operators and expressions
DESCRIPTION
Operators and Expressions. Performing Simple Calculations with C#. Svetlin Nakov. Telerik Corporation. www.telerik.com. Table of Contents. Operators in C # and Operator Precedence Arithmetic Operators Logical Operators Bitwise Operators Comparison Operators Assignment Operators - PowerPoint PPT PresentationTRANSCRIPT
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Operators and Expressions
Performing Simple Calculations with C#
Svetlin NakovTelerik
Corporationwww.telerik.com
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Table of Contents1. Operators in C# and Operator
Precedence2. Arithmetic Operators3. Logical Operators4. Bitwise Operators5. Comparison Operators6. Assignment Operators7. Other Operators8. Implicit and Explicit Type
Conversions9. Expressions
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Operators in C#Arithmetic, Logical, Comparison,
Assignment, Etc.
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What is an Operator? Operator is an operation
performed over data at runtime Takes one or more arguments
(operands) Produces a new value
Operators have precedence Precedence defines which will be
evaluated first Expressions are sequences of
operators and operands that are evaluated to a single value
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Operators in C# Operators in C# :
Unary – take one operand Binary – take two operands Ternary (?:) – takes three operands
Except for the assignment operators, all binary operators are left-associative
The assignment operators and the conditional operator (?:) are right-associative 5
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Categories of Operators in C#
Category OperatorsArithmetic + - * / % ++ --Logical && || ^ !Binary & | ^ ~ << >>Comparison == != < > <= >=
Assignment = += -= *= /= %= &= |= ^= <<= >>=
String concatenation +
Type conversion is as typeofOther . [] () ?: new
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Operators Precedence
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Operators PrecedencePrecede
nce OperatorsHighest ()
++ -- (postfix) new typeof++ -- (prefix) + - (unary) ! ~* / %+ -<< >>< > <= >= is as== != &
Lower ^8
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Operators Precedence (2)
Precedence Operators
Higher |&&||?:
Lowest = *= /= %= += -= <<= >>= &= ^= |=
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Parenthesis operator always has highest precedence
Note: prefer using parentheses, even when it seems stupid to do so
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Arithmetic Operators
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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
The special addition operator ++ increments a variable
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Arithmetic Operators – Example
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int squarePerimeter = 17;double squareSide = squarePerimeter / 4.0;double squareArea = squareSide * squareSide;Console.WriteLine(squareSide); // 4.25Console.WriteLine(squareArea); // 18.0625
int a = 5;int b = 4;Console.WriteLine( a + b ); // 9Console.WriteLine( a + b++ ); // 9Console.WriteLine( a + b ); // 10Console.WriteLine( a + (++b) ); // 11Console.WriteLine( a + b ); // 11
Console.WriteLine(12 / 3); // 4Console.WriteLine(11 / 3); // 3
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Arithmetic Operators –Example (2)
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Console.WriteLine(11.0 / 3); // 3.666666667Console.WriteLine(11 / 3.0); // 3.666666667Console.WriteLine(11 % 3); // 2Console.WriteLine(11 % -3); // 2Console.WriteLine(-11 % 3); // -2
Console.WriteLine(1.5 / 0.0); // InfinityConsole.WriteLine(-1.5 / 0.0); // -InfinityConsole.WriteLine(0.0 / 0.0); // NaN
int x = 0;Console.WriteLine(5 / x); // DivideByZeroException
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Arithmetic Operators –Overflow Examples
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int bigNum = 2000000000;int bigSum = 2 * bigNum; // Integer overflow!Console.WriteLine(bigSum); // -294967296
bigNum = Int32.MaxValue;bigNum = bigNum + 1;Console.WriteLine(bigNum); // -2147483648
checked{ // This will cause OverflowException bigSum = bigNum * 2;}
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Arithmetic OperatorsLive Demo
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Logical Operators
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Logical Operators Logical operators take boolean operands and return boolean result
Operator ! turns true to false and false to true
Behavior of the operators &&, || and ^ (1 == true, 0 == false) :
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Operation || || || || && && && && ^ ^ ^ ^
Operand1 0 0 1 1 0 0 1 1 0 0 1 1
Operand2 0 1 0 1 0 1 0 1 0 1 0 1
Result 0 1 1 1 0 0 0 1 0 1 1 0
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Logical Operators – Example
Using the logical operators:
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bool a = true;bool b = false;Console.WriteLine(a && b); // FalseConsole.WriteLine(a || b); // TrueConsole.WriteLine(a ^ b); // TrueConsole.WriteLine(!b); // TrueConsole.WriteLine(b || true); // TrueConsole.WriteLine(b && true); // FalseConsole.WriteLine(a || true); // TrueConsole.WriteLine(a && true); // TrueConsole.WriteLine(!a); // FalseConsole.WriteLine((5>7) ^ (a==b)); // False
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Logical OperatorsLive Demo
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Bitwise Operators
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Bitwise Operators Bitwise operator ~ turns all 0 to 1 and
all 1 to 0 Like ! for boolean expressions but bit
by bit The operators |, & and ^ behave like ||, && and ^ for boolean expressions but bit by bit
The << and >> move the bits (left or right)
Behavior of the operators|, & and ^:21
Operation | | | | & & & & ^ ^ ^ ^
Operand1 0 0 1 1 0 0 1 1 0 0 1 1Operand2 0 1 0 1 0 1 0 1 0 1 0 1Result 0 1 1 1 0 0 0 1 0 1 1 0
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Bitwise Operators (2) Bitwise operators are used on integer numbers (byte, sbyte, int, uint, long, ulong)
Bitwise operators are applied bit by bit
Examples:
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ushort a = 3; // 00000000 00000011ushort b = 5; // 00000000 00000101Console.WriteLine( a | b); // 00000000 00000111Console.WriteLine( a & b); // 00000000 00000001Console.WriteLine( a ^ b); // 00000000 00000110Console.WriteLine(~a & b); // 00000000 00000100Console.WriteLine( a << 1); // 00000000 00000110Console.WriteLine( a >> 1); // 00000000 00000001
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Bitwise Operators – Tips & Tricks
How to get the bit at position p in a number n?
How to set the bit at position p to 0?
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int p = 5;int n = 35; // 00000000 00100011int mask = 1 << p; // 00000000 00100000int nAndMask = n & mask; // 00000000 00100000int bit = nAndMask >> p; // 00000000 00000001Console.WriteLine(bit); // 1
int p = 5;int n = 35; // 00000000 00100011int mask = ~(1 << p); // 11111111 11011111int result = n & mask; // 00000000 00000011Console.WriteLine(result); // 3
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Bitwise Operators – Tips & Tricks (2)
How to set the bit at position p to 1?
How to print a binary number to the console?
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int p = 4;int n = 35; // 00000000 00100011int mask = 1 << p; // 00000000 00010000int result = n | mask; // 00000000 00110011Console.WriteLine(result); // 51Console.WriteLine( Convert.ToString(result, 2).PadLeft(32, '0'));// 00000000000000000000000000110011
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Bitwise OperatorsLive Demo
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Comparison and Assignment Operators
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Comparison Operators Comparison operators are used to compare variables ==, <, >, >=, <=, !=
Comparison operators example:
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int a = 5;int b = 4;Console.WriteLine(a >= b); // TrueConsole.WriteLine(a != b); // TrueConsole.WriteLine(a == b); // FalseConsole.WriteLine(a == a); // TrueConsole.WriteLine(a != ++b); // FalseConsole.WriteLine(a > b); // False
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Assignment Operators Assignment operators are used to
assign a value to a variable , =, +=, -=, |=, ...
Assignment operators example:
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int x = 6;int y = 4;Console.WriteLine(y *= 2); // 8int z = y = 3; // y=3 and z=3 Console.WriteLine(z); // 3Console.WriteLine(x |= 1); // 7Console.WriteLine(x += 3); // 10Console.WriteLine(x /= 2); // 5
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Comparison and Assignment Operators
Live Demo
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Other Operators
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Other Operators String concatenation operator + is used to concatenate strings
If the second operand is not a string, it is converted to string automatically
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string first = "First";string second = "Second";Console.WriteLine(first + second); // FirstSecondstring output = "The number is : ";int number = 5;Console.WriteLine(output + number);// The number is : 5
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Other Operators (2) Member access operator . is used to access object members
Square brackets [] are used with arrays indexers and attributes
Parentheses ( ) are used to override the default operator precedence
Class cast operator (type) is used to cast one compatible type to another
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Other Operators (3) Conditional operator ?: has the form
(if b is true then the result is x else the result is y)
The new operator is used to create new objects
The typeof operator returns System.Type object (the reflection of a type)
The is operator checks if an object is compatible with given type
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b ? x : y
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Other Operators Null-coalescing operator ?? is used to define a default value for both nullable value types and reference types It returns the left-hand operand if it
is not null Otherwise it returns the right
operand
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int? x = null;int y = x ?? -1;
int? x = 1;int y = x ?? -1;
Here the value of y is -1
Here the value of y is 1
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Other Operators – Example
Using some other operators:
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int a = 6;int b = 4;Console.WriteLine(a > b ? "a>b" : "b>=a"); // a>bConsole.WriteLine((long) a); // 6
int c = b = 3; // b=3; followed by c=3;Console.WriteLine(c); // 3Console.WriteLine(a is int); // TrueConsole.WriteLine((a+b)/2); // 4Console.WriteLine(typeof(int)); // System.Int32
int d = new int();Console.WriteLine(d); // 0
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Other OperatorsLive Demo
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Implicit and Explicit Type Conversions
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Implicit Type Conversion
Implicit type conversion Automatic conversion of value of
one data type to value of another data type
Allowed when no loss of data is possible "Larger" types can implicitly take
values of smaller "types" Example:
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int i = 5;long l = i;
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Explicit Type Conversion
Explicit type conversion Manual conversion of a value of one
data type to a value of another data type
Allowed only explicitly by (type) operator
Required when there is a possibility of loss of data or precision
Example:39
long l = 5;int i = (int) l;
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Type Conversions – Example
Example of implicit and explicit conversions:
Note: Explicit conversion may be used even if not required by the compiler 40
float heightInMeters = 1.74f; // Explicit conversiondouble maxHeight = heightInMeters; // Implicit
double minHeight = (double) heightInMeters; // Explicit
float actualHeight = (float) maxHeight; // Explicit
float maxHeightFloat = maxHeight; // Compilation error!
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Type ConversionsLive Demo
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Expressions
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Expressions Expressions are sequences of operators, literals and variables that are evaluated to some value
Examples:
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int r = (150-20) / 2 + 5; // r=70// Expression for calculation of circle areadouble surface = Math.PI * r * r;// Expression for calculation of circle perimeterdouble perimeter = 2 * Math.PI * r;
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Expressions (2) Expressions have:
Type (integer, real, boolean, ...) Value
Examples:
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int a = 2 + 3; // a = 5int b = (a+3) * (a-4) + (2*a + 7) / 4; // b = 12bool greater = (a > b) || ((a == 0) && (b == 0));
Expression of type int.
Calculated at compile time.
Expression of
type int. Calculat
ed at runtime.
Expression of type bool. Calculated at
runtime.
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ExpressionsLive Demo
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Summary We discussed the operators in C#:
Arithmetic, logical, bitwise, comparison, assignment and others
Bitwise calculations Operator precedence
We learned when to use implicit and explicit type conversions
We learned how to use expressions
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Resources Boolean algebra (logic)
http://en.wikipedia.org/wiki/Boolean_algebra_%28logic%29
Bitwise mask http://en.wikipedia.org/wiki/Mask_%
28computing%29 Bitwise operation
http://en.wikipedia.org/wiki/Bitwise_operation
Bit Twiddling Hacks graphics.stanford.edu/~
seander/bithacks.html
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Questions?
Questions?
Operators and Expressions
http://academy.telerik.com
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Exercises1. Write an expression that checks if
given integer is odd or even.2. Write a boolean expression that checks
for given integer if it can be divided (without remainder) by 7 and 5 in the same time.
3. Write an expression that calculates rectangle’s area by given width and height.
4. Write an expression that checks for given integer if its third digit (right-to-left) is 7. E. g. 1732 true.
5. Write a boolean expression for finding if the bit 3 (counting from 0) of a given integer is 1 or 0.
6. Write an expression that checks if given point (x, y) is within a circle K(O, 5).
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Exercises (2)7. Write an expression that checks if
given positive integer number n (n ≤ 100) is prime. E.g. 37 is prime.
8. Write an expression that calculates trapezoid's area by given sides a and b and height h.
9. Write an expression that checks for given point (x, y) if it is within the circle K( (1,1), 3) and out of the rectangle R(top=1, left=-1, width=6, height=2).
10.Write a boolean expression that returns if the bit at position p (counting from 0) in a given integer number v has value of 1. Example: v=5; p=1 false.
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Exercises (3)11. Write an expression that extracts from
a given integer i the value of a given bit number b. Example: i=5; b=2 value=1.
12.We are given integer number n, value v (v=0 or 1) and a position p. Write a sequence of operators that modifies n to hold the value v at the position p from the binary representation of n.
Example: n = 5 (00000101), p=3, v=1 13 (00001101)
n = 5 (00000101), p=2, v=0 1 (00000001)
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Exercises (4)13. Write a program that exchanges bits 3,
4 and 5 with bits 24, 25 and 26 of given 32-bit unsigned integer.
14. * Write a program that exchanges bits {p, p+1, …, p+k-1) with bits {q, q+1, …, q+k-1} of given 32-bit unsigned integer.
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