C++ L02-Conversion+enum+Operators

Mohammad Shaker
mohammadshaker.com
@ZGTRShaker
2010, 11, 12, 13, 14
C++
Programming Language
L02 -CONVERSION+ENUM
+OPERATORS

Type Conversion
•Used when different data types are used together
–Expression
•Arithmetic
•Relational
–Assignment operations
–Parameter passage ( through functions )
–Return type ( From Value-Returning functions )

Type Conversion
•Two types of Conversion:
–Implicit
•Promotion (widening, upcast )
–Promote a smaller type to a larger one
»Thus, no loss of data
–How to promote?
»1st:Promotion
»2nd: Arithmetic
•Demotion
–Demote a larger type to a smaller one
»Thus, maybe loss of data!
–Explicit

Type Conversion –Implicit promotion
•How to promote?
–bool, int, char, short, enum
•Promoted to int
•Integral values that can’t be represented as intare promoted to unsigned
–if the expression still of a mixed type, the follow will be applied:
Long double
double
float
Unsigned long
long
unsigned
int
•Note:
–When using “=” operator, the expression on the right will be converted to the type of the left

Type Conversion –Implicit promotion
float x = 7; // 7 “int” is promoted to float
inti1;
char i2;
float i3;
i1 + i2 + i3
// i1, i2 are promoted to float
3.4 + ‘b’// b “char” is promoted to double
3.43265L + ‘b’// b “int” is promoted to Long double
inti1;
inti2;
double i3;
i1 + i2 + i3
// i1, i2 are promoted to double
inti1;
double i3;
i1 + ‘N’ + i3
// i1, N are promoted to double
intx = 7.4; // 7 “double” is demoted to int= 7 loss of data!

Type Conversion –Explicit promotion
float x = float(7); // becomes 7.0
float x = (float)7;// becomes 7.0
int(7.6)// becomes 7
(int) 7.6// becomes 7
float (7/4) = 1.0
7/4 = 1
float(7) / float(4) = 1.75
double(7) / double(4) = 1.75

Type Conversion –Explicit Casting
#include<iostream>
usingnamespace::std;
voidmain()
{
charc;
inti;
i= c;// implicit casting
cout<< i<< endl;
}
0
#include<iostream>
voidmain()
{
charcece= 'c';
inti;
i= cece; // implicit casting
cout<< i<< endl;
}
99

#include<iostream>
voidmain()
{
charcece= 'c';
inti= cece; // implicit casting
cout<< i<< endl;
}
99
#include<iostream>
voidmain()
{
charcece= 'c';
inti;
i= int(cece); // explicit casting
cout<< i<< endl;
}
99

#include <iostream>
using namespace::std;
void main()
{
char c = 'c';
inti;
i= int(c -'d');// explicit casting
cout<< i<< endl;
}
-1
#include <iostream>
void main()
{
char c = 'c';
inti;
i= int(c -'c');// explicit casting
cout<< i<< endl;
}
0

#include <iostream>
void main()
{
char c = 'c';
inti;
i= int(c -‘2');// explicit casting
cout<< i<< endl;
}
49
#include <iostream>
void main()
{
char c = 'c';
inti;
i= int(c -‘0');// explicit casting
cout<< i<< endl;
}
51

•Types of explicating Casting
–static_cast
–dynamic_cast
–const_cast
–reinterpret_cast

Explicit Casting –static_castAt compile time! Thus, Type & object should be fully known at compile time

Explicit Casting –static_cast
•We were used to do that
•Now, we can do that (Not necessary, just highlighting the cast)
#include<iostream>
voidmain()
{
inti = 25;longl; floatf;
l = i;
f = i;
}
#include<iostream>
voidmain()
{
inti = 25; longl; floatf;
l = static_cast<long>(i1);
f = static_cast<float>(i1);
}

#include<iostream>
voidmain()
{
inti1 = 25;
longi2;
floati3;
i1 = i2;
i1 = i3;
i2 = i3;
}
Compile & Run (with warnings)
#include<iostream>
voidmain()
{
inti1 = 25;
longi2;
floati3;
i1 = static_cast<long>(i2);
i1 = static_cast<float>(i3);
i2 = static_cast<long>(i3);
}
Compile & Run (No warnings since we used static_cast)

Float, double, long double
C++ data types
Structured
Simple
Address
Pointer
Reference
enum
Floating
Array
Struct
Union
Class
Char, Short, int, long, yool
Integral

enum
•Intro
–Deal with limited range of constants (set of constants)
•Set of colors
–Used in place of the actual integer values
–C++ allows creation of a new simple type by listing (enumerating) all the ordered values in the domain of a new type
•Syntax:
enumTypeName{ value1, value2, value3, };

enum
•Declaring variables from the “enumerated” type
#include<iostream>
voidmain()
{
enumCars {Nissan = 1, BMW,Mercedes,Ferrari,Renault};
Cars MyCar, YourCar;
}
#include<iostream>
voidmain()
{
enumCars { Nissan = 1, BMW, Mercedes, Ferrari, Renault } MyCar, YourCar;
}

enum
#include<iostream>
voidmain()
{
enumCars { Nissan, Nissan, Mercedes, Ferrari,Renault};
}
Compiler error. Values must be UNIQUE

enum
#include<iostream>
voidmain()
{
enumCars { Nissan = 1, BMW, Mercedes, Ferrari,Renault};
}
Nissan < BMW < Mercedes <
The Values are ordered from 1upward
Nissan = 1
BMW = 2
Mercedes = 3
#include<iostream>
voidmain()
{
enumCars { Nissan, BMW, Mercedes, Ferrari,Renault};
}
Nissan < BMW < Mercedes <
The defaultValues are ordered from 0 upward
Nissan = 0
BMW = 1
Mercedes = 2

enum
#include<iostream>
voidmain()
{
enumCars {Nissan = 1, BMW, Mercedes = 7, Ferrari, Renault };
cout<< Renault;
}
9
#include<iostream>
voidmain()
{
enumCars { Nissan = 1, BMW, Mercedes = 5, Ferrari,Renault};
}
The Values are incremented by 1
Nissan = 1, BMW = 2
Mercedes = 5, Ferrari = 6, Renault = 7

enum
#include<iostream>
voidmain()
{
enumCars { Nissan = 1, BMW, Mercedes = BMW + 4, Ferrari,Renault= Renault + 2};
}
Complier error Renault undeclared identifier
#include<iostream>
voidmain()
{
enumCars { Nissan = 1, BMW, Mercedes = BMW + 4, Ferrari,Renault= Ferrari + 2};
}
The Values are incremented by 1upward
Nissan = 1, BMW = 2

enum
#include<iostream>
voidmain()
{
enumCars { Nissan = 1, BMW, Mercedes = 1, Ferrari,Renault};
}
The values are ordered from 1upward
Nissan = 1, BMW = 2

enum
#include<iostream>
voidmain()
{
// Declare MyCarof type Cars and initialize it to Nissan
enumCars{ Nissan,BMW,Mercedes,Ferrari,Renault} MyCar= Nissan;
}
Compile and run
#include<iostream>
voidmain()
{
enumCars { Nissan = 1, BMW, Mercedes,Ferrari, Renault };
Cars MyCar, YourCar;
cout<< MyCar;
}
0

enum
#include<iostream>
voidmain()
{
enumCars {Nissan=1,BMW,Mercedes,Ferrari,Renault} MyCar=Nissan;
MyCar= Renault;// legal
inti1 = BMW, i2 = Mercedes;// legal
i2 = Ferrari;// legal
cout<< "i2 = "<< i2 << endl;
}
i2 = 4

enum
#include<iostream>
voidmain()
{
enumCars {Nissan=1,BMW,Mercedes,Ferrari,Renault}MyCar=Nissan;
MyCar= Renault;
inti1 = BMW;
i1 = MyCar;
}
i1 = MyCar; //legal
#include<iostream>
voidmain()
{
enumCars {Nissan=1,BMW,Mercedes,Ferrari,Renault}MyCar=Nissan;
MyCar= Renault;
inti1 = BMW;
MyCar= i1;
}
Compiler error
MyCar= i1; //illegal
Can’t put an integer into an enumtype. guess why?

enum
#include<iostream>
voidmain()
{
enumCars {Nissan,BMW,Mercedes,Ferrari,Renault};
Cars Mine, Yours;
Mine = BMW;
Yours = Mine;
cout<< Yours << endl;
}
1
#include<iostream>
voidmain()
{
enumCars { Nissan, BMW,Mercedes,Ferrari,Renault};
Cars Mine, Yours;
Mine = BMW;
Mine = Yours;
cout<< Mine << endl;
}
0

enum
#include<iostream>
voidmain()
{
enumCars {Nissan, BMW,Mercedes,Ferrari,Renault};
Cars Mine, Yours;
Mine = BMW;
Yours = Mine++;
}
Compiler error
#include<iostream>
voidmain()
{
enumCars {Nissan,BMW,Mercedes,Ferrari,Renault};
Cars Mine, Yours;
Mine = BMW;
Yours = Mine + 1;
}
Compiler error

Operators
•Assignment
–b = 5;// a = 5
–a = 3 + (b = 6 ); // a = 8
–a = b = 5;// legal a = b = 5
•Equality
–2 == 2 // true
–2 == 3 // false
•Arithmetic Operation
–+, -, *, /, %

Operators
•Division /
–The result of division depends on the type of the two operands
•If one of the operands is float
–The result is float typed
•Otherwise
–The result is integer typed
–Examples:
•13 / 4 = 3
•13.0 / 4 = 3.25
•13 / 4.0 = 3.25
•13.0 / 4.0 = 3.25
•Mod %
–Applied to integer types only
–Operands:
•Both positive
–Result is positive
•One or both negative
–Result is machine-dependent

Operators
11.3 % 4;
Compiler error, left side is a double
22 % 7;
1
21 % 7;
0
2%6;
2
23%-6;
5
-23%-6;
-5
2%-6;
2

Operators
•Rules of precedence:
–1st: ()
•When multi nested ()
–Inners come first
–2nd: *, /, %
•Left to right
–3rd: +, -
•Left to right

Operators
voidmain()
{
cout<< (9*2) * 3 / 2 / 2 + (3+2) * (1-10 ) << endl;
}
voidmain()
{
cout<< 9*2 * 3 / 2 / 2 + (3+2) * (1-10 ) << endl;
}
#include<iostream>
voidmain()
{
cout<< 3/2 << endl;
}
voidmain()
{
cout<<(float)3/2<<endl;
system("pause");
}
1 (int)
1.5
-32
-32

Operators
voidmain()
{
cout<< (9*2) * 3 / 2 /* 2 + (3+2) * (1-10 ) << endl;
}
voidmain()
{
intc = 1;
c = 1 + 2;
cout<< c << endl;
c += 2;
cout<< c << endl;
}
voidmain()
{
intc = 1;
c = 1 + 2;
cout<< c << endl;
c = 1;
c += 2;
cout<< c << endl;
}
3
3
Illegal indirection /* compiler error
3
5

Operators
•Special Case:
–When incrementing “+” or decrementing “-” by 1
•All are the same:
b = b + 1;
b += 1;
b++;

Operators
#include<iostream>
voidmain()
{
intc = 1;
c++;
c--;
cout<< c << endl;
}
1
#include<iostream>
voidmain()
{
intc = 1;
++c;
cout<< c << endl;
}
2

Operators
#include<iostream>
voidmain()
{
intc = 1;
--c;
cout<< c << endl;
}
0
#include<iostream>
voidmain()
{
intc;
c = 1;
cout<< c++<< endl;
}
1

Operators
#include<iostream>
voidmain()
{
intc = 1, a;
a = ++c;// a = 2, c = 2
c--;
cout<< a << endl;
}
2
#include<iostream>
voidmain()
{
inti=0;
++i=2;
cout<<i<<endl;
system("pause");
}
2

Operators
#include<iostream>
voidmain()
{
inti=0;
i++=2;
cout<<i<<endl;
system("pause");
}
Compiler error

Relational Operators
voidmain()
{
intc=1, a=0;
if(c==2)
{
c=9;
}
cout<<c<<endl;
system("pause");
}
1
#include<iostream>
voidmain()
{
intc=1, a=0;
if(c++==2)
{
c=9;
}
cout<<c<<endl;
system("pause");
}
2

#include<iostream>
voidmain()
{
intc=1, a=0;
if(++c==2)
{
c=9;
}
cout<<c<<endl;
system("pause");
}
9
#include<iostream>
voidmain()
{
intc=1, a=0;
if(c=2)
{
c=9;
}
cout<<c<<endl;
system("pause");
}
9

#include<iostream>
voidmain()
{
intc=1, a=0;
if(c=2)
{
c=9;
}
cout<<c<<endl;
system("pause");
}
9
#include<iostream>
voidmain()
{
intc=1, a=0;
a=c++;
cout<<a<<endl<<c<<endl;
system("pause");
}
1
2

#include<iostream>
voidmain()
{
intc=1, a=0;
a=++c;
system("pause");
}
2
2

c++
++c
Introduce a L-VALUE nota variable
Introduce a VARIABLE nota value or L-Value

c++
++c
Introduce a VARIABLE nota value or L-Value
Can be assigned!
Can’t be assigned!

c++
•What is l-VALUE?
Expressions that refer to memory locations are called "l-value" expressions. An l-value represents a storage region's "locator" value, or a "left" value, implying that it can appear on the left of the equal sign (=). L-values are often identifiers.

#include<iostream>
voidmain()
{
intc=1, a=0;
c++= a;
system("pause");
}
#include<iostream>
voidmain()
{
intc=1, a=0;
++c = a;
system("pause");
}
Compiler error!
0
0
Variable can be assigned!
l-Value can’t be assigned!

#include<iostream>
voidmain()
{
intc = 1, a = 0;
if(c++> 2 )
{
c = 9;
}
cout<< c << endl;
}
2
#include<iostream>
voidmain()
{
intc = 1, a = 0;
if(c++>= 2 )
{
c = 9;
}
cout<< c << endl;
}
2

#include<iostream>
voidmain()
{
intc = 1, a = 0;
if(++c > 2 )
{
c = 9;
}
cout<< c << endl;
}
2
#include<iostream>
voidmain()
{
intc = 1, a = 0;
if(++c >= 2 )
{
c = 9;
}
cout<< c << endl;
}
9

#include<iostream>
voidmain()
{
intc = 1, a = 0;
if(++c = 2 )
{
c = 9;
}
cout<< c << endl;
}
9

#include<iostream>
voidmain()
{
intc = 1, a = 0;
if(c++= 2)
{
c = 9;
}
cout<< c << endl;
}
Compiler error

#include<iostream>
voidmain()
{
intc = 1, a = 0;
if(c++= 2 )
{
c = 9;
}
cout<< c << endl;
}
Compiler error

#include<iostream>
voidmain()
{
intc = 1, a = 0;
if(c++= 2 )
{
c = 9;
}
cout<< c << endl;
}
Compiler error
l-Value must not be assigned

#include<iostream>
voidmain()
{
intc = 1, a = 0;
if(c++= 2 )
{
c = 9;
}
cout<< c << endl;
}
Compiler error
Let’s roll back to here

#include<iostream>
voidmain()
{
intc = 1, a = 0;
if(c++= 2 )
{
c = 9;
}
cout<< c << endl;
}
Compiler error
Can’t be calculated now!

Relational Operators with strings
•Comparing with collating sequence
•If the strings have different lenghts
–The shorter one is smaller that the larger
str1
= “Hello”
str2
= “Hi”
str3
= “Air”
str4
= “Bill”

Logical Operators
#include<iostream>
voidmain()
{
intc = 1, a = 0;
if((a == 0 ) || (c == 3))
{
c = 9;
}
cout<< c << endl;
}
9

Logical Operators
#include<iostream>
voidmain()
{
intc = 1, a = 0;
if(!(a) > 2 )
{
c = 9;
}
cout<< c << endl;
}
1
#include<iostream>
voidmain()
{
intc = 1, a = 0;
if((a == 2 ) && (c == 3))
{
c = 9;
}
cout<< c << endl;
}
9

Logical Operators
#include<iostream>
voidmain()
{
intc = 1, a;
if((a == 0 ) && (c == 1))
{
c = 9;
}
cout<< c << endl;
}
9
#include<iostream>
voidmain()
{
intc = 1, a;
if((a == 0 ) && (c == 2))
{
c = 9;
}
cout<< c << endl;
}
1

Logical Operators
#include<iostream>
voidmain()
{
intc = 1, a;
if(a == 0 ) && (c == 2)
{
c = 9;
}
cout<< c << endl;
}
Compiler error
#include<iostream>
voidmain()
{
intc = 0, a;
if(( 0 < c ) && ( c <= 12 ))
{
c = 9;
}
cout<< c << endl;
}
0

Logical Operators
•Not always behave as expected
#include<iostream>
voidmain()
{
intc = -1, a;
if( 0 < c <= 12 )
{
c = 9;
}
cout<< c << endl;
}
9
// Always evaluated true!

Conditional Operator?
•Condition? Result1: Result2
•Condition
–If True
•Result1
–Else // condition is false
•Result 2

#include<iostream>
voidmain()
{
intc;
c ==0? c = 2: c = 1;
cout<< c << endl;
}
2
#include<iostream>
voidmain()
{
intc;
c ==2? c = 2: c = 1;
cout<< c << endl;
}
1

#include<iostream>
voidmain()
{
intc;
c!= 0? c = 2: c = 1;
cout<< c << endl;
}
1
#include<iostream>
voidmain()
{
intc;
c ==0? 2: 1;
cout<< c << endl;
}
0

#include<iostream>
voidmain()
{
intc;
c!= 0? 2: 1;
cout<< c << endl;
}
0
#include<iostream>
voidmain()
{
intc;
c!= 0? c=2: 1;
cout<< c << endl;
}
0

#include<iostream>
voidmain()
{
intc;
c = 0? c=2: 1;
cout<< c << endl;
}
1
(c = 0) Simply the variable c is assigned 0
If(zero) returns false

Code Cracking
#include<iostream>
voidmain()
{
enumCars {Nissan,BMW,Mercedes, Ferrari,Renault=Nissan--}; Cars MyCar= Renault;
}
Compiler error Nissan--
#include<iostream>
voidmain()
{
enumCars{Nissan,BMW,Mercedes,Ferrari,Renault++}MyCar=Nissan;
}
Compiler error Renault++, why?

Code Cracking
#include<iostream>
voidmain()
{
enumCars { Nissan = 2.4,BMW,Mercedes,Ferrari,Renault }MyCar= Nissan;
MyCar= Renault;
inti1 = MyCar;
}
Compiler error Nissan = 2.4 must be integer
#include<iostream>
voidmain()
{
intc = 1, a;
if((a = 0 ) && (c = 2))
{
c = 9;
}
cout<< c << endl;
}
9

Code Cracking
#include<iostream>
voidmain()
{
intc = 1, a = 0;
if((a = 3) > 2 )
{
c = 9;
}
cout<< c << endl;
}
9
#include<iostream>
constx = 20;
voidmain()
{
}
2008 Compiler: Compiler error no default intsupported
2005 Compiler: Compile & Run Intassumed

Code Cracking
#include<iostream>
voidmain()
{
intc;
if(c++== 1)
{
cout<< "joo"<<endl;
}
else
{
cout<< "yoo"<< endl;
}
}
yoo
#include<iostream>
voidmain()
{
intc;
if(++c == 1)
{
cout<< "joo"<<endl;
}
else
{
cout<< " "<< endl;
}
}
joo

C++ L02-Conversion+enum+Operators

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