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Scala
Scala's Type System: a tutorial
Published: 2012/04/01
Channel: Ben Hutchison
Data Types C# - common language runtime types, nominal storage allocation, and value range
Data Types C# - common language runtime types, nominal storage allocation, and value range
Published: 2014/09/26
Channel: Damien Kettle
Nerd³ Makes... Systems Nominal
Nerd³ Makes... Systems Nominal
Published: 2015/01/03
Channel: OfficialNerdCubed
Types of Accounts : Personal Account, Real Account, Nominal Account
Types of Accounts : Personal Account, Real Account, Nominal Account
Published: 2015/12/21
Channel: Online Accounts Tuition Classes
Sampling: Simple Random, Convenience, systematic, cluster, stratified - Statistics Help
Sampling: Simple Random, Convenience, systematic, cluster, stratified - Statistics Help
Published: 2012/03/14
Channel: Statistics Learning Centre
Statistics Lesson 1 - Types of Data
Statistics Lesson 1 - Types of Data
Published: 2014/11/10
Channel: Aubrie Holman
Floating vs. Fixed Exchange Rates- Macroeconomics 5.4
Floating vs. Fixed Exchange Rates- Macroeconomics 5.4
Published: 2014/11/11
Channel: ACDCLeadership
Real GDP and nominal GDP | GDP: Measuring national income | Macroeconomics | Khan Academy
Real GDP and nominal GDP | GDP: Measuring national income | Macroeconomics | Khan Academy
Published: 2012/02/10
Channel: Khan Academy
Types of Variables
Types of Variables
Published: 2010/07/06
Channel: statslectures
Identifying Thread Pitch & Size
Identifying Thread Pitch & Size
Published: 2012/02/22
Channel: swagelok
Tolerancing Basics: Calculating a Fit between and Cylinder and a Hole
Tolerancing Basics: Calculating a Fit between and Cylinder and a Hole
Published: 2014/05/24
Channel: Technical Drawing 101 with AutoCAD Channel
Systems of Government:  Unitary, Federal, and Confederal
Systems of Government: Unitary, Federal, and Confederal
Published: 2014/09/03
Channel: Brad Cartwright Economics
Money supply: M0, M1, and M2 | The monetary system | Macroeconomics | Khan Academy
Money supply: M0, M1, and M2 | The monetary system | Macroeconomics | Khan Academy
Published: 2012/03/23
Channel: Khan Academy
Type-Z.E.R.O. - All Systems Nominal
Type-Z.E.R.O. - All Systems Nominal
Published: 2013/02/03
Channel: Eric Normandin
Lecture - 10 Transmission Line Parameters
Lecture - 10 Transmission Line Parameters
Published: 2008/01/26
Channel: nptelhrd
What Is Personal Real And Nominal Account?
What Is Personal Real And Nominal Account?
Published: 2017/06/20
Channel: smART X-mas
What Is Personal Real And Nominal Account?
What Is Personal Real And Nominal Account?
Published: 2017/08/16
Channel: Liam Liam
Systems Nominal: I Cant Type!
Systems Nominal: I Cant Type!
Published: 2014/12/23
Channel: DeathAngelGaming
Parliamentary vs Presidential System of Government
Parliamentary vs Presidential System of Government
Published: 2014/09/25
Channel: Brad Cartwright Economics
Type-ZERO - All Systems Nominal (MechWarrior Online Tribute)
Type-ZERO - All Systems Nominal (MechWarrior Online Tribute)
Published: 2013/01/02
Channel: Eric Normandin
Day 02, Video 03 Part 1 Core C# - More About Data Types
Day 02, Video 03 Part 1 Core C# - More About Data Types
Published: 2010/12/09
Channel: Bob Tabor
First Normal Form | Database Management System
First Normal Form | Database Management System
Published: 2014/09/30
Channel: Techtud
Classification Of Assets/Types Of Assets And Types Of Liabilities
Classification Of Assets/Types Of Assets And Types Of Liabilities
Published: 2015/09/09
Channel: Edupedia World
Lecture - 26 Load Flow Studies
Lecture - 26 Load Flow Studies
Published: 2008/01/28
Channel: nptelhrd
22  Limit And Fit Terminology
22 Limit And Fit Terminology
Published: 2014/03/18
Channel: FITTER E LEARNING 9867241975
Type-Z.E.R.O. - All Systems Nominal (OCD-13001)
Type-Z.E.R.O. - All Systems Nominal (OCD-13001)
Published: 2013/02/01
Channel: Overdrive Canada
All Systems Nominal: Episode #6 - Retroactive
All Systems Nominal: Episode #6 - Retroactive
Published: 2014/11/04
Channel: NoGutsNoGalaxyTV
Advanced English Grammar: Noun Clauses
Advanced English Grammar: Noun Clauses
Published: 2016/07/12
Channel: English Lessons with Adam - Learn English with Adam [engVid]
Systems Nominal (Anything But)
Systems Nominal (Anything But)
Published: 2014/12/24
Channel: Kyoto-Moto
What Is An Example Of A Real Account?
What Is An Example Of A Real Account?
Published: 2017/08/15
Channel: Liam Liam
All Systems Nominal: CW Chapter 2
All Systems Nominal: CW Chapter 2
Published: 2015/04/15
Channel: NoGutsNoGalaxyTV
[MWO] All Systems Nominal
[MWO] All Systems Nominal
Published: 2012/11/09
Channel: John Garren
Types of bank account
Types of bank account
Published: 2016/12/13
Channel: DeltaStep
Journal Entry for [24 Transactions] Simple explanations :-by kauserwise
Journal Entry for [24 Transactions] Simple explanations :-by kauserwise
Published: 2015/05/30
Channel: Kauser Wise
SPSS for questionnaire analysis:  Correlation analysis
SPSS for questionnaire analysis: Correlation analysis
Published: 2013/12/24
Channel: Phil Chan
Which Is Nominal Account?
Which Is Nominal Account?
Published: 2017/08/16
Channel: Liam Liam
Logoster Plays: Systems Nominal
Logoster Plays: Systems Nominal
Published: 2014/12/24
Channel: TheGamingChannel
SPSS Questionnaire/Survey Data Entry - Part 1
SPSS Questionnaire/Survey Data Entry - Part 1
Published: 2014/04/21
Channel: Quantitative Specialists
Management Information Systems: Data and Databases
Management Information Systems: Data and Databases
Published: 2016/12/02
Channel: Luther Maddy
Data Collection: Understanding the Types of Data.
Data Collection: Understanding the Types of Data.
Published: 2013/04/24
Channel: VelactionVideos
systems nominal new hack 2015
systems nominal new hack 2015
Published: 2014/12/23
Channel: doobyplease
SQL Normalization - The Basics - 1st, 2nd, 3rd Normal Form Software Engineering Tutorial
SQL Normalization - The Basics - 1st, 2nd, 3rd Normal Form Software Engineering Tutorial
Published: 2011/10/25
Channel: Edward Kench
All Systems Nominal: Episode #3 - Equilibrium
All Systems Nominal: Episode #3 - Equilibrium
Published: 2013/03/31
Channel: NoGutsNoGalaxyTV
Nominal Full Pallet Two Strand Chain Conveyor
Nominal Full Pallet Two Strand Chain Conveyor
Published: 2016/01/05
Channel: LathrupConveyors
CS\M03\T04 - About the common language runtime
CS\M03\T04 - About the common language runtime
Published: 2012/02/19
Channel: Brett Maytom
Timothy Jones - Brand Objects for Nominal Typing - ECOOP 2015
Timothy Jones - Brand Objects for Nominal Typing - ECOOP 2015
Published: 2015/08/17
Channel: ECOOP !
Macroeconomics: Crash Course Economics #5
Macroeconomics: Crash Course Economics #5
Published: 2015/08/24
Channel: CrashCourse
Electronic compact starter Episode 4: Setting the nominal current HF range
Electronic compact starter Episode 4: Setting the nominal current HF range
Published: 2017/01/26
Channel: ABB Low voltage products
RMU fuse operating trip mechanism
RMU fuse operating trip mechanism
Published: 2015/12/13
Channel: RODALCO2007
Common Data Types
Common Data Types
Published: 2012/12/08
Channel: Alex Chapman
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WIKIPEDIA ARTICLE

From Wikipedia, the free encyclopedia
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In computer science, a nominal or nominative type system (or name-based type system) is a major class of type system, in which compatibility and equivalence of data types is determined by explicit declarations and/or the name of the types. Nominal systems are used to determine if types are equivalent, as well as if a type is a subtype of another. It contrasts with structural systems, where comparisons are based on the structure of the types in question and do not require explicit declarations.

Nominal typing[edit]

Nominal typing means that two variables are type-compatible if and only if their declarations name the same type. For example, in C, two struct types with different names in the same translation unit are never considered compatible, even if they have identical field declarations.

However, C also allows a typedef declaration, which introduces an alias for an existing type. These are merely syntactical and do not differentiate the type from its alias for the purpose of type checking. This feature, present in many languages, can result in a loss of type safety when (for example) the same primitive integer type is used in two semantically distinct ways. Haskell provides the C-style syntactic alias in the form of the type declaration, as well as the newtype declaration that does introduce a new, distinct type, isomorphic to an existing type.[1]

Nominal subtyping[edit]

In a similar fashion, nominal subtyping means that one type is a subtype of another if and only if it is explicitly declared to be so in its definition. Nominally-typed languages typically enforce the requirement that declared subtypes be structurally compatible (though Eiffel allows non-compatible subtypes to be declared). However, subtypes which are structurally compatible "by accident", but not declared as subtypes, are not considered to be subtypes.

C++, C#, Java, Objective-C, Delphi, Swift, and Rust all primarily use both nominal typing and nominal subtyping.

Some nominally-subtyped languages, such as Java and C#, allow classes to be declared final (or sealed in C# terminology), indicating that no further subtyping is permitted.

Comparison[edit]

Nominal typing is useful at preventing accidental type equivalence, which allows better type-safety than structural typing. The cost is a reduced flexibility, as, for example, nominal typing does not allow new super-types to be created without modification of the existing subtypes.

See also[edit]

Notes[edit]

References[edit]

External links[edit]

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