applied object oriented programming › slides › 02.pdf · operator overload vu, mif, programų...

Applied object orientedprogramming

Operators and type systems

Today

• .NET history

• Operators in .NET

• Loops

• Type systems

.NET history

VU, MIF, Programų sistemų katedra

Code "conversion"


.NET Core

• Cross-platform .NET development platform

• Runs on windows/macOS/linux

• Open source https://github.com/dotnet/core

• Languages that can be used with: C#, F# and VB

• Still new*, so it is changing a lot

• .NET Core 3.0 is scheduled for September 2019

* RC released late 2015, stable – mid 2016


https://github.com/dotnet/core

.NET Core vs .NET.NET .NET Core

Cross-platform - +

Windows forms + + (only Win)

WCF services + -

WPF + + (only Win)

Lightweight with containers

- +


Which framework should you choose?

• Depends on your needs:• Is it important for you to have cross-platform application?

• Do you want to use containers

• Depends on available external packages:• Before choosing framework – do analysis on existing packages that you will

need to use for assignments.

• Course recommendation: .NET framework + .NET Core framework


Arithmetic operators

• A = 10; B = 20


Comparison operators


Logical operators

• Short-circuit evaluation: look in and.csA = True, B = False


Binary operators (1)

• A = 0011 1100

• B = 0000 1101

• -----------------

• A&B = 0000 1100

• A|B = 0011 1101

• A^B = 0011 0001

• ~A = 1100 0011


Binary operators (2)

• A = 60 (0011 1100), B = 13 (0000 1101)


Assignment operators


Syntax sugar• Syntax sugar

• Simple as +=

• Get/Set changed to property

• Type inference, as example.

• Syntax salt• „break“ usage inside „switch“

• When hiding inherited method, must use „new“

• Designed to prevent one from writing bad code


Syntactic saccharin

• Gratuitous syntax that does not make programming any sweater :)


var• int i = 10;

• Explicit definition

• var i = 10;• Implicit definition

• Implicit type can be:• int, bool, etc.

• Anonymous type

• User defined type

• .NET class


Ternary operator

• condition ? value if true : value if false


Operator overload


• Word „operator“ and the operator sign.

• Specific heading (look operatorOverload.cs)

• More on: Overloadable Operators, MSDN

public static Box operator +(Box b, Box c)

Operator Description

+, -, !, ~, ++, --, true, false Can be overloaded (unary)

+, -, *, /, %, &, |, ^, <<, >> Can be overloaded (binary)

==, !=, <, >, <=, >= Can be overloaded

&&, || Cannot do it simple way

+=, -=, *=, /=, %=, &=, |=, ^=, <<=, >>= Cannot do it simple way

=, ., ?:, ??, ->, =>, f(x), as, checked, unchecked,

default, delegate, is, new, sizeof, typeofCannot do it

Null-coalescing operator

Answer = Answer1 ?? Answer2 ?? Answer3 ?? Answer4;

Syntactic sugar:


switch• int and string types (before c# 8)

• Break is a must:


switch expressions (c# 8)

Switch expressions (c# 8) (2)

• Property pattern – switch to filter on specific property;

• Tuple pattern – switch to filter on more than one property;

• Positional pattern – using deconstruct

• More to read - https://docs.microsoft.com/en-us/dotnet/csharp/whats-new/csharp-8#switch-expressions

https://docs.microsoft.com/en-us/dotnet/csharp/whats-new/csharp-8#switch-expressions

Cycles: for and foreach


While and do-while


Types• Value types

• Reference types

• Pointer types


Demo time

Types• Ref vs value


Value types

• Enumerations

• Structs (all below „under the hood“ is struct):• Numeric types

• Integral types

• Floating-point types

• decimal

• bool

• User defined structs


http://msdn.microsoft.com/en-us/library/sbbt4032.aspx

http://msdn.microsoft.com/en-us/library/ah19swz4.aspx

http://msdn.microsoft.com/en-us/library/exx3b86w.aspx

http://msdn.microsoft.com/en-us/library/9ahet949.aspx

http://msdn.microsoft.com/en-us/library/364x0z75.aspx

http://msdn.microsoft.com/en-us/library/c8f5xwh7.aspx

Value types


Value types

• GetType:


Formating numeric typesSymbol Definition Example Result

C or c Currency Console.Write("{0:C}", 2.5);

Console.Write("{0:C}", -2.5);

$2.50

($2.50)

D or d Decimal Console.Write("{0:D5}", 25); 00025

E or e Scientific Console.Write("{0:E}",

250000);

2.500000E+005

F or f Fixed-point Console.Write("{0:F2}", 25);

Console.Write("{0:F0}", 25);

25.00

25

G or g General Console.Write("{0:G}", 2.5); 2.5

N or n Number Console.Write("{0:N}",

2500000);

2,500,000.00

X or x Hexadecimal Console.Write("{0:X}", 250);

Console.Write("{0:X}", 0xffff);

FA

FFFF


Type system


Enum

• Value type, an enumeration, a distinct type that consists of a set ofnamed constants called the enumerator list

• Has:• Name,

• Hidden integer type• e.g. Byte, Int32 ar UInt64,

• A set of fields


• Cannot:

– Have methods

– Implement interfaces

– Define properties orevents

– Be generic

http://msdn.microsoft.com/en-us/library/system.byte(v=vs.110).aspx

http://msdn.microsoft.com/en-us/library/system.int32(v=vs.110).aspx

http://msdn.microsoft.com/en-us/library/system.uint64(v=vs.110).aspx

Enum


Enum

• Hidden type – int

• Starts with 0:

• Another way:

• Look:• enum2.cs


Enum


Struct• Value type

• Defines:• Data

• Operations on data

• Possible to do:• Create an instance

• Pass them as parameters

• Save as local types

• Have it as a field inside both – reference and value types

• Struct can implement and interface.


Struct

• Has:• Fields

• Methods (incl. Constructor)

• Properties

• Operators

• Events

• Delegates.


Struct: diff from class• Value vs reference

• Struct cannot be null

• Class is to be used for larger objects.

• Classes can be inherited, structs - cannot.

• Struct does not have destructor

• Struct cannot be abstract

• In struct you can override only these:• Equals()

• GetHashCode()

• GetType()

• ToString() – look operatorOverload.cs


Struct: diff from class• Events in classes are automatically locked and thread-safe,

while in structs - not thread-safe.

• Struct cannot have volatile

• Sizeof does not work with classes

• Field inicialization inside:


Instructs compiler not to change (optimize)

assigments of variables

Struct: diff from class

• Struct cannot have not empty constructor without params

• Static constructor works only with classes, look. struct3. cs

• Equals is behaving differently. Struct4.cs

For more:

-property.cs

-book.cs


Literature

• Basics:

• MCSD sertification toolkit: second chapter, ahalf of the third chapter

• MSDN: Operator Overloading Tutorial

• Extra: nullable types (highly recommended!)

• http://msdn.microsoft.com/en-us/library/2cf62fcy.aspx

• http://msdn.microsoft.com/en-us/library/1t3y8s4s.aspx

• Extra-extra:

• Decimal floating point in .NET. C# in Depth. (on web).


http://msdn.microsoft.com/en-us/library/2cf62fcy.aspx

http://msdn.microsoft.com/en-us/library/1t3y8s4s.aspx

Next time

• Guests – last year best team will present their application!

• Three main OOP pillars:• Encapsulation

• Inheritance

• Polymorphism

• Demo of creating a web service using .Net Core

• Guests - GIT

Questions


applied object oriented programming › slides › 02.pdf · operator overload vu, mif, programų...

Documents