ztact.lua

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The ztact.lua module contains a collection of generally convenient and reusable functions.

I started writing ztact.lua before I wrote pozix.c and pzp.lua. As a result, there are currently some functions in ztact.lua that need to be moved to pzp.lua or removed altogether. This will happen at some point when I clean up ztact.lua.

However, there are useful functions inside ztact.lua that will survive the impending cleanup. They are:

• append (t, ...) - append multiple values to a table
• dequeue (queue) - a reasonably efficient queue implementation
• enqueue (queue, ...)
• find (path, ...) - similar to /usr/bin/find, apply mulitple functions to all a path and all its descendants
• get (tree, ...) - tree manipulation
• ivalues (t) - iterate across values alone
• set (tree, ...)
• values (t) - iterate across values alone

-- public domain 20080407 lua@ztact.com


require 'ztact'


-- tree manipulation ---------------------------------------- tree manipulation


-- adding a node...

-- without ztact.set
a = a or {}
a.b = a.b or {}
a.b.c = a.b.c or {}
a.b.c.d = 1

-- with ztact.set:
a = a or {}
ztact.set (a, 'b', 'c', 'd', 1)


-- determining if a node exists...

-- without ztact.get
if a and a.b and a.b.c and a.b.c.d == 1 then
  -- do something
end

-- with ztact.get
if ztact.get (a, 'b', 'c', 'd') == 1 then
  -- do something
end


-- clearing a node (that may not exist!)

-- without ztact.set
-- Note that the below does not collapse the now empty branch
-- a.b.c, it only -- removes the leaf 'd'.
if a and a.b and a.b.c then
  a.b.c.d = nil
end

-- with ztact.set
-- Note that the below will also collapse the empty branch a.b.c, so
-- that a will again be an empty table.
ztact.set (a, 'b', 'c', 'd', nil)

get (rootnode, key1, key2, ..., keyN)

set (rootnode, key1, key2, ..., keyN, value)

Recursively descends into rootnode one key at a time, creating new nodes as needed. Sets rootnode[key1][key2]...[keyN] = value and returns value.

If value is nil then:

Sets rootnode[key1][key2]...[keyN] = nil. If the descent path [key2]...[keyN] does not exists, or if it has no other data leaves (but [key1] does), then the [key2] branch will be collapsed (with rootnode[key1][key2] = nil). Returns the old value of the specified descent path, or nil if the descent path did not exist.