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Comment by williamvds | Hacker News Reader

From a C/C++ programmer's POV those may look like GOTO labels, I agree. The proposed syntax is probably a consequence of a modern trend in using := for declaration and assignment.

    x := 5

Where you can optionally insert the type between the colon and equals, otherwise it is deduced

    x : int = 5

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It's not modern at all. Type system notation has been using x : T to say "x has type T" for at least 50 years. It's the standard in academia, and has existed in real-world programming languages since 1971. [0]

[0] https://cstheory.stackexchange.com/questions/43971/why-colon...

It is an old idea and also a modern trend. Trends come and go. It is currently trendy.

90s fashion is also trendy right now. Which is great because a few years ago it was 80. The cycle continues!

"Currently trendy" how? Scala and Kotlin, to name just a few established programming languages, use the ": type" suffix style. They are neither "recent" nor from the original Algol era.

It depends on how you define "current", I suppose, but personally I'd consider Kotlin to be fairly recent.

Well, Kotlin is from 2011 and Scala from 2004! 11 and 18 years ago, respectively. I'd say neither is recent by any reasonable sense of the word that would imply their syntax or conventions are "a current trend".

11 years is not all that much for a PL, especially if you count from the date it was first announced, rather than from the first stable release (which for Kotlin was in 2016). For example, Rust started in 2006, and Rust 1.0 was in 2014, so it's actually older the Kotlin - but I think it still qualifies as "new", and many still consider it not fully battle-tested.

For another example, Python goes all the way back to 1991, with v1.0 in 1994. But it didn't really start to trend until early 00s.

> "11 years is not all that much for a PL"

Sure, if we redefine "recent" or "current" we can twist words to reach whatever conclusion. In reality, this ": type" syntax is neither new nor recent, nor is it "a current trend". Kotlin is also not recent. A decade is a lot.

You conveniently left Scala out, I suppose because it didn't fit your argument.

> "For another example, Python goes all the way back to 1991"

Well, since we are discussing Python, the syntax for its type hints looks like what exactly? And it was discussed as far back as 2014. Is that "recent"?

If you look at the thread, I'm not the same person who originally made the claim.

Nevertheless, it is definitely the case that the "name: type" syntax is noticeably more trendy now than it was, say, 15 years ago. Sure, there were plenty of languages that had it already back then, including Scala (and ML, and Delphi, and ...). But how many of them were mainstream? Whereas now, this syntax is embraced by Python and TypeScript.

And not even OP claimed that the syntax itself is new or recent; I mean, everybody who knows about Pascal knows how old it really is! They literally said "it's an old idea" that is "currently trendy".

I used to code for a language called "Spad" — originally shipped in 1972(?). The syntax:

    x : t = e

Was called "headform" and was the only syntactic form for the whole language. (Expressions used a shunting yard algorithm to desugar into a sequence of headform.)

The language included modules, classes, parameterics, functions, constraints, ..., whatever.

Well, everything looks like a pile of dirt when the only tool you have is a Spad.

ducks

> The proposed syntax is probably a consequence of a modern trend...

ML uses `name: type = value`. It came out over a decade before C++ and just one year after C.

In English, the colon is used to separate a term to its definition, so it looks perfectly apt to mark declarations.

Besides, it makes it trivial for text editors to implement "go to definition", and many other niceties without a real semantic parser.

I don't think this has anything to do with modern trends - := is a formal way of writing assignment (the widely used = is actually an equality sign), and has already been present in Pascal for decades (and other languages as well).

https://en.wikipedia.org/wiki/ALGOL_58

ALGOL, the := in programming languages used for assignment comes from IAL which became ALGOL 58. It's definitely not a modern development. Go reintroduced it to popular mainstream languages, sort of. Except they still use = for assignment and := is used when it's also declaring a new variable.

:= for assignment ultimately comes from math, as do most operators in early Algol: https://www.masswerk.at/algol60/report.htm#2_3

All the replies are missing something, does cpp2 have goto labels? What happened to them.

Unless you now have named loops in modern C++ now this removing goto is problematic.

I’m not sure I’d := is a “modern trend.” Smalltalk had it circa 1972, but none of the modern-day hip languages I can think of do. Your latter example is a common syntax, but the colon is omitted with the type in most languages (TypeScript, Rust, etc.).

X being a modern trend does not mean it was not done in the past. It doesn't mean that it hasn't trended in the past either.

So what does it mean then?

It was done in the very distant past. It was done in the intervening time. And it's done now. "Modern" trend?

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