Editing Module:Buffer/doc (section)

====Buffer:_cc====
{{luaself|:_cc|args=clear, copy, meta|args2=0, true}}

Nils all keys of the table referenced by {{code|clear}} and unsets its metatable. If ''clear'' evaluates false, this simply purges the cache at {{luaself|.last_concat}}.

If given a table to {{code|copy}}, this will duplicate all key-value pairs of ''copy'' into ''clear'', cloning any table value recursively via {{code|lang=lua|Buffer:_cc(0, value)}}. This returns the Buffer unless passed the number {{code|lang=lua|0}} as ''clear'', which causes this to create a new table and return that instead. Passing {{code|lang=lua|true}} as ''copy'' is equivalent to passing the Buffer itself. If ''copy'' is not a table, then it will be set as the first item in ''clear'' as long as it is not ''false''.

While this may resemble {{luaref|mw.clone}}, there are several differences, namely that this:
* Gives ''clear'' the same metatable as ''copy'' (or sets <code>meta</code>, if given) as opposed to a "clone" of the metatable.
* Conserves {{luaref|Length operator|Length|y}} attribute (though empty strings may replace some nil keys<ref group="note">For example, given {{code|lang=lua|{nil, 'string'} }} as ''copy'', {{code|lang=lua|Buffer:_cc(clear, copy)}} makes {{code|lang=lua|#clear}} equal <code>2</code>, whereas {{code|lang=lua|#mw.clone{nil, 'string'} }} equals <code>0</code> (as of March 2015). This replicates length by filling clear halfway to the length of copy (the minimum needed to 'trick' Lua) and then setting nil every key that would not trigger recalculation. As a result, keys that would resize ''clear'' when set nil are left as empty strings. Such should be fairly rare; given tables representing every possible way to position a single nil key for all lengths between 2 and 32 (inclusive), only 8.39 percent of such tables would have its nil copied as an empty string instead.Also note that tables returned from {{code|lang=lua|Buffer:_(0, copy)}} have length declared on creation instead, and thus won't have extra strings attached. The odds can be estimated using <math>y {{=}} 0.5 / \sqrt{x}</math>, where <math>y</math> is the upper limit that an arbitrary nil key from ''copy'' of length ranging from 1 to <math>x</math> is imaged as an empty string.</ref>)
* {{luaref|Rawset||y}}s values and iterates without invoking any __pairs {{luaref|Metatables|metamethod|y}}.
* Includes Buffer parent and [[#raw|raw]] attributes (stored externally)

To obtain the key-value pairs left as empty strings in the previous copy op in a table, simply call this again such with value such that <code>rawequal(clear, copy)</code> is true; call :getParent() on this table returns ''clear'' (useful after leeaving the local scope which referenced ''clear'').