# Getting started

## Installation

The rest of these docs assume that you’re familiar with the basics of Clojure, and have a working copy of Leiningen (version >= 2) installed. If you’re not yet familiar with Leiningen then you should head over to the Leiningen website and get it installed first. It’s a really nice tool that makes things very easy!

Gorilla is packaged as a Leiningen plugin. To use Gorilla in one of your Leiningen projects, then add the following to the :plugins section of that project’s project.clj file:

[lein-gorilla "0.4.0"]


Your completed project.clj file might look something like this:

(defproject gorilla-test "0.1.0-SNAPSHOT"
:description "A test project for Gorilla REPL."
:dependencies [[org.clojure/clojure "1.6.0"]]
:main ^:skip-aot gorilla-test.core
:target-path "target/%s"
:plugins [[lein-gorilla "0.4.0"]]
:profiles {:uberjar {:aot :all}})


That’s it. You should now be able to run lein gorilla from within the project directory and get started.

## Usage

When you run lein gorilla it will start up the REPL server, and print a web-link to the console. Point your web-browser at this link to get going (hint for Mac users: try ctrl-clicking the link). You can open as many browser windows as you like with this link, each will get its own nREPL session to work in, but share the same nREPL instance (in case you’re not familiar with nREPL’s terminology: this means all windows will share definitions etc, but each window will separately keep track of which namespace you’re working in - try it, you’ll see it’s quite natural).

Once you’ve got a web-browser pointed at Gorilla you can use it just like a REPL. Type some clojure code in, and hit shift+enter to evaluate it. The results are displayed below the code, along with any console output or errors that were generated. Gorilla offers nREPL’s autocomplete function, hit ctrl+space to see what nREPL has to suggest (unless you’re using Firefox on Mac - see the commands section below for more info.)

### Plotting graphs

One of the most handy features of Gorilla is the ability to plot graphs. The plotting library gorilla-plot is integrated into Gorilla and is always available without explicitly including it as a dependency in your project.clj. Full documentation for gorilla-plot is available at the plotting page, but to get you started, let’s give a short summary.

There are five functions that should cover many plotting needs. These functions are in the gorilla-plot.core namespace, so you will need to use or require it before starting. The functions are:

• (list-plot data) where data can either be a sequence of y-values, or a sequence of (x y) pairs.
• (plot func [start end]) which will evaluate and plot func over the given range.
• (histogram data) where data is a list of values.
• (bar-chart categories values) where categories are the category names, and values their values.
• (compose plot1 plot2 & more) which tries to compose together the given plots. Note that composing a bar-chart with other plots will give odd results, as it’s not obvious how to compose category-scales.

These functions take many options, look at the detailed docs for more help.

There’s a short video talking a little more about how the plots work, and how they try and fit nicely with the Clojure way of thinking (plots are values) which might interest you.

### Other kinds of output

Plots aren’t the only way that Gorilla can give you a more useful view into your Clojure values. There are a number of other built in functions to view data:

• table-view in the gorilla-repl.table namespace lets you view lists-of-lists as tables. You can supply an optional vector as a :columns argument to label the columns of the table.
• latex-view in the gorilla-repl.latex namespace lets you view a string as its rendered LaTeX form.
• html-view in the gorilla-repl.html namespace lets you view a string rendered as HTML.

These built-in view functions are just the beginning though. Gorilla REPL has a very flexible, extensible renderer so you can plug in new ways of viewing values. If your favourite library doesn’t have the viewers for the data that you want, then file a feature request, or even better write some code and contribute it!

A feature worth mentioning here is value-copy-and-paste. Although Gorilla shows some values (like graphs, tables) with fancy formatting, the underlying Clojure value is always there to be used. If you alt-click on any output in Gorilla it will give you the readable Clojure value to work with (if it exists).

### Editor commands

Before we can go much further we will need to introduce editor commands. You don’t need them right now, but you can see all of the editor commands by hitting ctrl+g twice in succession (alt-g on Windows and Linux, see below), or clicking on the feint menu icon in the top right hand corner of the Gorilla window. Hopefully they are all self-explanatory, or at least you can figure them out easily enough.

You’ll probably want to use keyboard shortcuts to issue the editor commands if you use Gorilla much: they are usually a sequence of two keypresses. On Windows these are of the form alt+a alt+b and on other platforms they are of the form ctrl+a ctrl+b. This document writes them in the format suitable for Mac - if you’re on Windows/Linux replace the ctrls with alts. An attempt has been made to make sure the commands work across popular browsers and operating systems (which is not as easy as you might think). The one exception is the autocomplete command which doesn’t work on Firefox on the Mac, as it steals ctrl+space for its own use, somewhat controversially. You can instead use ctrl+g ctrl+a if you’re using Firefox.

Note that you can auto-indent code in the editor by selecting it and hitting shift-tab. This can be a nice way to spot syntax errors :-)

### Making notes

So far we’ve used Gorilla as a fancy REPL, but we can also think of it as a tool for making documents, which we call ‘worksheets’. As well as including snippets of Clojure code, a Gorilla worksheet can include notes, which are written in Markdown format. To add notes you need to first tell Gorilla that it should interpret a snippet of text as notes, rather than Clojure code. To do this place the cursor in the segment (a segment being one of the boxes containing a snippet of code/notes) that you want to use for notes and hit, ctrl+g ctrl+m (g for Gorilla, m for Markdown). You can then feel free to put any Markdown you like in there. The notes segments also support LaTeX formulae. To write a formula you simply surround the latex code with $$, or @@ if you want the formula to appear inline. So for instance, the contents of a Markdown segment could be: This is an inline formula, @@\sin(x)@@, and this is on its own line:$$\int_0^{2\pi}\sin^2(x) \textrm{d}x


Note: currently you will need to be online in order for LaTeX to render properly.

#### Spell checking

Due to limitations of the underlying CodeMirror component, spell checking of the notes is currently not possible. A workaround is to open the worksheet file (see below) with a Clojure editor which supports spell checking. Emacs work very well for this, with its ‘ispell-comments-and-strings” command which ignores code blocks during the spell check. The document should be saved without the output. Gorilla has a command to clear the output of all the segments, which makes this easy.

### Worksheet files

You can save the contents of a window to a worksheet file. This will include everything you see, the code, the output, graphs, notes and mathematics, the lot. To save a file just hit ctrl+g ctrl+s. If you haven’t already saved the file it will prompt for a filename, which is given relative to the project. To load a file, use ctrl+g ctrl+l (note that Gorilla files must end in .clj or .cljw to be loaded). By convention, I often find it convenient to store my worksheets in a directory called ws at the root of the project (alongside src etc) but you, of course, can store them wherever you want. A neat feature is that these worksheet files are just plain Clojure files with some magic comments. This means it’s really easy to interactively develop your code in Gorilla, and then turn it into a library when it stabilises.

### doc, source and other REPL commands

You might be used to using doc and source at the command-line REPL. By default these are not imported into the user namespace when Gorilla starts, but if you’d like to use them then you just need to run (use 'clojure.repl) to bring them into scope.

### Other editors

Gorilla works well alongside other editors and there’s a page with hints on setting up your favourite environment to work well with Gorilla.

### Server-side usage

Many people find it useful to run Gorilla on a server. As all of Gorilla’s communication happens over HTTP and websockets, this is usually very easy. A couple of notes:

• Any user who has access to Gorilla effectively has access to the server machine with the privileges of the JVM process. So, you will want to ensure that only trusted users have access. Gorilla does not offer any built-in authentication mechanism. It is recommended to either use a reverse-proxy, network-level controls, or access through ssh tunnels (see next point).
• In the case there is a firewall or proxy between your browser and a remote Gorilla server, it might be possible that the websocket connection to the Gorilla repl is blocked. One solution to this is to tunnel access over SSH, which can also be used as a user authentication method.
• By default Gorilla does not bind to external IPs, so is only accessible from the server itself. If you want to expose Gorilla to the network, then see the advanced configuration options below.