Simplify backward pawn definition

Make use of 'lever' attribute

No functional change

Resolves #234

diff --git a/src/pawns.cpp b/src/pawns.cpp
index eda707ff97dac85d51e8c68aa897cf0bd918af9e..798bc0a070319dc846986535e4480d9e3442d349 100644 (file)
--- a/src/pawns.cpp
+++ b/src/pawns.cpp
@@ -144,12 +144,11 @@ namespace {
         lever       =   theirPawns & pawnAttacksBB[s];
 
         // Test for backward pawn.
-        // If the pawn is passed, isolated, or connected it cannot be
+        // If the pawn is passed, isolated, connected or a lever it cannot be
         // backward. If there are friendly pawns behind on adjacent files
-        // or if it can capture an enemy pawn it cannot be backward either.
-        if (   (passed | isolated | connected)
-            || (ourPawns & pawn_attack_span(Them, s))
-            || (pos.attacks_from<PAWN>(s, Us) & theirPawns))
+        // it cannot be backward either.
+        if (   (passed | isolated | connected | lever)
+            || (ourPawns & pawn_attack_span(Them, s)))
             backward = false;
         else
         {