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A collection of documentation for Clojure functions, macros, and other vars. This extra documentation can easily be added to the doc strings in a running Clojure process, such that (doc ==) will show the standard doc string, plus the extra documentation. Here is the output of (doc ==) with unmodified Clojure 1.5.1:

user=> (doc ==)
([x] [x y] [x y & more])
  Returns non-nil if nums all have the equivalent
  value (type-independent), otherwise false

Here is the output of (doc ==) after loading thalia extended doc strings (no modification to Clojure source code is required):

user=> (doc ==)
([x] [x y] [x y & more])
  Returns non-nil if nums all have the equivalent
  value (type-independent), otherwise false
--------- ^^^ original docs --------- VVV unofficial extra docs ---------
(== x y) is true if x and y are both numbers, and represent
numerically equal values.  Unlike =, there are no separate
'categories' of numeric values that are treated as always unequal to
each other.  If you call == with more than two arguments, the result
will be true when all consecutive pairs are ==.  An exception is
thrown if any argument is not a numeric value.

Exceptions, or possible surprises:

* == is false for BigDecimal values with different scales, e.g. (==
  1.50M 1.500M) is false.
* 'Not a Number' values Float/NaN and Double/NaN are not equal to any
  value, not even themselves.


    user=> (= 2 2.0)   ; = has different categories integer and floating point
    user=> (== 2 2.0)  ; but == sees same numeric value
    user=> (== 5 5N (float 5.0) (double 5.0) (biginteger 5))
    user=> (== 5 5.0M) ; this is likely a bug
    user=> (== Double/NaN Double/NaN)  ; this is normal
    user=> (== 2 "a")
    ClassCastException java.lang.String cannot be cast to java.lang.Number  clojure.lang.Numbers.equiv (

This documentation is intended to describe the way things behave in particular versions of Clojure, including examples, bugs, and issues Clojure programmers should be cautious about. It has no official status as Clojure documentation. You should not rely on any of it as a promise that future Clojure versions will continue to behave in the ways documented.

Releases and dependency information

Latest stable release: 0.1.0

Leiningen dependency information:

[thalia "0.1.0"]

Maven dependency information:



Add this to the dependencies of your Leiningen project:

[thalia "0.1.0"]

If you wish it to be part of the dependencies in all of your Leiningen projects at the REPL, add this to your $HOME/.lein/profiles.clj file:

{:repl {:dependencies [[thalia "0.1.0"]]}}

In the REPL, you can add the extra docs to the normal doc strings with these commands:

user=> (require 'thalia.doc)
user=> (thalia.doc/add-extra-docs!)  ; (thalia.doc/add-extra-docs! :language "en_US") if you get a locale related error

To test it, look at the output of (doc ==).

It is expected that this collection of documentation will grow slowly over time, as it is written.

Web docs

Here are links to some docs that were written in Markdown format for browsing on Github. I am not sure whether I will be enhancing these in the future. My current thinking is to focus on making enhanced doc strings for use in the REPL rather than web browsing.

Developer documentation

The basic flow is:

  • Create text files (in Github-flavored Markdown format) containing extended doc strings in a directory beneath the doc/project-docs directory. See 'Directory structure' below for the path names that should be used.

  • Create one file resource/<language>.clj per language for all extended doc strings written in that language. See 'Create language resource files' below.

  • Use Leiningen to create a JAR file containing a little bit of Clojure code and the files in the resource directory. This is deployed for others to use, e.g. on See 'Create JAR file' below.

  • Create tests in test/thalia/doc_test.clj, or some other test file. These should test all examples given in the extended doc strings, and perhaps more. See 'Run tests' below.

Directory structure

The path name of each text file should be of the following form, where / characters are used as on Mac OS X and Linux to separate directory names in the path.


Below are some example paths for the language US English, abbreviated en_US. Execute the expression (str (java.util.Locale/getDefault)) at the REPL to see the abbreviation for your language.

The project is clojure.core, version 1.5.1, namespace clojure.string, symbol replace:


Below is an example for everything the same as above, except the namespace is clojure.core and the symbol is ==. The file name has been modified in a way similar to how special characters are modified when they appear in URLs. If you have a project, version, namespace, or symbol name with any characters that are not ASCII alphabetic, numeric, nor the - character, you can use the function thalia.core/encode-url-component to see what the file name should be.


Create language resource files

Run this command:

lein run create-doc-rsrc en_US

Other languages besides US English may be supported in the future, if someone writes doc strings in those languages.

Create JAR file

Run one or more of the following commands.

# To install in your local Maven repo, usually in $HOME/.m2
lein install

# To create a JAR file locally
lein jar

# To deploy to
lein deploy clojars

Run tests

There is definitely repetition involved here in having the same or similar code in both the doc string text files and the unit tests.

In their current form, running the tests is quite simple:

lein test-all

It would be preferable not to do so, e.g. by having an automated way to extract the examples from the doc strings and execute them, verifying the output is as shown in the example. If someone knows of a good way to do that, please let me know. Something like doctest in Python would be good.

Creating directory tree skeleton

These instructions have only been tested with Mac OS X and Linux, although they might work on Windows with Cygwin installed. They are not expected to work with Windows (without Cygwin) because of the bash shell scripts involved.

TBD: Flesh these instructions out. They involve using lein-clojuredocs.

Also these commands:

lein run json2edn
lein run create-empty-doc-files

For Clojure contrib libraries, the bash script scripts/ may be useful.

To do

Write extended doc strings for many more vars.

Create a function or macro (topic ) that can be used to show documentation about topics that are not necessarily about a particular var, similary to Python's 'topics' in its help system. There are already references to (topic Equality) and (topic Comparators) in existing doc strings.

Try to enable (optional) less-like pager behavior for long doc strings. The following StackOverflow page may lead to a solution:

If we ever have a lot of these, consider making a version of the tooltip-enabled Clojure cheat sheet with the longer doc strings, with a line limit much longer than the current 15 lines.


Copyright (c) 2013-2015 Andy Fingerhut

Distributed under the Eclipse Public License.


A collection of documentation for Clojure symbols






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