Comments on: New ErlSQL Feature: Lisp-style Operator Expansion

By: Yariv

Yariv — Thu, 31 Jan 2008 09:36:56 +0000

It is a bit late :) In designing this feature, I decided to follow Erlang’s convention of using tuples where the number of elements is fixed, and lists where it’s variable. I’m not too worried about the efficiency, and I recognize it may be a bit confusing to read, but if you remind yourself that think tuple = fixed and list = variable, it will be easier to digest.

By: Marcelo Cantos

Marcelo Cantos — Thu, 31 Jan 2008 07:49:20 +0000

Sorry, for coming late to the party, but it seems to me that mixing tuples and lists isn’t helping the cause. This can be remedied by converting every 2-tuple {A,B} to a list [A|B].

original: {where,{’=',[{'+',[a,b,c]},{’+',[d,e,f]}]}}}
pure lists: [where,'=',['+',a,b,c],['+',d,e,f]]

Still not on par with Lisp, but quite an improvement, I think. Also, if a 2-tuple is identical to a cons cell, the storage and computational efficiency could well be the same.

By: LoRd

LoRd — Sun, 25 Nov 2007 21:52:49 +0000

Hi Yariv,

I am really have a problem to write a SQL func for mnesia. Can you give me an SQL example for mnesia using GROUP BY statement.?

many thanks

By: Dennis

Dennis — Mon, 25 Sep 2006 16:39:44 +0000

What lisp syntax? :)

By: Yariv

Yariv — Fri, 22 Sep 2006 15:19:45 +0000

It sounds like you made something interesting, but I wouldn’t want you to spend much time refining it because I probably wouldn’t have immediate use for it. However, other people may find it useful. It’s your call.

By: Polli

Polli — Fri, 22 Sep 2006 01:06:06 +0000

No, I haven’t open sourced. I guess I don’t feel that its “ready” and there are a few quirky part left undone (read memory management).. nor have I looked at the code a few months.

However, if you (or anyone else) like to try it out, I could make the code available somewhere and call it a pre-alpha release.

By: Yariv

Yariv — Thu, 21 Sep 2006 21:00:00 +0000

Hi Polli, your library sounds very cool. Did you open source it by any chance? I’ve never heard of a small Lispy language capable of programming Java GUIs, which in general are far from Lispy. On the mailing list, there’s has been some discussion about using parse-transforms, but I haven’t looked into it myself. It sounds like an approach worth exploring, though.

By: Polli

Polli — Thu, 21 Sep 2006 03:06:43 +0000

I haven't looked at ErlSQL or ErlDB anything but I find this approach interesting. I have myself designed an embedded language (or what you want to call it) when implementing a GUI-lib that uses SWT[1].

This micro language also had very much in common with Lisp. The language has the basic n-ary operators ('+','-', 'and', ..), a few keywords ('set', 'get', ..) and a few other operators ('call', 'new',..).

Using these building blocks you construct large expressions that you encode and send to an external SWT Server (a running java application) that receives, decodes and interprets it.

The result is a quite nifty micro language, that has Erlang its meta language. The result is an odd GUI-library, that makes it quite fun to write GUI applications!*

Have you thought about using parse transforms to create your SQL-expressions? I have not given it much thought but I remember it crossing my mind a few times, while playing around with my library.

*: Unfortunately, I think you need to know about OO and Java to use it efficiently.

[1]: http://www.eclipse.org/swt/

By: Markus

Markus — Wed, 20 Sep 2006 15:36:29 +0000

Many Lisps allow “=” with an arbitrary number of arguments, i.e.
(= a b c d …)
evaluates to #t iff all arguments are equal.

By: Yariv

Yariv — Wed, 20 Sep 2006 08:41:43 +0000

Demius, unfortunately the commas are necessary according to Erlang’s syntax rules. In some cases, Lisp code looks better than Erlang code, and DSELs is apparently one of them :) Sometimes I wish Erlang were a bit more Lispy, but then again I often find Erlang code more readable than Lisp. It’s a give-and-take. But I agree — in this particular example, Lisp wins hands on.