Scala, a functional language for the JVM and JavaScript runtime, has recently been upgraded to version 3.0 with a new type system, new language features, and a number of syntactic improvements. Thinkstock’s editor-in-chief described the upgrade as a “complete overhaul”.

Scala 3, released in production on May 14, has both JVM and JavaScript running mechanisms and is positioned as a library for building high-performance systems with access to the ecosystem. The Scala 3 documentation can be found here.

New language features in Scala 3:

  • In an implicit improvement to Scala 2, terms of use can be specified by type, freeing function signatures from the term variable names that are never explicitly mentioned.
  • A given instance

Allowing programmers to determine typical values for a type makes programming a type class more straightforward without giving away implementation details.

  • Extension methods

It is now built directly into the language for better error information and improved type reasoning. * The implicit Conversion has been redesigned to Conversion, an instance of the type class.

  • The context function feature makes context abstractions first-class citizens.
  • If an implicit parameter cannot be resolved by the compiler, an import recommendation is provided to resolve the problem.

Type system improvements in Scala 3:

  • Enums, or enumerations, were redesigned to blend well with case classes to form a new standard for expressing algebraic data types.
  • Opaque type aliases allow developers to hide implementation details without affecting performance.
  • Cross and union types can express type constraints outside the inheritance hierarchy.
  • Polymorphic function types can abstract functions that accept type parameters in addition to value parameters. * Type lambdas are type-level functions that can be passed as type arguments without the need for auxiliary type definitions.
  • Scala 3 supports matching on type, rather than encoding type-level calculations using implicit parsing.

Object-oriented programming features in Scala 3:

  • Attributes are closer to classes and can now accept parameters

, making them more powerful as tools for modular software decomposition.

  • Open classes

Requires the library designer to mark classes as open. * Practical qualities of realization behavior sometimes should not be part of the type of inference. In Scala 3, these traits can be marked as transparent, hiding inheritance from the user.

  • Explicit NULL moves NULL out of the type hierarchy to statically catch errors.

Scala 3 also provides metaprogramming tools, including compile-time operations, referenced code blocks, and the ability to reduce numbers and methods at compile timeAn inline function

Other syntax improvements in Scala 3:

  • Optional braces support a nonintrusive, indented sensitive programming style.
  • newKeywords are now optional.
  • Type-level wildcards from_Instead of? 。
  • Implicit and its syntax have been heavily modified.