Talk:Dynamic programming language

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Archive 1

What exactly is a dynamic programming language ?[edit]

I believe that everyone agrees that dynamic programmig language does not have a precise definition. That's including programming language designers/designers wannabe [1]. In addition, this term has been greatly misused by journalists and techies (including Gosling) who simply didn't know what they were talking about. If this article provides a precise definition, well, we need to build it first.

I believe that everybody agrees that

  • Compiled C is not dynamic.
  • Lisp, Scheme, Dylan, Python, Ruby are dynamic.

What about

  • Haskell and OCaml ? After all, they support dynamic programming, with extensions, they can perform compile-time reflexivity, etc.
  • Java ? After all, it supports reflexivity and, with extensions, it supports dynamic programming, etc.
  • Acute ? It's statically + dynamically typed.
  • Self-modifiable assembly language ?


Criteria[edit]

  • Dynamic = interpreted ?
  • Dynamic = dynamically-typed ?
  • Dynamic = check as many things as possible at run-time rather than ahead-of-time (including types and possibly syntax) ?
  • Dynamic = no need for type annotations ?
  • Dynamic = interactive programming ?
  • Dynamic = modifying properties of the language itself at run-time ? (à la SmallTalk)
  • Dynamic = run-time read/only introspection ?
  • Dynamic = run-time read/write introspection ?
  • Dynamic = dynamically linked ?
  • Dynamic = new and shiny ?
  • Is there such a thing as a dynamic programming language or should we say that one language is more dynamic than another ? I would vote for the second option.
  • Is there such a thing as a dynamic programming language or should we say that one implementation of a language is dynamic ? I would vote for the second option. After all, iirc, there's an interpreted version of C, with a toplevel and the possibility of adding or replacing functions at run-time. Still, it is the same language.

I have a better suggestion: A dynamic programming language is one that supports rapid development cycles: rapid modification of code and designs, etc. Also, such languages are not "new and shiny"; they have been with us since the late 1950's (LISP).

Interpretation[edit]

Lisp is dynamic. Lisp can be compiled. Is that a good-enough counter-example ? I must admit that I don't know enough about the internals of Lisp compilation. Yoric 16:58, 14 June 2006 (UTC)

Lisp, Scheme, Dylan and lots of other "dynamic" languages are regularly compiled to assembly, C or other lower level presentation. IMHO the issue is not about compiling or interpreting, both of which are ambigous terms in themselves. TokenLander (talk) 17:48, 3 March 2010 (UTC)

Dynamic typing, type annotations[edit]

Could anyone give an example of a dynamic programming language which is not dynamically typed, or a dynamically typed programming language which is not dynamic? -- ciphergoth 20:05, 2005 Apr 5 (UTC)

Maybe. I'm still not sure what exactly this article wants to classify as a dynamic language. Pike is a statically typed, high level, object oriented, interpreted language. Is it a dynamic language? I can't tell from this article. Its similar to a statically typed python with C-style syntax though. Generic Player 04:09, 6 Apr 2005 (UTC)

Another example could be Typed Scheme, http://www.ccs.neu.edu/home/samth/typed-scheme/ , statically typed Scheme. Exact position of Scheme on the static-dynamic spectrum could be argued but it is usually lumped in the dynamic camp. TokenLander (talk) 18:12, 3 March 2010 (UTC)

This article is a complete mess, and badly in need of a rewrite. The language is informal and non-standard, and there are no sources to any of the potentially controversial (or at least non-obvious) assertions made. Plus, at least half of the content (the bit about functions and addresses) is simply incorrect. The way "dynamic" languages are described as using indirection rather than running code at a predefined memory address really is completely unimportant as a distinction -- it is possible to modify the contents of a memory address (or use it to point elsewhere) while code is running to change the behavior, and this can be done even in C. In fact, it is done in C quite often in some types of programming, such as emulators, for example.

The single most important distinguishing feature between most "dynamic" languages and "non-dynamic" languages has to do with type systems (and not interactivity, or some other fuzzily defined concept which doesn't hold under careful examination), yet type systems are practically ignored in the article. 70.36.30.117 06:27, 28 March 2006 (UTC)

simply because the type system is not the point. It may be easier to implement a dynamic language as a dynamically typed language. Still it is not the same. —Preceding unsigned comment added by 85.177.153.98 (talk) 13:53, 6 February 2008 (UTC)

I'm not sure about the dynamic typing part. I mean yes, every dynamic language I can think of is dynamically typed. But I believe that this absence of static or semi-static checks is more related to the fact that the designers of the language were not able to provide static checks, rather than a feature/drawback by itself. Yoric 14:25, 14 June 2006 (UTC)


To the best of my knowledge, no dynamic language needs type annotations -- although some can use them. Although OCaml is usually considered static by its fans and detractors, it doesn't need type annotations either. What do we conclude of this ? Yoric 16:58, 14 June 2006 (UTC)

Ocaml is statically typed, at compile time, and by most purposes very "static" language. I think we can conclude that the lack of visible type annotations doesn't make any difference when deciding how "dynamic" a language is. TokenLander (talk) 17:55, 3 March 2010 (UTC)

Characteristics of dynamic programming languages[edit]

The term dynamic programming language does not have a precise definition, but it is nevertheless useful to refer to what distinguishes "dynamic" languages such as Perl and Python from more traditional languages such as C, C++, and Java. Not all languages considered dynamic will have all of the features below, and some non-dynamic languages will share some of them or have some way to achieve the same effect; the reader should assume that there are exceptions nearly all of the generalizations below.

Traditional programming languages require that the program be annotated with extra information (such as type declarations) that makes the compile-time checking possible. Dynamic languages dispense with these annotations because they use extra information available at runtime instead. In particular, they are dynamically typed, and use automatic memory management.


The fact that people use the term dynamic programming language in a variety of imprecise ways doesn't mean it has no precise definition. The current definition "execute at runtime many common behaviors that other languages might perform during compilation" is correct. No language is entirely static (performing all behaviors at compile time) or entirely dynamic (performing all behaviors at runtime), most languages group in the center between the two extremes, with a few outliers ranking highly static (C) or highly dynamic (Smalltalk). That said, it is useful to classify languages based on which dynamic features they include, and how many dynamic features they include. A table similar to those on Comparison of programming languages would be useful on this page, showing at least "dynamic compilation" (eval/closures/continuations/higher-order functions/self-modification/just-in-time), "dynamic dispatch" (symbolic/multiple dispatch/polymorphic inline caching), "dynamic typing" (not to be confused with weak/implicit, since dynamic type systems can also be strong/explicit), "dynamic loading" (library extension/inclusion/linking), "introspection" (access to meta-information about the source/internal details of the runtime environment). Allisonrandal (talk) 21:24, 13 September 2009 (UTC)

Closures, continuations & HOFs have nothing to do with "dynamic compilation". And why are macros mentioned in the article? In most languages they are purely a compile time feature. —Preceding unsigned comment added by 130.234.5.137 (talk) 20:27, 25 February 2010 (UTC)

Closures are a way of creating new functions at runtime - in that sense they are related to dynamic compilation. Macros in Lisp can be seen as a run-time extension to the interpreter / compiler.

But closures don't create new code at runtime and thus have nothing to do with dynamic compilation. They only bind a function with an environment, something that can be (and often is) done with plain C. And lisp macros are expanded at compile time, as long as the application doesn't use any form of 'eval' at runtime (in most cases it's not needed and some implementations might not even have 'eval') macros are not used after compilation. TokenLander (talk) 19:46, 18 March 2011 (UTC)

Advantages[edit]

  • Dynamic programming languages are generally somewhat easier for newcomers to programming, in large part because they need not understand the system of annotations referred to above in order to write programs
  • This delay can be dramatically reduced almost to zero in practice however, for instance, the Objective-C programming language used a pre-loaded cache and a small bit of assembler code in order to reduce this overhead to a single operation.

That's a claim I've often heard. I've never seen anything to back it. Does anyone have any clue ?

Yoric 14:25, 14 June 2006 (UTC)

Rewrite[edit]

I just started this rewrite, but didn't have time to finish it. I leave the text here in the hope it's useful in a future version -- ciphergoth 20:05, 2005 Apr 5 (UTC)

In computer science, a dynamic programming language is a kind of programming language in which many tests to ensure that each computational step is valid are deferred until the operation is actually performed (at runtime) rather than taking place when the program is first prepared for execution (at compile time). They allow programs to change their structure as they run: functions may be introduced or removed, new classes of objects may be created, new modules may appear.

Wrong Languages[edit]

You can't have it both ways: either a language tries to do extensive compile-time checking, or it defers such checks until runtime. Eiffel advertises itself with all the wonderful things it does at compile time. As a result, it can't be a "dynamic language". In fact, Eiffel is the prototypical static language.

Agreed. Neither are Oberon and Objective Modula-2.

VB6 has it both ways. The type of a variable can be declared and the compiler checks the method calls at compile time. Or if the type is Object, then the type checking is defered to runtime when the underlying type is queried to see if it will respond to the method call. 86.10.80.92 (talk) 21:46, 2 July 2008 (UTC)

Scripting[edit]

When I read about DPLs, my first question is "how is this different from scripting?" The article needs to explore this — right now the word "scripting" doesn't even appear, even though common DPLs are more commonly called "scripting languages."

Even if the distinction is purely artificial (I suspect there's differing opinions on that!) it's an obvious thing to talk about.Isaac R (talk) 18:14, 26 June 2009 (UTC)

<verbiage-conversion type="DIPLOMATIC">This Article Could Be Better</verbiage-conversion>[edit]

I'll see if I can find the time to take a crack at this article. It's in rough shape.

I think that the problem here is that it tries to define Dynamic programming language as a first order categorization. As other commenters have stated, "Dynamic" is used to refer to a large collection of semantics of a programming language.

The term "dynamic programming language" is a rather loose term used to categorize a programming language that tends to have many dynamic features. Sometimes "dynamic programming language" is used as a comparator of two or more languages. For example: "Why are you using C when a more dynamic programming language such as Lisp seems a better choice?"

If I can find the time, I'll take a whack at it.

Neil Smithline (talk) 20:49, 4 June 2012 (UTC)