Atlas Software: Getting Started

If you have not downloaded and installed the software go do download or installing.

Here is what to do next. Let's say you compiled the software in a directory atlasofliegroup, or perhaps you put a precompiled binary there. cd to that directory.

You should be in a directory which contains the excecutable files Fokko and atlas, and subdirectories messages (help files for Fokko) and atlas-scripts (auxiliary and help files for atlas).

On a unix system the command file should give you some information about files (what you see should be similar but not identical): 

atlasofliegroups$ file atlas
atlas: ELF 64-bit LSB  executable, x86-64, version 1 (GNU/Linux), dynamically linked
(uses shared libs), for GNU/Linux 2.6.24, BuildID[sha1]=2e608f86626dad9fbf6354a6142b2b09ab2ee45c, not stripped
atlasofliegroups$
Similarly for Fokko. You might also want to check the permissions on these files 
atlasofliegroups$ ls -l atlas
-rwxr-xr-x 1 jda jda 5969397 Jan 19 02:21 atlas
The crucial point is the first x, which says the file is executable by the user. If this is not the case, do this: 
atlasofliegroups$ chmod u+x atlas
The command atlas, or perhaps ./atlas depending on your settings, should launch the software. The argument
--path=atlas-scripts tells the software where to find the auxiliary files it needs. You should see something like this: 
atlasofliegroups$ ./atlas --path=atlas-scripts
This is 'atlas' (version 0.6, axis language version 0.9),
the Atlas of Lie Groups and Representations interpreter,
compiled on Jan 19 2016 at 02:21:55.   http://www.liegroups.org/
atlas>
First let's make sure the atlas scripts are available. Do this: 
atlas> <basic
The < means read a file, in this case basic.at (the extension is not necessary). You should see many lines of output, from 
atlas> <basic
Starting to read from file 'atlas-scripts//basic.at'.
  Added definition [12] of #: (int->[int])
  Added definition [13] of #: (bool->int)
  ...
to 
Added definition [4] of find: ([[int]],[int]->int)
Defined find_vec: ([vec],vec->int)
atlas>
If not, you should quit and start atlas again, telling it where to find these files. Make sure you gave the correct command atlas --path=atlas-scripts. Check that this subdirectory exists and has many files in it, such as basic.at. You can also give a different --path argument if this directory is located elsewhere.

Once this is working, you can and should load other files. Load all.at to get a recommended set of files: 

atlas> <all
[...output]
atlas>

Next, let's check that readline (command completion, recalling previous commands, etc.) is working. Hit TAB twice. You should see something like: 

atlas> 
Display all 902 possibilities? (y or n)
indicating that command completion is working.

Now do a few simple commands: 

atlas> 1+1
Value: 2
and then 
atlas> set G=SL(2,R)
Identifier G: RealForm
atlas> print_block(trivial (G))
Parameter defines element 2 of the following block:
0:  0  [i1]  1   (2,*)  *(x=0,lam=rho+  [0], nu=  [0]/1)  e
1:  0  [i1]  0   (2,*)  *(x=1,lam=rho+  [0], nu=  [0]/1)  e
2:  1  [r1]  2   (0,1)  *(x=2,lam=rho+  [0], nu=  [1]/1)  1^e
If that works, you're good to go. See the files atlas.help and scripts.help in the atlas-scripts directory.

If you want to use the original software, give the command Fokko. Almost certainly you should use atlas instead.