Atlas of Lie Groups and Representations

For more information see C Compilers for the Mac.

Compiling atlas for the Mac using MacPorts

This is the preferred method. For other Mac options see other methods of installing on the Mac.

You are going to install the gcc C compiler (provided by MacPorts), which is preferred for installing Fokko and atlas. To do so you must first install the XCode C Compiler. See C Compilers for the Mac for an explantion.

(1) Install MacPorts. (If MacPorts is installed on your system go to step (2). Visit, go to Installing MacPorts, and download the dmg file for your version of MAC OSX (for example 10.7.*=Lion). Double click on the dmg file to install MacPorts. You need to be an administrative user, and will need to enter your password.

(2) Install the XCode C compiler. If you already have XCode installed, go to step (3) (XCode is not installed by default).

The XCode package is huge, and includes a lot of unnecessary tools. We recommend downloading and installing just the XCode command line tools, which have everything you need. Alternatively install the entire Xcode package. In either case you will need a (free) Apple ID.

Once you have the XCode command line tools, you will have a C compiler /usr/bin/gcc. You can test this in a terminal window by typing

gcc -v

The response should be something like

Configured with: --prefix=/Applications/

(3) Install the MacPorts (gcc) C Compiler

Open a terminal window (Terminal is available in Applications). All further commands are given from within this window. Give the command:

sudo port install gcc49

to install the the Macports version of gcc. Be sure to be connected to the internet at this point! (Other Macports versions of gcc starting with 4.4 should also work; if you have or download a different version, you'll need to change "4.9" appropriately below.) If you are using only the command line tools of Xcode (not the full XCode installation) ignore the warning about not finding XCode. After a few minutes [or a few hours: some MacPorts things can take a VERY long time. Safest to do this overnight, connected to a power source] you should have /opt/local/bin/gcc-mp-4.9 (the MacPorts C compiler) and /opt/local/bin/g++-mp-4.9 (the MacPorts C++ compiler). You can check these things in a terminal window by typing

ls /opt/local/bin/g*

Also the directory /opt/local/bin has been added to your PATH environment variable.

(4) Install readline


sudo port install readline

to install the readline package.

(5) Set an environment variable, and change your compiler (or go to 5'):

Set the environment variable rl_libs to be "-lreadline -lcurses -L/opt/local/lib".

How to do this depends a bit on your shell. echo $SHELL will tell you your shell. If your shell is bash (and many others) add this line to your .profile file in your home directory (create such a file if it doesn't exist)

export rl_libs="-lreadline -lcurses -L/opt/local/lib"

For the c-shell and variants, add this line to your .cshrc file in your home directory:

setenv rl_libs "-lreadline -lcurses -L/opt/local/lib"

The default mac compiler, /usr/bin/g++ doesn't work. To change the compiler on OS 10.10 and earlier, do this:

sudo mv /usr/bin/g++ /usr/bin/g++-mac
sudo ln -s /opt/local/bin/g++-mp-4.9 /usr/bin/g++
sudo chmod -h 755 /usr/bin/g++

In OS 10.11 (El Capitan) and later, you cannot modify /usr/bin files. You must therefore make sure that /opt/local/bin precedes /usr/bin in your PATH. If you're lucky, Macports took care of this for you. To check, open a new terminal window (the new window ensures that Macports' changes take effect) and type

printenv PATH

The result will be a long list of directories separated by colons: something like


This example shows the good case that /opt/local/bin comes first. If they are in the other (bad) order, you'll need to modify the .profile or .cshrc file in your home directory to fix the problem; consult your local geek or email us for help.

Finally, you need to make the Macports compiler available with the name g++:

sudo ln -s /opt/local/bin/g++-mp-4.9 /opt/local/bin/g++

(5') Alternative: edit the Makefile

Instead of editing the environment variable, in the atlasofliegroups directory, edit the Makefile to read:

# the compiler to use, including language switch
# some C++11 support needed (rvalue references, shared_ptr) but g++-4.4 suffices
CXX = g++-mp-4.9 -std=c++0x

and also edit the line

rl_libs ?= -lreadline

to read

rl_libs ?= -lreadline -lcurses -L/opt/local/lib

(to tell the compiler where to find the readline libraries).

(6) Compile Fokko and atlas

The command


(issued while you are in the atlasofliegroups directory where the Makefile is) should compile both Fokko and atlas.

If you get an error related to readline see installing the readline package.

If you get an error:

ctanglex: Command not found

see installing cwebx

Compilation options: We recommend compiling with

make verbose=true optimize=true

Other possibilities are


(7) Installing Fokko and atlas

To install the executables in [installation directory] and put symlinks in [binary directory], type:

make install INSTALLDIR=[installation directory] BINDIR=[binary directory]

The default BINDIR is INSTALLDIR/../bin.

Example: To install the executables in /usr/local/atlas, and symlinks in /usr/local/bin, type:

sudo make install INSTALLDIR=/usr/local/atlas

(This example only works up to OS 10.10, and you need root access).

Example: To install the executables in /home/[userid]/software/atlas, and symlinks in /home/userid/bin, type:

make install INSTALLDIR=/home/[userid]/software BINDIR=/home/[userid]/bin

Example: Say you unpacked the software in /home/[userid]/atlas_0.6. To leave the software there, and create symlinks in /home/[userid]/bin, type:

make install

Note that the messages (help) directory must be in the same directory as the Fokko executable. Alternatively you can run Fokko with the command


to specify where to find this directory.

Installing cwebx

The software cwebx is needed to compile atlas. If you downloaded a tgz file from the downloads page, you should not need to install cwebx. If you downloaded the software from github using git, then cwebx is included in the directory cwebx, or available from

Running make in the directory cwebx should compile cwebx, and produce the executables cweb/ctanglex and cweb/cweavex. The file sources/interpreter/Makefile tells the compiler to look for these executables. If you move the cwebx directory, or want to use different versions, you must edit this Makefile.

You need to have a working copy of tex in your PATH to run cweavex.