Use bool(Bitboard b) instead of !!b (#1321)

The idiom !!b is confusing newcomers (e.g. Stefan needs explaining here https://groups.google.com/d/msg/fishcooking/vYqnsRI4brY/Gaf60QuACwAJ).

No functional change.

src/bitboard.h

@@ -130,7 +130,6 @@ constexpr bool more_than_one(Bitboard b) {
   return b & (b - 1);
 }
 
-
 /// rank_bb() and file_bb() return a bitboard representing all the squares on
 /// the given file or rank.
 

src/evaluate.cpp

@@ -342,12 +342,12 @@ namespace {
             // Bonus for outpost squares
             bb = OutpostRanks & ~pe->pawn_attacks_span(Them);
             if (bb & s)
-                score += Outpost[Pt == BISHOP][!!(attackedBy[Us][PAWN] & s)] * 2;
+                score += Outpost[Pt == BISHOP][bool(attackedBy[Us][PAWN] & s)] * 2;
             else
             {
                 bb &= b & ~pos.pieces(Us);
                 if (bb)
-                   score += Outpost[Pt == BISHOP][!!(attackedBy[Us][PAWN] & bb)];
+                   score += Outpost[Pt == BISHOP][bool(attackedBy[Us][PAWN] & bb)];
             }
 
             // Bonus when behind a pawn
@@ -388,7 +388,7 @@ namespace {
 
             // Bonus when on an open or semi-open file
             if (pe->semiopen_file(Us, file_of(s)))
-                score += RookOnFile[!!pe->semiopen_file(Them, file_of(s))];
+                score += RookOnFile[bool(pe->semiopen_file(Them, file_of(s)))];
 
             // Penalty when trapped by the king, even more if the king cannot castle
             else if (mob <= 3)
@@ -450,7 +450,7 @@ namespace {
         kingDanger =        kingAttackersCount[Them] * kingAttackersWeight[Them]
                     + 102 * kingAdjacentZoneAttacksCount[Them]
                     + 191 * popcount(kingRing[Us] & weak)
-                    + 143 * !!pos.pinned_pieces(Us)
+                    + 143 * bool(pos.pinned_pieces(Us))
                     - 848 * !pos.count<QUEEN>(Them)
                     -   9 * mg_value(score) / 8
                     +  40;

src/pawns.cpp

@@ -174,7 +174,7 @@ namespace {
 
         // Score this pawn
         if (supported | phalanx)
-            score += Connected[opposed][!!phalanx][popcount(supported)][relative_rank(Us, s)];
+            score += Connected[opposed][bool(phalanx)][popcount(supported)][relative_rank(Us, s)];
 
         else if (!neighbours)
             score -= Isolated, e->weakUnopposed[Us] += !opposed;

src/pawns.h

@@ -50,7 +50,7 @@ struct Entry {
   }
 
   int pawns_on_same_color_squares(Color c, Square s) const {
-    return pawnsOnSquares[c][!!(DarkSquares & s)];
+    return pawnsOnSquares[c][bool(DarkSquares & s)];
   }
 
   template<Color Us>

src/search.cpp

@@ -1115,7 +1115,7 @@ moves_loop: // When in check search starts from here
 
     const bool PvNode = NT == PV;
 
-    assert(InCheck == !!pos.checkers());
+    assert(InCheck == bool(pos.checkers()));
     assert(alpha >= -VALUE_INFINITE && alpha < beta && beta <= VALUE_INFINITE);
     assert(PvNode || (alpha == beta - 1));
     assert(depth <= DEPTH_ZERO);