Re: Next Lua (5.2) feature request : slicing

[Shannon Stewman <stew@...>]

On Nov 21, 2006, at 4:53 PM, Mike Pall wrote:

> http://lua-users.org/lists/lua-l/2004-11/msg00083.html

I would very much like to see those opcode statistics for  
specifically numeric code.  My one source of constant frustration  
with Lua is how its syntax doesn't really work with common matrix/ 
vector notation.  Writing code in Python feels much more natural;  
this is primarily due to slicing and multiple indexing (that is, mat 
[i,j]).

I know that I can write various "fancy" things that make mat[i][j] 
=2378 work, but I don't like creating intermediate objects where we  
don't need them.

What I would like:

A straightforward extension to indexing that allowed a library to  
implement mat[i,j] by allowing multiple arguments to __index and  
__newindex.  This would eliminate proxy objects (of the sort mat[i] 
[j] requires) and not require painful manual addressing (the highly  
annoying mat[j*NCOL+i]).

Slicing can easily be done with the existing syntax:

mat1[ slice(1,3) ] = mat2[ slice(4,6) ]

which extends nicely to 2+ dimensional arrays:

mat1[ slice(1,3) , slice(1,3) ] = mat2[ slice(4,6), slice(5,7) ]

Cheers!

--
Shannon Stewman         | Let us walk through the waning night,
Caught in a whirlpool,  | As dawn-rays tickle our toes, the dew soothes
A quartering act:       | Our blistered soles, and damp bones stir
Solitude or society?    | As crimson cracks under the blue-grey sky.