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Announcing Minderbinder v0.2.0

Oct 16, 2012

Minderbinder is a Clojure library for defining unit conversions available at read, compile and run time.

This post is a quick overview. More information is available on the Minderbinder source repo.


Include the following in your Leiningen project.clj file:

[fogus/minderbinder "0.2.0"]

Or include the following in your pom.xml file in the dependencies section:



Minderbinder includes unit conversions for the following units of measure:

  • Time: via #unit/time, base is :milliseconds, ns is minderbinder.time
  • Length: via #unit/length, base is :meters, ns is minderbinder.length
  • Information: via #unit/info, base is :byte, ns is minderbinder.information

Using Minderbinder’s unit reader form

(ns minderbinder.test.core
  (:require minderbinder.time))

(== #unit/time [1 :second]
    #unit/time [1000 :ms])

;;=> true

(== #unit/time [1 :minute 30 :seconds]
    #unit/time [90 :seconds])

;;=> true

Using Minderbinder’s unit parse functions

(ns minderbinder.test.core
  (:require [minderbinder.length :as mbr]))

(mbr/parse-length-unit [1 :km])

;;=> 1000

(mbr/parse-length-unit [1 :ramsden-link])

;;=> 381/1250

Defining custom conversion rules

Defining a unit conversion is accomplished via Minderbinder’s defunits-of macro. The body of the macro expects the following structure:

(defunits-of unit-name base-unit-tag docstring conversion-spec)

The conversion spec part of the body currently allows pairs of mappings defined in reletive terms. The pairs always start with a keyword used as the unit tag. However, the right-hand side of the pair can be one of the following:

  1. Number – defines the value of the unit relative to the base unit
  2. Vector – defines the value of the unit relative to another contained unit
  3. Keyword – defines a single alias for a unit
  4. Set – defined one or more aliases for a unit

A simplified version of Minderbinder’s length conversion definition serves as an example:

(defunits-of length :meter
  "The meter is the length of the path 
  traveled by light in vacuum during a 
  time interval of 1/299,792,458 of 
  a second."

  :m  :meter                   ;; an alias for the base unit
  :km 1000                     ;; a larger value relative to the base unit
  :km #{kilometer kilometers}  ;; multiple aliases for a unit
  :cm 1/100                    ;; a smaller value relative to the base
  :mm [1/10 :cm])              ;; a value relative to another unit

Generated vars

The defunits-of macro will define three things in the namespace where the defunits-of macro appears:

  1. parse-XXX-unit – a function that parses the unit vector according to the conversion spec, returning the total value relative to the base.

  2. unit-of-XXX – a macro that allows the for (unit-of-XXX 1 :foo) that returns the total value relative to the base.

  3. XXX-table – a map describing the unit conversion rules.


  • ClojureScript integration
  • More conversions included by default
  • Base unit changing
  • Cross-unit conversions via function results
  • More plans not yet thought up.


3 Comments, Comment or Ping

  1. Colin Jones

    Awesome name :)

  2. Jon Millett

    How does this compare to frinj?

  3. Nice use of the reader.

    I was sad though to see you hadn’t implemented temperature. Temperature unit conversions is an elegant demonstration of some of the benefits of Lisp syntax and zippers.

    The code’s old and ugly but here’s the basic idea:

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