(2*1)
=(5 + 1.0)/(2*1)
=(6.0)/(2*1)
=6.0/2 = 3.0
Arithmetic Expressions
Relational Expressions
Compound Expressions
Arithmetic Expressions
can either be integer
expressions
or
real
expressions. Sometimes
a mixed expressions can
also be formed which is
a mixer of real and
integer expressions.
• Integer Expressions are formed by
connecting integer constants and/or
integer
variables using integer
arithmetic operators. The following
are valid integer expressions :
• int I,J,K,X,Y,Z,count;
• A) k - x
• B) k + x – y + count
• C) –j + k * y
• D) z % y
• Real Expressions are formed by
connecting real constants and/or
real variables using real arithmetic
operators. The following are valid
real expressions:
• float qty,amount,,value;
• double fin,inter; const bal=250.53;
• i) qty/amount
• ii) (amount + qty*value)-bal
• iii) fin + qty* inter
• iv) inter – (qty * value) + fin
The process of converting one
predefined type into another
is called Type Conversion.
C++ facilitates the type
conversion in two forms:
An implicit type conversion is a
conversion performed by the compiler
without programmer’s intervention.
An implicit conversion is applied
generally whenever differing data
type are intermixed in an expression,
so as not to lose information.
An
explicit
type
conversion is user-defined
that forces an expression
to be of specific type.
The C++ compiler converts
all operands upto the type of
the largest operand, which is
called Type Promotion.
The
explicit
conversion of
an
operand
to
a
specific
type
is
called type casting.
The
expressions
that
result into 0(false) or
1(true) are called logical
expressions. The logical
expressions
are
combination of constants,
variables and relational
operators.
A
Logical
Expressions
may
contain
just
one
signed
or
unsigned variable or a constants,
or it may have two or more
variables or/and constants, or two
or more expressions joined
by
valid relational and/or logical
operators. Two or more variables
or operators should not occur in
continuation.
 An expression is composed of one
or more operations. An expression
terminated
by
semicolon(;)
becomes a statement. Statements
form the smallest executable unit
within a C++ program.
 An assignment statement assigns
value to a variable. The value
assigned may be a constant,
variable or a expression.
 Example: a=cve;
The value of the right side
(expression side) of the
assignment is converted
to the type of the left side
(target variable).
=> int x; char ch;
ch=x;
Target Type
Expression Type
Possible Info
Loss
signed char
char
char
short int
High-order 8 bits
char
int
High-order 8 bits
char
long int
High-order 8 bits
int
long int
High-order 16 bits
int
float
Fractional part and
possibly more
float
double
Precision, result rounded
double
long double
Precision, result rounded
If value >127, target is
negative
 C++ offers special shorthands that
simplify the coding of a certain type of
assignment statement.
 Following are some example of C++
shorthands:
 x - = 10 ;
equivalent to x = x – 10;
x * = 3 ;
equivalent to x = x * 3;
x / = 2 ;
equivalent to
x = x/2 ;
x % = z ;
equivalent to x = x % z ;
=>END