Wikipedia

Comparison of programming languages by type system

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This is a comparison of the features of the type systems and type checking of multiple programming languages.

Brief definitions

  • A nominal type system means that the language decides whether types are compatible and/or equivalent based on explicit declarations and names.
  • A structural type system means that the language decides whether types are compatible and/or equivalent based on the definition and characteristics of the types.
  • Type checking determines whether and when types are verified. Static checking means that type errors are reported based on a program's text (source code). Dynamic checking means that type errors are reported based on a program's dynamic (run-time) behavior.
Language Type safety Type expression Type compatibility and equivalence Type checking
A+ strong dynamic
ActionScript 3.0 strong implicit with optional explicit typing static
ABC strong
ABAP strong nominal static
Ada strong[TS 1] explicit nominal static
Agda strong nominal static
Aldor weak partially implicit[1] static
Alef strong static
ALGOL 58 strong explicit static
ALGOL 60 strong explicit static
ALGOL 68 strong explicit structural static & tagged unions
ALGOL W strong static
Alice strong implicit with optional explicit static
Alma-0 static
AmbientTalk strong dynamic
AMOS BASIC static
AngelScript strong static
APL strong dynamic
AppleScript weak dynamic
Arc dynamic
Assembly ? ? ? ?
AutoHotkey typeless — — —
AutoLISP dynamic
Ateji PX strong explicit nominal static
AWK weak implicit dynamic
B typeless
Ballerina strong structural static
Bash ? ? ? ?
BASIC strong explicit nominal static
BCPL typeless
BeanShell strong nominal dynamic
BLISS typeless — — —
Boo strong implicit with optional explicit typing static with optional dynamic typing
Bro strong implicit with optional explicit typing nominal static
C weak explicit nominal static
C-- weak static
C++ (ISO/IEC 14882) weak explicit with optional implicit typing (by using auto in C++11) nominal static[TS 2]
C* weak explicit static
C# weak[TS 3] implicit with optional explicit typing nominal static[TS 4]
C shell ? ? ? ?
Caml strong implicit with optional explicit typing static
Cecil dynamic with optional static typing
Clean strong implicit static
Ceylon strong static
Chapel implicit with optional explicit typing static
CHILL strong static
ChucK strong
Cilk weak explicit static
Claire strong implicit with optional explicit typing dynamic with optional static typing
Clean strong ?
Clojure strong implicit with optional explicit typing dynamic
CLU strong
COBOL strong explicit nominal static
Cobra strong explicit with optional implicit typing static with optional dynamic typing
CoffeeScript implicit dynamic
ColdFusion (CFML) strong implicit dynamic
COMAL strong
Common Lisp strong implicit with optional explicit typing structural for implicit typing, nominal for explicit typing dynamic, some static checking(depending on implementation)
Component Pascal strong static
Cool strong explicit static
CORAL strong static
Crystal implicit with optional explicit typing[2] structural static
Cuneiform explicit static
Curl strong nominal
Curry strong implicit with optional explicit typing static
Cython strong implicit with optional explicit typing nominal (extension types) and structural (Python) dynamic with optional static typing
D weak[TS 3] explicit nominal static
Dart strong[3] gradual typing nominal static with optional dynamic typing
Dylan strong dynamic
Eiffel strong nominal static
Elixir strong implicit dynamic
Erlang strong implicit dynamic
Euphoria strong explicit, implicit with objects nominal static, dynamic with objects
F# strong implicit nominal static
Forth typeless — — —
Fortran strong explicit[TS 5] nominal static
Gambas strong explicit nominal
GLBasic strong explicit. Non-explicit declarations available through project options nominal static
Gleam strong implicit with optional explicit nominal static
Go[4] strong partially implicit (local type inference) structural static
Gosu strong partially implicit (local type inference) nominal (subclassing) and structural static
Groovy strong implicit with optional explicit typing dynamic with optional static typing
Harbour strong implicit with optional explicit typing dynamic
Haskell strong implicit with optional explicit typing nominal[5][6] static
Haxe strong implicit with optional explicit typing nominal (subclassing) and structural static with optional dynamic typing
Io strong implicit dynamic
icon strong implicit dynamic
ISLISP strong dynamic
J strong dynamic
Java strong[7] explicit nominal static
JavaScript weak implicit — dynamic
Julia strong implicit with optional explicit typing[8] structural for implicit typing, nominal for explicit typing dynamic
Joy strong dynamic
Kotlin strong partially implicit (local type inference) nominal static
LabVIEW strong
Lua strong implicit dynamic
Maple strong dynamic
Mercury strong static
Mathematica strong dynamic
MATLAB M-code strong dynamic
Modula-2 weak[TS 3] explicit nominal static
Modula-3 weak[TS 3] explicit structural static
MUMPS (M) typeless — — —
Neko dynamic
Nemerle strong implicit nominal static
NetLogo strong implicit dynamic
NetRexx strong implicit with optional explicit dynamic with optional static typing
newLisp implicit dynamic
NEWP strong static
Newspeak dynamic
NewtonScript dynamic
Nial dynamic
Nim strong partially implicit (type inference) static
Nickle strong
Nu dynamic
Oberon strong explicit nominal static and partially dynamic[TS 6]
Objective-C strong explicit nominal dynamic with optional static typing[9]
OCaml strong implicit with optional explicit typing nominal for records,[10] structural for objects[6][11] static
Object Pascal strong explicit nominal static
Opa strong implicit with optional explicit typing structural static
Oxygene weak implicit static
Oz-Mozart strong implicit structural dynamic
Pascal weak[TS 3] explicit nominal static
Perl 5 implicit dynamic
PHP weak implicit with optional explicit typing nominal dynamic
Plus strong explicit structural static, dynamic (optional)
Prolog dynamic
Pure dynamic
PureScript strong implicit with optional explicit typing nominal static
Python strong implicit (with optional explicit typing as of 3.5) nominal dynamic
R implicit dynamic
Raku partially implicit[TS 7] dynamic with optional static typing
REBOL strong implicit dynamic
Rexx typeless —, implicit wrt numbers — static+dynamic wrt numbers
RPG weak static
Ruby strong implicit — dynamic
Rust strong explicit with optional implicit typing[12] mostly nominal static
S dynamic
S-Lang strong implicit dynamic
Scala strong partially implicit (local type inference) nominal (subclassing) and structural static
Scheme strong implicit dynamic (latent)
Seed7 strong explicit nominal static
Simula strong static[TS 8]
Smalltalk strong implicit dynamic
Swift strong partially implicit (local type inference) nominal (subclassing) and structural static
Standard ML strong implicit with optional explicit typing structural static
Tcl dynamic
TypeScript ? optional structural static
Unicon strong implicit dynamic
Visual Basic strong implicit with optional explicit typing nominal static
Visual Basic (.NET) weak[TS 3] explicit static
Visual Prolog strong partially implicit nominal static
Wolfram Language strong dynamic
Windows PowerShell strong implicit dynamic
XL strong nominal static
Xojo strong explicit nominal static
XPath/XQuery strong partially implicit nominal dynamic with optional static typing
Language Type safety Type expression Type compatibility and equivalence Type checking

Notes

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  1. ^ Unsafe operations are well isolated by a "Unchecked_" prefix.
  2. ^ with optional dynamic type casting (see dynamic cast)
  3. ^ a b c d e f It is almost safe, unsafe features are not commonly used.
  4. ^ with optional dynamic type (see dynamic member lookup)
  5. ^ Optionally, typing can be explicitly implied by the first letter of the identifier (known as implicit typing within the Fortran community).
  6. ^ dynamic checking of type extensions i.e. inherited types
  7. ^ explicit for static types
  8. ^ optional for formal and virtual procedures

References

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  1. ^ Aldor User Guide (PDF). Aldor.org. 2002. pp. 40, 61. Retrieved 3 June 2021.
  2. ^ "Type Inference Crystal". Crystal Language Reference. Retrieved 3 June 2021.
  3. ^ "The Dart type system". dart.dev. Retrieved 2020-04-08.
  4. ^ The Go Programming Language Specification
  5. ^ Löh, Andres. "Why does Haskell not have records with structural typing?". Stack Overflow. Archived from the original on 2016-03-14. Retrieved 2020-04-13.
  6. ^ a b King, Alexis (2020-01-19). "No, dynamic type systems are not inherently more open". lexi-lambda.github.io. Archived from the original on 2020-03-01. Retrieved 2020-04-13.
  7. ^ Sheng Liang, Gilad Bracha. Dynamic class loading in the Java virtual machine. Volume 33, Issue 10 of ACM SIGPLAN Notices, October 1998.
  8. ^ "Types · the Julia Language". Archived from the original on 2018-07-24. Retrieved 2018-07-24.
  9. ^ Developer.apple.com Archived June 10, 2009, at the Wayback Machine
  10. ^ "Record · Reason". reasonml.github.io. Archived from the original on 2020-03-31. Retrieved 2020-04-13.
  11. ^ "Structural type system", Wikipedia, 2019-03-29, retrieved 2020-04-13
  12. ^ "rust-lang/rustc-dev-guide". GitHub. Retrieved 2020-04-08.
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