Clojure.core: Batteries Almost Included

[michaelochurch]

http://adambard.com/blog/clojure-batteries-included/

[jared314]

Why did the author mention core.typed, but leave out core.contracts?

https://github.com/clojure/core.contracts

[adambard → jared314]

I started writing a bit on contracts, but it was 2am and I really wanted to be done. (I thought I had a little more time between then and HN front page.) You're right, though, I should at least give it a shout and let people know about it.

[adambard → jared314]

There is now a (mildly half-assed) blurb on contracts, not that fogus was likely to feel left out otherwise.

[fhd2]

Nice writeup, wish this existed back when I worked with Clojure. The migration away from clojure.contrib caused quite the mess. Back then (about a year ago), looking for a function you want (things you would expect in the standard library) was like this:

00:05 Found it in clojure.contrib

01:05 Figured out which standalone library it has moved to (or conclude that it has disappeared)

01:15 Figured artefact/group ID and current version out

That was a bit annoying.

[trothoun]

The core.match example uses python-style triple quotes. Is that actually possible in clojure? I would be enormously excited if it is.

[omaranto → trothoun]

I don't think clojure has triple-quoted strings. Something like

    """
    a
    """

parses as three strings, two of which are empty: "", "\na\n", and "". (Clojure strings are allowed to contain literal newlines.)

[adambard → omaranto]

Hah, so it is. It was pretty late when I finished this one off, sorry about that.

[tobik → trothoun]

why? in clojure strings can be multiline already. so there is no point in triple quotes.

[drcode → tobik]

So you don't have to escape internal quotes.

[michaelochurch → tobik]

Triple quotes tend to come up for two purposes:

1. Long regular expression strings that have quote marks involved. I'm not a fan of large, complex regexes, but a lot of people dislike the line-noise added by escaping.

2. Docstrings that may have quotes in them.

It's to remove the string escaping that makes literals look different from the strings they describe.

[tobik → michaelochurch]

Thanks.

Thinking about it, I guess triple-quoted strings also facilitate doctests involving strings that would otherwise be really awkward to read/write.

[adambard → trothoun]

No, it's not, my bad. Not that there's a need for them, as it turns out.

[michaelochurch → trothoun]

I tried it at a REPL in version 1.5.1 and it didn't work for me. I don't think standard Clojure has triple-quote strings.

[landhar]

I often find myself having to spend more time than necessary to track down how to add these libraries to the dependencies of my leiningen projects.

I think this post would be a lot more useful if it included a link to clojars for each one of these libraries.

[adambard → landhar]

I was thinking about including the Leiningen dependency line, but I don't want someone including the wrong version later because I didn't update it. Install info is usually pretty prominent on the github pages of the projects (which I've linked to).

[weavejester → landhar]

They're not on Clojars; the Maven repository they use is build.clojure.org. The project source code for all the contrib libraries is on Github at https://github.com/clojure

[landhar → weavejester]

Thanks for clarifying !

[tieTYT]

I still have no idea what core.unify does.

[adambard → tieTYT]

Give it two patterns with some unknowns and it tries to get values for the unknowns via pattern-matching. That's all it does! It's one of those things that humans do very well but computers have trouble with, so I'm afraid it doesn't look too impressive.

[tieTYT → adambard]

You mean like those problems that prolog is good at solving? Such as those describe here? http://dangoldin.com/2013/06/07/fun-with-prolog-priceonomics...

[adambard → tieTYT]

Cool, thanks!

[jared314 → tieTYT]

It is a subset of core.logic's functionality. It allows you to use unification in your code without the full logic engine of core.logic.

[tieTYT → jared314]

This comment assumes I know what core.logic does.

[jared314 → tieTYT]

True, but your comment gave no indication of context, your knowledge level of clojure, awareness of logic programming, or an actual question. So, I had no basis to give a response that answered the question you did not ask. I honestly thought you were just trolling.

[olenhad]

Quite an awesome whirlwind tour. Didn't know about core.unify, which seems quite impressive.

[adambard → olenhad]

I suspect core.logic is the more practical library in many cases. I wrote a disproportionate amount on core.unify because I couldn't find any official docs that approached it from the perspective of someone (e.g. me) who didn't already know all about Prolog and unification in general.