Comparison of Programming Languages - Type Systems

Type Systems

Brief definitions

  • Compatibility among composite types describes the behavior of functions applied to data typed similarly to its intended type. Name-based compatibility means that functions work only on data of its intended type and declared subtypes. Property-based compatibility means that functions work on any data that has the same properties as its intended type.
  • Type checking determines whether and when types are verified. Static checking occurs at compile-time. Dynamic checking occurs at run-time.
Language Type strength Type safety Type expression Type compatibility among composites Type checking
ActionScript 3.0 strong safe implicit with optional explicit typing static
Ada strong safe explicit name-based partially dynamic
Aldor strong unsafe implicit static
ALGOL 58 strong safe explicit static
ALGOL 60 strong safe explicit static
ALGOL 68 strong safe explicit property-based static
APL strong safe dynamic
AutoHotkey none
Ateji PX strong safe explicit name-based static
BASIC varies by dialect
BLISS none n/a n/a n/a n/a
BeanShell strong safe name-based dynamic
Boo strong safe implicit with optional explicit typing static with optional dynamic typing
C weak unsafe explicit name-based static
C++ (ISO/IEC 14882) strong unsafe explicit name-based static
C# strong safe implicit with optional explicit typing name-based static
Clean strong safe implicit static
Clojure strong safe implicit with optional explicit typing dynamic
COBOL strong static
ColdFusion (CFML) strong safe implicit dynamic
Common Lisp strong safe implicit with optional explicit typing dynamic
Curl strong safe name-based
Cython strong safe implicit with optional explicit typing name-based (extension types) and property-based (Python) dynamic with optional static typing
D strong unsafe explicit name-based static
Dylan strong safe dynamic
Eiffel strong safe name-based static
Erlang strong safe implicit dynamic
Euphoria strong safe explicit, implicit with objects name-based static, dynamic with objects
F# strong safe implicit name-based static
Falcon strong safe implicit property-based dynamic
Forth none n/a n/a n/a n/a
Fortran strong safe explicit name-based static
Gambas strong safe explicit name-based
GLBasic strong safe explicit. Non-explicit declarations available through project options name-based static
Go strong safe implicit with optional explicit typing property-based static
Gosu strong safe partially implicit (local type inference) name-based (subclassing) and property-based (structural) static
GraphTalk weak
Groovy strong safe implicit with optional explicit typing dynamic with optional static typing
Harbour strong safe implicit with optional explicit typing dynamic
Haskell strong safe implicit with optional explicit typing property-based static
haXe strong safe implicit with optional explicit typing name-based (subclassing) and property-based (structural) static with optional dynamic typing
Io strong safe implicit dynamic
ISLISP strong safe dynamic
J strong safe dynamic
Java strong safe explicit name-based static
JavaScript weak implicit dynamic
Joy strong safe dynamic
Lua weak safe implicit dynamic
Mathematica strong dynamic
MATLAB M-code dynamic
Modula-2 strong unsafe explicit name-based static
Modula-3 strong unsafe explicit property-based static
Oberon strong safe explicit name-based static and partially dynamic
Objective-C weak safe explicit name-based (subclassing) and property-based (protocols) dynamic with optional static typing
OCaml strong safe implicit with optional explicit typing property-based static
Object Pascal (Delphi) strong safe explicit name-based static
Opa strong safe implicit with optional explicit typing property-based static
Oxygene strong unsafe implicit static
Oz strong safe implicit property-based dynamic
Pascal strong unsafe explicit name-based static
Perl 5 weak implicit dynamic
Perl 6 partially implicit dynamic with optional static typing
PHP weak implicit dynamic
Plus strong safe explicit property-based static, dynamic (optional)
Prolog strong dynamic
Pure dynamic
Python strong safe implicit property-based dynamic
REBOL strong safe implicit dynamic
RPG (IBM) strong unsafe static
Ruby strong safe implicit property-based dynamic
Rust strong safe implicit with optional explicit typing static with optional dynamic typing
S strong dynamic
S-Lang strong safe implicit dynamic
Scala strong safe partially implicit (local type inference) name-based (subclassing) and property-based (structural) static
Scheme strong implicit dynamic (latent)
Simula strong safe static
Smalltalk strong safe implicit dynamic
Standard ML strong safe implicit with optional explicit typing property-based static
Tcl dynamic
Visual Basic strong safe implicit with optional explicit typing name-based static
Visual Basic .NET strong unsafe explicit static
Visual Prolog strong safe partially implicit name-based static
Windows PowerShell strong safe implicit dynamic
XL strong safe name-based static
Language Type strength Type safety Type expression Type compatibility among composites Type checking

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