| ------------------------------------------------------------------------------ |
| -- -- |
| -- GNAT RUN-TIME COMPONENTS -- |
| -- -- |
| -- GNAT.BINARY_SEARCH -- |
| -- -- |
| -- B o d y -- |
| -- -- |
| -- Copyright (C) 2022, AdaCore -- |
| -- -- |
| -- GNAT is free software; you can redistribute it and/or modify it under -- |
| -- terms of the GNU General Public License as published by the Free Soft- -- |
| -- ware Foundation; either version 3, or (at your option) any later ver- -- |
| -- sion. GNAT is distributed in the hope that it will be useful, but WITH- -- |
| -- OUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY -- |
| -- or FITNESS FOR A PARTICULAR PURPOSE. -- |
| -- -- |
| -- As a special exception under Section 7 of GPL version 3, you are granted -- |
| -- additional permissions described in the GCC Runtime Library Exception, -- |
| -- version 3.1, as published by the Free Software Foundation. -- |
| -- -- |
| -- You should have received a copy of the GNU General Public License and -- |
| -- a copy of the GCC Runtime Library Exception along with this program; -- |
| -- see the files COPYING3 and COPYING.RUNTIME respectively. If not, see -- |
| -- <http://www.gnu.org/licenses/>. -- |
| ------------------------------------------------------------------------------ |
| |
| package body GNAT.Binary_Search is |
| |
| function Index |
| (First, Last, Start : Index_Type; |
| Element : Element_Type) return Index_Type'Base is |
| begin |
| if Leftmost then |
| declare |
| function Before |
| (Index : Index_Type; Element : Element_Type) return Boolean |
| is (Before (Get (Index), Element)) with Inline_Always; |
| |
| function Find is new Binary_Search.Leftmost |
| (Index_Type, Element_Type, Before); |
| begin |
| return Find (First, Last, Start, Element); |
| end; |
| |
| else |
| declare |
| function Before |
| (Element : Element_Type; Index : Index_Type) return Boolean |
| is (Before (Element, Get (Index))) with Inline_Always; |
| |
| function Find is new Rightmost (Index_Type, Element_Type, Before); |
| begin |
| return Find (First, Last, Start, Element); |
| end; |
| end if; |
| end Index; |
| |
| -------------- |
| -- Leftmost -- |
| -------------- |
| |
| function Leftmost |
| (First, Last, Start : Index_Type; |
| Element : Element_Type) return Index_Type'Base |
| is |
| L : Index_Type := First; |
| R : Index_Type := Index_Type'Succ (Last); |
| M : Index_Type := Start; |
| begin |
| if First <= Last then |
| loop |
| if Before (M, Element) then |
| L := Index_Type'Succ (M); |
| else |
| R := M; |
| end if; |
| |
| exit when L >= R; |
| |
| M := Index_Type'Val |
| (Index_Type'Pos (L) + |
| (Index_Type'Pos (R) - Index_Type'Pos (L)) / 2); |
| end loop; |
| end if; |
| |
| return L; |
| end Leftmost; |
| |
| --------------- |
| -- Rightmost -- |
| --------------- |
| |
| function Rightmost |
| (First, Last, Start : Index_Type; |
| Element : Element_Type) return Index_Type'Base |
| is |
| L : Index_Type := First; |
| R : Index_Type := Index_Type'Succ (Last); |
| M : Index_Type := Start; |
| begin |
| if First > Last then |
| return Last; |
| else |
| loop |
| if Before (Element, M) then |
| R := M; |
| else |
| L := Index_Type'Succ (M); |
| end if; |
| |
| exit when L >= R; |
| |
| M := Index_Type'Val |
| (Index_Type'Pos (L) + |
| (Index_Type'Pos (R) - Index_Type'Pos (L)) / 2); |
| end loop; |
| end if; |
| |
| return Index_Type'Pred (R); |
| end Rightmost; |
| |
| end GNAT.Binary_Search; |
