===========================
 Getting started with ISIS
===========================

I recommend reading Section 2.3 of the ISIS manual: http://space.mit.edu/asc/isis/manual.html

TL;DR:
+ To open an interactive ISIS session, enter 'isis' at the command line
+ Every command needs to end with a semi-colon;
+ You can modify settings for interactive mode in your .isisrc file
+ You can execute linux commands by putting an ! before them, e.g. !ls

Here's an example of an isisrc file: http://space.mit.edu/cxc/isis2015/my_isisrc.txt

SYNTAX:
+ ISIS is written in S-lang: http://www.jedsoft.org/slang/docs.html
    when lost, I recommend looking at the language overview section: http://www.jedsoft.org/slang/doc/html/slang-3.html

+ S-lang acts a lot like IDL in that creating an array of numbers and doing math is simple

isis> x = [1,2,3];
isis> x;
isis> print(x);
isis> x = [1:10];
isis> print(x);
isis> y = x^2;
isis> plot(x, y);

============================================
 How to get help with ISIS from within ISIS
============================================

Not sure what command to use? Try 'apropos' to search the ISIS library of functions, e.g.:

How do I plot something?
isis> apropos plot

Call 'help' on any function you find in the list to see how it should be used.

isis> help hplot;

Read it, then scan the "SEE ALSO" portion of the bottom entry to find commands that are related, e.g.

SEE ALSO
    plot, plot_data_counts, window

======================
 Scripting with ISIS
======================

Read Section 3.2 and 3.3 of the ISIS manual: http://space.mit.edu/asc/isis/manual.html

TL;DR:
+ There are several ways to run a script after starting an interactive ISIS session

isis> .load myscript.sl

isis> () = evalfile("myscript.sl");

isis> require("myscript");

NOTE!! The last two options can be used within a script to run another script, 
    but the first option will ONLY work within an interactive session.


+ There are a few ways to run script from the command line:

unix> isis myscript.sl

OR to run it without invoking isis, the first line should read:

#! /usr/bin/env isis

then you should change the permissions so it is executable

chmod +x myscript.sl

and run it from the command line

unix> myscript.sl


SYNTAX:
+ Variables must be declared in a script (unlike the interactive sessions)

variable a, b=Double_Type, c = Integer_Type[10];

+ Comment syntax: Use the % symbol
+ Comment blocks:
#iffalse
This is a 
giant 
  block
  of
  comment text
#endif

+ Function syntax:

define my_cool_funcion( x, y, z )
{
    variable result = x + y^2 + z^3;
    return result;
}

+ Qualifiers can be added to a function, to specify particular options.
    See http://www.jedsoft.org/slang/doc/html/slang-3.html#ss3.2