PSL Structure Editor
-------------------
Based on the BBN-Lisp editor, circa 1968, and its descendants.
This editor can be entered from inside the break loop or by calling
the functin Edit on a structure to be edited. For information on
other editors do (Help Editor).
Looking Commands:
P Print the current level. The printout replace all sublevels deeper
than 'plevel' by ***. 'plevel' is initialized to 3.
PL n Change 'plevel' to n.
'Stroll around in the structure' commands
n (>0) sets the new current level to the n-th element in the
present current level (Walk down to the n-th sub-expression).
-n (n>0) sets the current level to the n-th cdr in the present current
level.
UP go up to the level you were in just before
T go to the top of the original expression
F s Find the first occurence of s . Test is performed by equal.
After executing, current level is set to the first level s was
a member in.
Structure changing commands:
(Notice, that all these commands are parenthesis expressions.)
(n) Delete the n-th element (in the current level)
(n S ...S ) Replace the n-th element by S ...S .
1 n
(-n S ...S ) Insert before the n-th element the elements S ...S .
1 n
(R S S ) Replace all occurence (in the tree you are placed at)
1 n of S by S (Equal test).
Others:
B Enter a break loop.
OK Leave the editor.
HELP Print this text.
E Eval and print the next expression.