Type alias
A type alias is a declaration that gives an existing type an alternative name without creating a distinct type or representation.
Essential TypeScript 5, Third Edition
A type alias is a named TypeScript type definition that can represent an existing type or a composed type.
- How it is used
- Names reusable type definitions to reduce duplication in function signatures, object shapes, and application data schemas.
- How deep it goes
- Defines the syntax and works through several applications, while noting that an alias does not change compiler treatment.
- Examples
- Uses item counts, product arrays, city strings, a Lowdb task schema, and objects created by a constructor function.
- What you can do after
- Apply it via TypeScript annotations and assertions to reuse type definitions and check shaped application data.
Read how Essential TypeScript 5, Third Edition explains type alias →
Go in Action, Second Edition
A type alias gives an existing type an alternate name without creating a distinct type.
- How it is used
- Gives an existing type a context-specific name while keeping its values interchangeable with the original type.
- How deep it goes
- Defines `type A = B` and contrasts compiler behavior and methods with defined types; does not develop a larger alias implementation.
- Examples
- Uses byte and rune as built-in aliases, then contrasts an illustrative measurement alias with a distinct Magnitude type.
- What you can do after
- Evaluate/understand when an alternate name suffices and when a distinct type provides compiler-enforced separation or methods.
Learn Haskell by Example
A type synonym gives an existing type an alternate name without creating a distinct representation or type identity.
- How it is used
- Clarifies the intended role of ordinary representations such as character lists, filenames, and strings.
- How deep it goes
- Defines aliases, demonstrates interchangeability, and stops short of creating a distinct type identity.
- Examples
- Uses Alphabet for cipher alphabets, FilePath for command-line filenames, and GHCi commands for inspection.
- What you can do after
- Apply type synonyms in Haskell code and inspect their resulting values and signatures through GHCi.
Kotlin in Action, 2E
A type alias is a Kotlin declaration that gives an alternative name to an existing type without creating a distinct type.
- How it is used
- Improves readability by naming long generic or functional types without changing how those types behave.
- How deep it goes
- Explains declaration syntax, usage, tradeoffs, and compile-time expansion, but stops short of adding type safety.
- Examples
- Uses the NameCombiner functional alias and contrasts a ValidatedInput alias with a value class.
- What you can do after
- Apply it by naming repeated complex types while recognizing when a distinct value class is required for stronger type separation.
Learn C++ by Example
A type alias is a declaration that gives an existing type an alternative name.
- How it is used
- Defines a readable name for a custom std::chrono duration used in practical time conversions.
- How deep it goes
- Defines the using form through a century-duration example and defers broader details about using to later coverage.
- Examples
- Uses a centuries alias to represent two hundred years and convert that duration into seconds, hours, and days.
- What you can do after
- Build it from scratch by naming a parameterized chrono duration with using and applying the alias in conversions.
Modern C
A type alias is an alternative name for an existing C type that does not create a distinct type.
- How it is used
- Introduces readable names for existing C types, especially structures and arrays.
- How deep it goes
- Explains alias identity, structure forward declarations, array syntax, and _t reservation rules.
- Examples
- Uses multidimensional double arrays, staged array aliases, structure declarations, and size_t as examples.
- What you can do after
- Apply it via typedef to name existing structures, arrays, and other C types without changing their identities.
Related concepts
- typedefproduced by · typedef is a C and C++ declaration mechanism that introduces an alternative name for an existing type.
- newtype idiomcontrasts with · The newtype idiom defines a distinct type by wrapping an existing type, typically preserving its representation while enabling type-specific distinctions or behavior.
- atomic typeequivalent to · An atomic type is a type whose supported accesses and operations are indivisible with respect to concurrent execution and provide defined synchronization semantics.
- jmp_bufincludes · jmp_buf is an opaque C library-defined type representing a saved execution environment for setjmp and longjmp.
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