Editing Module:Buffer/doc (section)

====Buffer:_G====
{{luaself|:_G|args=name, save}}
{{distinguish|text=the [[#G object|&sect; _G object]], which chain call looks the same but may behave differently.}}

Pass <code>name</code> and <code>save</code> to assign the object passed as ''save'' to a global variable via {{luaref|rawset|args=_G, name, save}}.<ref group="note">Actually, the first argument to rawset is a local variable <code>[[#new_G|new_G]]</code> which generally equals _G but not always, to be detailed in a later section.</ref>

Pass only ''name'' and this substitutes ''self'' for ''save'' to assign the Buffer object to <code>_G[name]</code> instead. Give an explicit nil as ''save'' to unset a global. This returns the Buffer object as well as any argument given after ''name''.

This is a no-op when ''name'' is nil or a boolean, or, when ''save'' (eventually) evaluates true and {{luaref|rawequal|args=save, rawget(new_G, name)}} also returns true.
{{anchor|metaglobal}}

If the named global already exists, this "backs up" the old value by moving it to the meta __index of the global table, setting a new metatable if none exists.<ref group="note">If the meta global has an __index which is a function (as is the case after requiring [[Module:No globals]]), the back-up op aborts without throwing an error.</ref> Retrieving the old value requires unsetting the new one via {{luaself|:_R}} (more details in that section). If overwritten a third time, the first value is discarded and the second takes its place in the back up.

If a metaglobal variable exists but the global is nil, this sets the global without unsetting the metaglobal (i.e. does not back up a nil global). An exception is when this is given an explicit nil as ''save'' and only the metaglobal exists; thus, passing nil twice for the same ''name'', unsets the key in both the global table and its metaindex.