From f21b50398231b4846c364e23bfeeab314c7731ea Mon Sep 17 00:00:00 2001
From: Joost VandeVondele <Joost.VandeVondele@gmail.com>
Date: Thu, 18 Apr 2019 16:53:52 +0200
Subject: [PATCH] Simplify distance (#2109)

Only called with Squares as argument, so remove unused variants.

As this is just syntax changes, only verified bench at high depth.

No functional change.
---
 src/bitboard.h  | 10 ++++------
 src/endgame.cpp |  4 +---
 2 files changed, 5 insertions(+), 9 deletions(-)

diff --git a/src/bitboard.h b/src/bitboard.h
index b1d961f4..6f99ef19 100644
--- a/src/bitboard.h
+++ b/src/bitboard.h
@@ -237,15 +237,13 @@ inline bool aligned(Square s1, Square s2, Square s3) {
 
 
 /// distance() functions return the distance between x and y, defined as the
-/// number of steps for a king in x to reach y. Works with squares, ranks, files.
+/// number of steps for a king in x to reach y.
 
-template<typename T> inline int distance(T x, T y) { return std::abs(x - y); }
+template<typename T1 = Square> inline int distance(Square x, Square y);
+template<> inline int distance<File>(Square x, Square y) { return std::abs(file_of(x) - file_of(y)); }
+template<> inline int distance<Rank>(Square x, Square y) { return std::abs(rank_of(x) - rank_of(y)); }
 template<> inline int distance<Square>(Square x, Square y) { return SquareDistance[x][y]; }
 
-template<typename T1, typename T2> inline int distance(T2 x, T2 y);
-template<> inline int distance<File>(Square x, Square y) { return distance(file_of(x), file_of(y)); }
-template<> inline int distance<Rank>(Square x, Square y) { return distance(rank_of(x), rank_of(y)); }
-
 template<class T> constexpr const T& clamp(const T& v, const T& lo, const T&  hi) {
   return v < lo ? lo : v > hi ? hi : v;
 }
diff --git a/src/endgame.cpp b/src/endgame.cpp
index efc41a98..5958e633 100644
--- a/src/endgame.cpp
+++ b/src/endgame.cpp
@@ -635,8 +635,6 @@ ScaleFactor Endgame<KBPPKB>::operator()(const Position& pos) const {
   Square ksq = pos.square<KING>(weakSide);
   Square psq1 = pos.squares<PAWN>(strongSide)[0];
   Square psq2 = pos.squares<PAWN>(strongSide)[1];
-  Rank r1 = rank_of(psq1);
-  Rank r2 = rank_of(psq2);
   Square blockSq1, blockSq2;
 
   if (relative_rank(strongSide, psq1) > relative_rank(strongSide, psq2))
@@ -670,7 +668,7 @@ ScaleFactor Endgame<KBPPKB>::operator()(const Position& pos) const {
         && opposite_colors(ksq, wbsq)
         && (   bbsq == blockSq2
             || (pos.attacks_from<BISHOP>(blockSq2) & pos.pieces(weakSide, BISHOP))
-            || distance(r1, r2) >= 2))
+            || distance<Rank>(psq1, psq2) >= 2))
         return SCALE_FACTOR_DRAW;
 
     else if (   ksq == blockSq2
-- 
2.39.2