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Date: Sat, 30 Dec 2017 15:52:34 -0800 (PST)
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Xref: reader02.eternal-september.org comp.lang.ada:49707
Date: 2017-12-30T15:52:34-08:00
List-Id: <comp.lang.ada>

On Saturday, December 30, 2017 at 9:41:56 AM UTC-8, Simon Wright wrote:
> Simon Wright <simon@pushface.org> writes:
> 
> > Mace Ayres <mace.ayres@gmail.com> writes:
> >
> >> if ... OR also, the cell/record has a field with its triad, a constant
> >> property.
> >
> > Don't understand this.
> 
> Oh, I see, it's Sudoku, and those are the given cells.
> 
> Anyway, this looks simple enough for checking whether the value is
> already in the block:
=============

Thanks Simon. This is exactly what I needed. My thoughts were moving toward the rythm of threes and increments  in start and length of each block, but it would have taken me a while toga to the parenthesized leitmotif you capture.
Excellent!

Are you a professional Ada programmer?

=====================
> 
>    function Check_Block (For_Value : Integer;
>                          At_Row : Grid_Coordinate;
>                          At_Column : Grid_Coordinate;
>                          In_Grid : Grid) return Boolean
>    is
>       Row_First : constant Grid_Coordinate := ((At_Row    - 1) / 3) * 3 + 1;
>       Col_First : constant Grid_Coordinate := ((At_Column - 1) / 3) * 3 + 1;
>    begin
>       for Row in Row_First .. Row_First + 2 loop
>          for Col in Col_First .. Col_First + 2 loop
>             if In_Grid (Row, Col).X = For_Value then
>                return False;
>             end if;
>          end loop;
>       end loop;
>       return True;
>    end Check_Block;