[Boost-users] Multi-Array indexing

Subject: [Boost-users] Multi-Array indexing
From: todd keeler (tkeeler_at_[hidden])
Date: 2008-10-20 15:37:33

Hi,  I'd like to understand how the Boost Multi-array implements 
multiple indexing using the regular square bracket operator.

I've waded through the template code for a few hours,  from what I 
understand, there's a nested bunch of sub-arrays which leads to a final 
object which offers a reference into the data array.

I still can't figure out, however, how it solves this problem:

Consider a Multi-Array  A with dimension 3,
Calling 
A[ i ][ j ][ k ] 

requires a call to

A[ i ]  which returns a Subarray, S1

The subarray gets indexed
S1[ j ] 
and another subarray S2 is returned.

however S2[k]  doesn't return a subarray, but a
reference to the data in the multiarray.

However,  S1 and S2 are the same object (subarray),  hence require the 
same overloaded operator, returning the same type.
making this unfeasible.
 
Therefore,  the only way I can think to eliminate this dilemma is to 
have a different object type for every dimension.  I'm not sure if this 
is what Multi-array does, but I'd sure like to know how it's done .

Thanks
Todd