OpenEuphoria

Re: Discussion concerning [POLL] Sequences of types

• Posted by Pete Lomax <petelomax at blueyo?d?r.co.uk> Aug 24, 2007
• 673 views

Derek Parnell wrote:
> 
>   object names -- Can be assigned with anything.
>   sequence names -- Can only be assigned with a sequence.
>   sequence of sequence names -- Can only contain sequences.
>   sequence of sequence of object names -- same as above.
>   sequence of sequence of atom names -- Can only contain sequences, which
>                                       -- can only contain atoms
>   sequence of sequence of integer names -- Can only contain sequences, which
>                                       -- can only contain integers
> 
> If this is too much for some people to grok then maybe a simplified 'type'
> alias
> might be useful.
> 
>    type word_list (sequence of sequence of integer)
>    end type
>    
In the name of code readability, I expected you to favour the latter.
Both could work, I guess, this may be more a matter of personal preference.
Suppose we have a chess program:

sequence of sequence of sequence of integer backtrack_list
sequence of sequence of integer init,best,curr,scratch

vs.

type row(sequence of integer r) end type
type board(sequence of row b) end type
type boards(sequence of board sb) end type
board init,best,curr,scratch
boards backtrack_list

Now you may or may not not need a Phd in the effect of the spice girls on the
global multimedia economy to figure either out, not the point.
A possibly important advantage here is that the innermost bit is now quite
clearly a row not a column. Another example is:

sequence of sequence of sequence of integer filetable

vs.

type char(integer c) end type
type line(sequence of char l) end type
type file(sequence of line f) end type
type texts(sequence of file sf) end type
texts filetable

The clincher for me though is this, for the chess example:

function f(object o)
row r
    if board(o) then
        r=o[1] ...
    elsif row(o) then ...
end function

How would you test for board or row without a named udt?
More subtly, what type do you give r? Yes, you can (easily) figure out from the
sequence of sequence of sequence of integer thing that it needs to be a sequence
of integer, but you are probably just going to give it type object and then the
compiler cannot optimise away any type-checking.

Regards,
Pete