ruby: Fix exception on literal empty list

[jackhill/mal.git] / README.md

# mal - Make a Lisp

[![Build Status](https://travis-ci.org/kanaka/mal.svg?branch=master)](https://travis-ci.org/kanaka/mal)

## Description

Mal is a Clojure inspired Lisp interpreter.

Mal is implemented in 51 languages:

* Ada
* GNU awk
* Bash shell
* C
* C++
* C#
* Clojure
* CoffeeScript
* Crystal
* D
* Elixir
* Emacs Lisp
* Erlang
* ES6 (ECMAScript 6 / ECMAScript 2015)
* F#
* Factor
* Forth
* Go
* Groovy
* GNU Guile
* Haskell
* Haxe
* Io
* Java
* JavaScript ([Online Demo](http://kanaka.github.io/mal))
* Julia
* Kotlin
* Lua
* GNU Make
* mal itself
* MATLAB
* [miniMAL](https://github.com/kanaka/miniMAL)
* Nim
* Object Pascal
* Objective C
* OCaml
* Perl
* PHP
* Postscript
* Python
* RPython
* R
* Racket
* Ruby
* Rust
* Scala
* Swift
* Swift 3
* Tcl
* Vimscript
* Visual Basic.NET


Mal is a learning tool. See the [make-a-lisp process
guide](process/guide.md). Each implementation of mal is separated into
11 incremental, self-contained (and testable) steps that demonstrate
core concepts of Lisp. The last step is capable of self-hosting
(running the mal implementation of mal).

The mal (make a lisp) steps are:

* [step0_repl](process/guide.md#step0)
* [step1_read_print](process/guide.md#step1)
* [step2_eval](process/guide.md#step2)
* [step3_env](process/guide.md#step3)
* [step4_if_fn_do](process/guide.md#step4)
* [step5_tco](process/guide.md#step5)
* [step6_file](process/guide.md#step6)
* [step7_quote](process/guide.md#step7)
* [step8_macros](process/guide.md#step8)
* [step9_try](process/guide.md#step9)
* [stepA_mal](process/guide.md#stepA)


Mal was presented publicly for the first time in a lightning talk at
Clojure West 2014 (unfortunately there is no video). See
mal/clojurewest2014.mal for the presentation that was given at the
conference (yes the presentation is a mal program).

If you are interesting in creating a mal implementation (or just
interested in using mal for something), please drop by the #mal
channel on freenode. In addition to the [make-a-lisp process
guide](process/guide.md) there is also a [mal/make-a-lisp
FAQ](docs/FAQ.md) where I attempt to answer some common questions.

## Building/running implementations

The simplest way to run any given implementation is to use docker.
Every implementation has a docker image pre-built with language
dependencies installed. You can launch the REPL using a convenience
target in the top level Makefile (where IMPL is the implementation
directory name and stepX is the step to run):

```
make DOCKERIZE=1 "repl^IMPL^stepX"
    # OR stepA is the default step:
make DOCKERIZE=1 "repl^IMPL"
```


### Ada

The Ada implementation was developed with GNAT 4.9 on debian.
But it also compiles unchanged on windows
if you have windows versions of git, GNAT and (optionally) make.
There are no external dependencies (readline not implemented).

```
cd ada
make
./stepX_YYY
```

### GNU awk

*The GNU awk implementation was created by [Miutsuru kariya](https://github.com/kariya-mitsuru)*

The GNU awk implementation of mal has been tested with GNU awk 4.1.1.

```
cd gawk
gawk -O -f stepX_YYY.awk
```

### Bash 4

```
cd bash
bash stepX_YYY.sh
```

### C

The C implementation of mal requires the following libraries (lib and
header packages): glib, libffi6 and either the libedit or GNU readline library.

```
cd c
make
./stepX_YYY
```

### C++

*The C++ implementation was created by [Stephen Thirlwall (sdt)](https://github.com/sdt)*

The C++ implementation of mal requires g++-4.9 or clang++-3.5 and
a readline compatible library to build. See the `cpp/README.md` for
more details:

```
cd cpp
make
    # OR
make CXX=clang++-3.5
./stepX_YYY
```


### C# ###

The C# implementation of mal has been tested on Linux using the Mono
C# compiler (mcs) and the Mono runtime (version 2.10.8.1). Both are
required to build and run the C# implementation.

```
cd cs
make
mono ./stepX_YYY.exe
```


### Clojure

For the most part the Clojure implementation requires Clojure 1.5,
however, to pass all tests, Clojure 1.8.0-RC4 is required.

```
cd clojure
lein with-profile +stepX trampoline run
```

### CoffeeScript

```
sudo npm install -g coffee-script
cd coffee
coffee ./stepX_YYY
```

### Crystal

*The Crystal implementation of mal was created by [Linda_pp](https://github.com/rhysd)*

The Crystal implementation of mal has been tested with Crystal 0.10.0.

```
cd crystal
crystal run ./stepX_YYY.cr
    # OR
make   # needed to run tests
./stepX_YYY
```

### D

*The D implementation was created by [Dov Murik](https://github.com/dubek)*

The D implementation of mal was tested with GDC 4.8.  It requires the GNU
readline library.

```
cd d
make
./stepX_YYY
```

### Emacs Lisp

*The Emacs Lisp implementation was created by [Vasilij Schneidermann](https://github.com/wasamasa)*

The Emacs Lisp implementation of mal has been tested with Emacs 24.3
and 24.5.  While there is very basic readline editing (`<backspace>`
and `C-d` work, `C-c` cancels the process), it is recommended to use
`rlwrap`.

```
cd elisp
emacs -Q --batch --load stepX_YYY.el
# with full readline support
rlwrap emacs -Q --batch --load stepX_YYY.el
```

### Elixir

*The Elixir implementation was created by [Martin Ek (ekmartin)](https://github.com/ekmartin)*

The Elixir implementation of mal has been tested with Elixir 1.0.5.

```
cd elixir
mix stepX_YYY
# Or with readline/line editing functionality:
iex -S mix stepX_YYY
```

### Erlang

*The Erlang implementation was created by [Nathan Fiedler (nlfiedler)](https://github.com/nlfiedler)*

The Erlang implementation of mal requires [Erlang/OTP R17](http://www.erlang.org/download.html)
and [rebar](https://github.com/rebar/rebar) to build.

```
cd erlang
make
    # OR
MAL_STEP=stepX_YYY rebar compile escriptize # build individual step
./stepX_YYY
```

### ES6 (ECMAScript 6 / ECMAScript 2015)

The ES6 implementation uses the [babel](https://babeljs.io) compiler
to generate ES5 compatible JavaScript. The generated code has been
tested with Node 0.12.4.

```
cd es6
make
node build/stepX_YYY.js
```


### F# ###

*The F# implementation was created by [Peter Stephens (pstephens)](https://github.com/pstephens)*

The F# implementation of mal has been tested on Linux using the Mono
F# compiler (fsharpc) and the Mono runtime (version 3.12.1). The mono C#
compiler (mcs) is also necessary to compile the readline dependency. All are
required to build and run the F# implementation.

```
cd fsharp
make
mono ./stepX_YYY.exe
```

### Factor

*The Factor implementation was created by [Jordan Lewis (jordanlewis)](https://github.com/jordanlewis)*

The Factor implementation of mal has been tested with Factor 0.97
([factorcode.org](factorcode.org)).

```
cd factor
FACTOR_ROOTS=. factor -run=stepX_YYY
```

### Forth

*The Forth implementation was created by [Chris Houser (chouser)](https://github.com/chouser)*

```
cd forth
gforth stepX_YYY.fs
```

### Go

The Go implementation of mal requires that go is installed on on the
path. The implementation has been tested with Go 1.3.1.

```
cd go
make
./stepX_YYY
```


### Groovy

The Groovy implementation of mal requires Groovy to run and has been
tested with Groovy 1.8.6.

```
cd groovy
make
groovy ./stepX_YYY.groovy
```

### GNU Guile 2.1+

*The Guile implementation was created by [Mu Lei (NalaGinrut)](https://github.com/NalaGinrut).*

```
cd guile
guile -L ./ stepX_YYY.scm
```

### Haskell

Install the Haskell compiler (ghc/ghci), the Haskell platform and
either the editline package (BSD) or the readline package (GPL). On
Ubuntu these packages are: ghc, haskell-platform,
libghc-readline-dev/libghc-editline-dev

```
cd haskell
make
./stepX_YYY
```

### Haxe

The Haxe implementation of mal requires Haxe version 3.2 to compile.
Four different Haxe targets are supported: Neko, Python, C++, and
JavaScript.

```
cd haxe
# Neko
make all-neko
neko ./stepX_YYY.n
# Python
make all-python
python3 ./stepX_YYY.py
# C++
make all-cpp
./cpp/stepX_YYY
# JavaScript
make all-js
node ./stepX_YYY.js
```

### Io

*The Io implementation was created by [Dov Murik](https://github.com/dubek)*

The Io implementation of mal has been tested with Io version 20110905.

```
cd io
io ./stepX_YYY.io
```

### Java 1.7

The Java implementation of mal requires maven2 to build.

```
cd java
mvn compile
mvn -quiet exec:java -Dexec.mainClass=mal.stepX_YYY
    # OR
mvn -quiet exec:java -Dexec.mainClass=mal.stepX_YYY -Dexec.args="CMDLINE_ARGS"
```

### JavaScript/Node

```
cd js
npm update
node stepX_YYY.js
```

### Julia

The Julia implementation of mal requires Julia 0.4.

```
cd julia
julia stepX_YYY.jl
```

### Kotlin

*The Kotlin implementation was created by [Javier Fernandez-Ivern](https://github.com/ivern)*

The Kotlin implementation of mal has been tested with Kotlin 1.0.

```
cd kotlin
make
java -jar stepX_YYY.jar
```

### Lua

Running the Lua implementation of mal requires lua 5.1 or later,
luarocks and the lua-rex-pcre library installed.

```
cd lua
make  # to build and link linenoise.so
./stepX_YYY.lua
```

### Mal

Running the mal implementation of mal involves running stepA of one of
the other implementations and passing the mal step to run as a command
line argument.

```
cd IMPL
IMPL_STEPA_CMD ../mal/stepX_YYY.mal

```

### GNU Make 3.81

```
cd make
make -f stepX_YYY.mk
```

### Nim 0.11.0

*The Nim implementation was created by [Dennis Felsing (def-)](https://github.com/def-)*

Running the Nim implementation of mal requires Nim 0.11.0 or later.

```
cd nim
make
  # OR
nimble build
./stepX_YYY
```

### Object Pascal

The Object Pascal implementation of mal has been built and tested on
Linux using the Free Pascal compiler version 2.6.2 and 2.6.4.

```
cd objpascal
make
./stepX_YYY
```

### Objective C

The Objective C implementation of mal has been built and tested on
Linux using clang/LLVM 3.6. It has also been built and tested on OS
X using XCode 7.

```
cd objc
make
./stepX_YYY
```

### OCaml 4.01.0

*The OCaml implementation was created by [Chris Houser (chouser)](https://github.com/chouser)*

```
cd ocaml
make
./stepX_YYY
```

### MATLAB

The MATLAB implementation of mal has been tested with MATLAB version
R2014a on Linux. Note that MATLAB is a commercial product. It should
be fairly simple to support GNU Octave once it support classdef object
syntax.

```
cd matlab
./stepX_YYY
matlab -nodisplay -nosplash -nodesktop -nojvm -r "stepX_YYY();quit;"
    # OR with command line arguments
matlab -nodisplay -nosplash -nodesktop -nojvm -r "stepX_YYY('arg1','arg2');quit;"
```

### miniMAL

[miniMAL](https://github.com/kanaka/miniMAL) is small Lisp interpreter
implemented in less than 1024 bytes of JavaScript. To run the miniMAL
implementation of mal you need to download/install the miniMAL
interpreter (which requires Node.js).
```
cd miniMAL
# Download miniMAL and dependencies
npm install
export PATH=`pwd`/node_modules/minimal-lisp/:$PATH
# Now run mal implementation in miniMAL
miniMAL ./stepX_YYY
```

### Perl 5.8

For readline line editing support, install Term::ReadLine::Perl or
Term::ReadLine::Gnu from CPAN.

```
cd perl
perl stepX_YYY.pl
```


### PHP 5.3

The PHP implementation of mal requires the php command line interface
to run.

```
cd php
php stepX_YYY.php
```

### Postscript Level 2/3

The Postscript implementation of mal requires ghostscript to run. It
has been tested with ghostscript 9.10.

```
cd ps
gs -q -dNODISPLAY -I./ stepX_YYY.ps
```

### Python (2.X or 3.X)

```
cd python
python stepX_YYY.py
```

### RPython

You must have [rpython](https://rpython.readthedocs.org/) on your path
(included with [pypy](https://bitbucket.org/pypy/pypy/)).

```
cd rpython
make        # this takes a very long time
./stepX_YYY
```

### R

The R implementation of mal requires R (r-base-core) to run.

```
cd r
make libs  # to download and build rdyncall
Rscript stepX_YYY.r
```

### Racket (5.3)

The Racket implementation of mal requires the Racket
compiler/interpreter to run.

```
cd racket
./stepX_YYY.rkt
```

### Ruby (1.9+)

```
cd ruby
ruby stepX_YYY.rb
```

### Rust (1.0.0 nightly)

The rust implementation of mal requires the rust compiler and build
tool (cargo) to build.

```
cd rust
cargo run --release --bin stepX_YYY
```

### Scala ###

Install scala and sbt (http://www.scala-sbt.org/0.13/tutorial/Installing-sbt-on-Linux.html):

```
cd scala
sbt 'run-main stepX_YYY'
    # OR
sbt compile
scala -classpath target/scala*/classes stepX_YYY
```

### Swift

*The Swift implementation was created by [Keith Rollin](https://github.com/keith-rollin)*

The Swift implementation of mal requires the Swift 2.0 compiler (XCode
7.0) to build. Older versions will not work due to changes in the
language and standard library.

```
cd swift
make
./stepX_YYY
```

### Swift 3

The Swift 3 implementation of mal requires the Swift 3.0 compiler. It
has been tested with the development version of the Swift 3 from
2016-02-08.

```
cd swift3
make
./stepX_YYY
```

### Tcl 8.6

*The Tcl implementation was created by [Dov Murik](https://github.com/dubek)*

The Tcl implementation of mal requires Tcl 8.6 to run.  For readline line
editing support, install tclreadline.

```
cd tcl
tclsh ./stepX_YYY.tcl
```

### Vimscript

*The Vimscript implementation was created by [Dov Murik](https://github.com/dubek)*

The Vimscript implementation of mal requires Vim to run.  It has been tested
with Vim 7.4.

```
cd vimscript
./run_vimscript.sh ./stepX_YYY.vim
```

### Visual Basic.NET ###

The VB.NET implementation of mal has been tested on Linux using the Mono
VB compiler (vbnc) and the Mono runtime (version 2.10.8.1). Both are
required to build and run the VB.NET implementation.

```
cd vb
make
mono ./stepX_YYY.exe
```



## Running tests

### Functional tests

The are over 600 generic functional tests (for all implementations)
in the `tests/` directory. Each step has a corresponding test file
containing tests specific to that step. The `runtest.py` test harness
launches a Mal step implementation and then feeds the tests one at
a time to the implementation and compares the output/return value to
the expected output/return value.

To simplify the process of running tests, a top level Makefile is
provided with convenient test targets.

* To run all the tests across all implementations (be prepared to wait):

```
make test
```

* To run all tests against a single implementation:

```
make "test^IMPL"

# e.g.
make "test^clojure"
make "test^js"
```

* To run tests for a single step against all implementations:

```
make "test^stepX"

# e.g.
make "test^step2"
make "test^step7"
```

* To run tests for a specific step against a single implementation:

```
make "test^IMPL^stepX"

# e.g
make "test^ruby^step3"
make "test^ps^step4"
```

### Self-hosted functional tests

* To run the functional tests in self-hosted mode, you specify `mal`
  as the test implementation and use the `MAL_IMPL` make variable
  to change the underlying host language (default is JavaScript):
```
make MAL_IMPL=IMPL "test^mal^step2"

# e.g.
make "test^mal^step2"   # js is default
make MAL_IMPL=ruby "test^mal^step2"
make MAL_IMPL=python "test^mal^step2"
```

### Starting the REPL

* To start the REPL of an implementation in a specific step:

```
make "repl^IMPL^stepX"

# e.g
make "repl^ruby^step3"
make "repl^ps^step4"
```

* If you omit the step, then `stepA` is used:

```
make "repl^IMPL"

# e.g
make "repl^ruby"
make "repl^ps"
```

* To start the REPL of the self-hosted implementation, specify `mal` as the
  REPL implementation and use the `MAL_IMPL` make variable to change the
  underlying host language (default is JavaScript):
```
make MAL_IMPL=IMPL "repl^mal^stepX"

# e.g.
make "repl^mal^step2"   # js is default
make MAL_IMPL=ruby "repl^mal^step2"
make MAL_IMPL=python "repl^mal"
```

### Performance tests

Warning: These performance tests are neither statistically valid nor
comprehensive; runtime performance is a not a primary goal of mal. If
you draw any serious conclusions from these performance tests, then
please contact me about some amazing oceanfront property in Kansas
that I'm willing to sell you for cheap.

* To run performance tests against a single implementation:
```
make "perf^IMPL"

# e.g.
make "perf^js"
```

* To run performance tests against all implementations:
```
make "perf"
```

### Generating language statistics

* To report line and byte statistics for a single implementation:
```
make "stats^IMPL"

# e.g.
make "stats^js"
```

* To report line and bytes statistics for general Lisp code (env, core
  and stepA):
```
make "stats-lisp^IMPL"

# e.g.
make "stats-lisp^js"
```

## Dockerized testing

Every implementation directory contains a Dockerfile to create
a docker image containing all the dependencies for that
implementation. In addition, the top-level Makefile contains support
for running the tests target (and perf, stats, repl, etc) within
a docker container for that implementation by passing *"DOCKERIZE=1"*
on the make command line. For example:

```
make DOCKERIZE=1 "test^js^step3"
```

Existing implementations already have docker images built and pushed
to the docker registry. However, if
you wish to build or rebuild a docker image locally, the toplevel
Makefile provides a rule for building docker images:

```
make "docker-build^IMPL"
```


**Notes**:
* Docker images are named *"kanaka/mal-test-IMPL"*
* JVM-based language implementations (Groovy, Java, Clojure, Scala):
  you will probably need to run these implementations once manually
  first (make DOCKERIZE=1 "repl^IMPL")before you can run tests because
  runtime dependencies need to be downloaded to avoid the tests timing
  out. These dependencies are download to dot-files in the /mal
  directory so they will persist between runs.


## License

Mal (make-a-lisp) is licensed under the MPL 2.0 (Mozilla Public
License 2.0). See LICENSE.txt for more details.