LFE shell built-in variables +/++/+++ -- the tree previous expressions */**/*** -- the values of the previous expressions - -- the current expression output $ENV -- the current LFE environment
Most of these variables are taken directly from Common Lisp and have the same exact meaning. From the Common Lisp HyperSpec for
The variables +, ++, and +++ are maintained by the Lisp read-eval-print loop to save forms that were recently evaluated.
The value of + is the last form that was evaluated, the value of ++ is the previous value of +, and the value of +++ is the previous value of ++.
The variables *, **, and *** are maintained by the Lisp read-eval-print loop to save the values of results that are printed each time through the loop.
The value of * is the most recent primary value that was printed, the value of ** is the previous value of *, and the value of *** is the previous value of **.
The value of - is the form that is currently being evaluated by the Lisp read-eval-print loop.
$ENV variable in the LFE REPL is a critical tool for debugging particularly tricky issues in the REPL (especially useful when creating complex macros).