# Getting Started with xqerl ## Step 1. Get Erlang/OTP Erlang runs in a virtual machine, much like Java (only different). You will need the VM installed. Instructions can be found [here](https://github.com/erlang/otp/blob/maint/HOWTO/INSTALL.md). #### Windows The installation couldn't be easier! Download the installer, install, run. Running `werl.exe` should give you a shell that looks something like: ``` Erlang/OTP 20 [erts-9.2] [64-bit] [smp:8:8] [ds:8:8:10] [async-threads:10] Eshell V9.2 (abort with ^G) 1> ``` You're all set! ##### Windows 10 Cool thing about Windows 10 is that you can also run Linux natively using **Windows Subsystem for Linux**. This means, you can install the Linux version of Erlang. [Instructions](https://docs.microsoft.com/en-us/windows/wsl/about) can be found on the MS site. #### Other Operating Systems Just follow the build instructions above. ## Step 2. Get rebar3 Rebar3 is a build tool for Erlang. It will make getting xqerl running a breeze. ``` $ git clone https://github.com/erlang/rebar3.git $ cd rebar3 $ ./bootstrap ``` Documentation can be found [here](https://www.rebar3.org/docs#section-installing-from-source). Ensure that rebar3 is in your path to make stuff easier, or use the absolute path in the next step. ## Step 3. Get xqerl and compile it ``` $ git clone https://github.com/zadean/xqerl.git $ cd xqerl $ rebar3 compile ``` You'll may see a few warnings about unused variables or the like. ## Step 4. Start it From the console that just compiled everything run: `rebar3 shell` Initialize everything From the erlang shell, run the following: ```erlang (xqerl_node@some_machine)3> application:ensure_all_started(xqerl). ``` This will initialize the database, web server and also start the code server as well as a few other things. ## Step 5. Start using it ##### Double-quotes must be escaped in the shell: ```erlang (xqerl_node@some_machine)5> xqerl:run("xs:token(\"cats\"), xs:string(\"dogs\"), true() "). [{xqAtomicValue,'xs:token',<<"cats">>},<<"dogs">>,true] ``` Notice here that the xs:string and xs:boolean are Erlang types, and xs:token is marked as a token. ##### Using single-quotes looks cleaner: ```erlang (xqerl_node@some_machine)5> xqerl:run("xs:token('cats'), xs:string('dogs'), true() "). [{xqAtomicValue,'xs:token',<<"cats">>},<<"dogs">>,true] ``` ##### Compile a main-query from file: ```erlang (xqerl_node@some_machine)6> xqerl:compile("docs/src/sudoku2.xq"). file____doc_src_sudoku2_xq ``` This returns the name of the compiled module. Don't write it down! ;-) Save it for later: ```erlang (xqerl_node@some_machine)7> S = xqerl:compile("docs/src/sudoku2.xq"). ``` Now run the XQuery with an empty context map: ```erlang (xqerl_node@some_machine)8> S:main(#{}). ... tn => 'xs:untyped'}], id => {#Ref<0.2416797336.1719664641.241369>,1}, nk => element, nn => {<<>>,<<>>,<<"html">>}, ns => #{<<>> => <<>>}, tn => 'xs:untyped'} ``` Well, that's not very useful! ```erlang (xqerl_node@some_machine)9> Xml = S:main(#{}). (xqerl_node@some_machine)10> xqerl_node:to_xml(Xml). <<"Sudoku - XSLT