Re: Array access indirection

[Tim Channon <tc@...>]

Thanks folks including those where I did not reply, all helps.

I do have PIL 2.

Peter Cawley wrote:
>> rt={}
>>
>> rt[var]={[pa1]=va1}
>>
>> rt[var]={[pa2]=va2} -- does not add pair
>>
> You want that last statement to add the key/value pair [pa2]=va2 to
> the table rt[var] ? If so:
> 
> rt[var][pa2] = va2
> 
> The meaning of your instructions:
> 
> rt={} -- Set rt to be an empty table
> rt[var]= {[pa1]=va1} -- Set rt[var] to be a table containing the
> key/pair [pa1] = va1
> rt[var]= {[pa2]=va2} -- Set rt[var] to be a table containing the
> key/pair [pa2] = va2
> 
> The last instruction doesn't add a pair to an existing table, because
> it is overwriting the existing table

The magic is as follows and is one combination I did not try because
neither on their own work. Syntax is inconsistent, to do with runtime
type definition.

require"tprint"

var="fred"

pa1="john"
va1="sam"
pa2="ken"
va2="sal"

rt={} -- new empty table

rt[var]={[pa1]=va1}  -- hint to Lua is subtable and give a it a pair
rt[var][pa2]=va2   -- Lua now knows it is a table,
		 --syntax for adding is different!

var="eek"  -- change table

rt[var]={[pa1]=va1}
rt[var][pa2]=va2

tprint(rt)

[[
"fred":
  "john"="sam"
  "ken"="sal"
"eek":
  "john"="sam"
  "ken"="sal"
]]