Re: How can I make Reduce run from right to left?

[b.mcguinness747@gmail.com (Brian9000)]

I finally got an APL-like reduction using Ada Reduce:

pragma Ada_2022;
pragma Extensions_Allowed (On);

with Ada.Text_IO;

procedure Reverse_Reduction is
  type Real   is digits 15;
  type Vector is array(Natural range <>) of Real;

  data : constant Vector := [for i in 0 .. 11 => Real (i + 1)];

  function Minus (Accumulator : Real; Value : Real) return Real is
(Value - Accumulator);
begin
  for i in data'Range loop
    Ada.Text_IO.Put_Line (i'Image & ": " & data(i)'Image);
  end loop;

  Ada.Text_IO.New_Line;
  Ada.Text_IO.Put_Line (Real'Image ([ for i in 0 .. data'Last - 1 =>
data(data'Last - 1 - i) ]'Reduce(Minus, data(data'Last))));
end Reverse_Reduction;


$ ./reverse_reduction
 0:  1.00000000000000E+00
 1:  2.00000000000000E+00
 2:  3.00000000000000E+00
 3:  4.00000000000000E+00
 4:  5.00000000000000E+00
 5:  6.00000000000000E+00
 6:  7.00000000000000E+00
 7:  8.00000000000000E+00
 8:  9.00000000000000E+00
 9:  1.00000000000000E+01
 10:  1.10000000000000E+01
 11:  1.20000000000000E+01

-6.00000000000000E+00


In Gnu APL:

      ⍳12
1 2 3 4 5 6 7 8 9 10 11 12
      -/⍳12
¯6

--- Brian