Does “untyped” also mean “dynamically typed” in the academic CS world?

Question

I\'m reading a slide deck that states \"JavaScript is untyped.\" This contradicted what I thought to be true so I started digging to try and learn more.

Every answer

Answer 1

I've looked into it, and found that the answer to your question is simply, and surprisingly, "yes": academic CS types, or at least some of them, do use "untyped" to mean "dynamically typed". For example, Programming Languages: Principles and Practices, Third Edition (by Kenneth C. Louden and Kenneth A. Lambert, published 2012) says this:

Languages without static type systems are usually called untyped languages (or dynamically typed languages). Such languages include Scheme and other dialects of Lisp, Smalltalk, and most scripting languages such as Perl, Python, and Ruby. Note, however, that an untyped language does not necessarily allow programs to corrupt data—this just means that all safety checking is performed at execution time. […]

[link] (note: bolding in original) and goes on to use "untyped" in just this way.

I find this surprising (for much the same reasons that afrischke and Adam Mihalcin give), but there you are. :-)

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Edited to add: You can find more examples by plugging "untyped languages" into Google Book Search. For example:

[…] This is the primary information-hiding mechanism is many untyped languages. For instance PLT Scheme [4] uses generative structs, […]

— Jacob Matthews and Amal Ahmed, 2008 [link]

[…], we present a binding-time analysis for an untyped functional language […]. […] It has been implemented and is used in a partial evaluator for a side-effect free dialect of Scheme. The analysis is general enough, however, to be valid for non-strict typed functional languages such as Haskell. […]

— Charles Consel, 1990 [link]

By the way, my impression, after looking through these search results, is that if a researcher writes of an "untyped" functional language, (s)he very likely does consider it to be "untyped" in the same sense as the untyped lambda calculus that Adam Mihalcin mentions. At least, several researchers mention Scheme and the lambda calculus in the same breath.

What the search doesn't say, of course, is whether there are researchers who reject this identification, and don't consider these languages to be "untyped". Well, I did find this:

I then realized that there is really no circularity, because dynamically typed languages are not untyped languages — it's just that the types are not usually immediately obvious from the program text.

— someone (I can't tell who), 1998 [link]

but obviously most people who reject this identification wouldn't feel a need to explicitly say so.