Comments on: Computing with units and dimensions

By: Eric Fraga

Eric Fraga — Wed, 13 Jul 2011 20:11:47 +0000

Ah, I see! Sorry I misunderstood your point. I agree completely that adding conversions between Celsius and Fahrenheit is not worth the effort. So long as Kelvin is there, I’m happy!

By: khinsen

khinsen — Sat, 09 Jul 2011 15:04:32 +0000

Kelvin is in there, of course, it’s an SI unit after all. Adding Rankin is trivial, as is adding most other units: All it takes is a defunit statement containing the conversion factor to some already known unit combination. What’s not possible without adding lots of code is units whose zero is non-standard, which in practice means Celsius and Fahrenheit.

By: Eric Fraga

Eric Fraga — Fri, 08 Jul 2011 18:19:05 +0000

If I may comment on this: “I don’t think that introducing that amount of complexity is justified, considering that daily-life temperatures are rarely combined in computations with quantities of other dimensions.”:

It is true that working with temperatures can be complex, especially if you allow the use of non-0 based scales like Celsius and Fahrenheit. However, if you stick to Kelvin (and/or Rankin), there is little complexity. More to the point, there are plenty of problems that require combining temperatures with other units, especially in chemical engineering and physics problems dealing with heat transport.

I would really appreciate you reconsidering the above, at least adding support for Kelvin (and/or Rankin)! If I get a chance, and if my Clojure expertise is up to it, I may have a go myself, but I assume it should be trivial for you to do.

Thanks, in any case, for what looks like a great addition to the Clojure-verse!

By: Artie

Artie — Sat, 29 May 2010 22:26:05 +0000

Works now! Cheers!

By: khinsen

khinsen — Wed, 26 May 2010 08:32:15 +0000

Please try release 0.2.2, which works with the current version of Clojure 1.2. Make sure that you have a recent version of clojure-contrib as well; I fixed a relevant bug there yesterday!

By: khinsen

khinsen — Tue, 25 May 2010 09:56:20 +0000

The error message looks strange indeed because there is no line 1917 in file units.clj!

However, I suspect that your problem is due to the Clojure version you use. The units module was written for an early development version of Clojure 1.2. Older Clojure releases (1.0 and 1.1) don’t have the deftype mechanism that is heavily used, and in recent developmenet versions of Clojure 1.2 this mechanism has changed so much that the units modules doesn’t work anymore. As a consequence, there are only a few snapshots of the development version that actually work with clj-units.

I am working on adapting clj-units to the current Clojure 1.2 development versions, but since I don’t have much time right now, this might take another week or two. Please be patient!

By: Artie

Artie — Sat, 22 May 2010 18:31:32 +0000

Two things.

The clojars site lists the pom’s version as 0.2.1 but the actual version that is available is 0.2.0.
Also, trying to use your example, I get this error:

(ns+ unit-demo
(:clone nstools.generic-math)
(:from units dimension? in-units-of)
(:require [units.si :as si]))
java.lang.IllegalArgumentException: Unsupported option(s) – :as (units.clj:1917)

Not sure what’s wrong, I’m able to use (:require [foo :as bar]) elsewhere in my code.