Editing Module:Buffer/doc (section)

====Buffer:_var====
{{luaself|:_var|args=var, change|args2={ ... }|args3=()}}

Raw appends a Buffer-variable object, which may appear as a different value each time the object (or its container) is converted to a string.<ref group="example">The following contrived example demonstrates most features of {{luaself|:_var|plain=y}}:
:{|
|{{#tag:syntaxhighlight|local H, sep = require'Module:Buffer':_inHTML('div',{'Heading ',_var={nil,'odd','even'},color='blue',['text-decoration']='underline'})
	:_out():_html(true):_html(true):_html(true)
sep = H:_in'This is ':_var():_' - ':_var'A':_var(3,-1):_'\n'
return H:_in(H(sep)):_(sep)
	:_'math:':_var():_'+ 5 =':_var(true,5):_';':_var():_out(0,' '):_var(false):_' - 1 = ':_var()
--[[ produces:
<div style="color:blue;text-decoration:underline">Heading odd</div>This is odd - A3
<div style="color:blue;text-decoration:underline">Heading even</div>This is even - B2
<div style="color:blue;text-decoration:underline">Heading odd</div>This is odd - C1
<div style="color:blue;text-decoration:underline">Heading even</div> This is even - D0
 math: 0 + 5 = 5 ; 5 - 1 = 4   --]]|lang=lua}}
 |}</ref>

Initialize a Buffer-variable object by passing as <code>var</code> a:
* number - which, when strung the first time, appears as that number and reappears as <code>var + change</code> the next time it is strung.
* string - that transforms into the next [[ASCII]] character via {{luaref|string.char||args=var:byte() + change}}.
* table - to return the first (non-nil) item, then the second, and so on as determined by {{luaref|next|args=table}}, looping back to the first item after reaching the last. (Note the ''change'' argument does not apply to table-based Buffer-variables.)
* custom function - to be set as the _build and __tostring method of a variable-object, though instructions for coding such functions are beyond the scope of this manual.

Re-append the same variable object by passing {{code|lang=lua|true}} as the only argument. For non-table-based variables, you may specify ''change'' to append a sister object which transforms the value at the rate specified. Changes are cumulative. Thus, if the original is re-strung after a sister, its value will differ from that of its last appearance by the sum of the original and sister rates and vice versa.

Apply a ''change'' without appending a new variable object to the Buffer by passing {{code|lang=lua|false}}. The shift is effective immediately and may affect previously appended variable objects not yet [[#Buffer:_out|finalized]]. Pass only false (i.e., omit ''change'') to produce the same effect as stringing the original once. Note that the false-change is the only ''change'' table-based Buffer variables will honor.<ref group="note">False cycles tables based on {{luaref|Length operator|#|y}} instead of {{luaref|next}}, which may diverge or error if the table contains nil items.</ref>

Pass nothing to append a version which simply repeats the result of the last stringing. While generally identical in effect to the object generated by <code>:_var(true, 0)</code>, the Buffer-variable will return nothing if strung before any of its sisters.

If passed an explicit nil as the first argument, this is no-op. If passed a boolean before any Buffer-variable has been initialized, this is also a no-op. Note that any op disables future caching at {{luaself|.last_concat|plain=y}} for all Buffer objects in your module (and in any module which may require it).

{{anchor|library}}