From e154a158a9f77ef686f99b6aa873980d0fca0650 Mon Sep 17 00:00:00 2001
From: James Roseborough <james.roseborough@luaj.org>
Date: Sat, 22 Sep 2007 05:25:02 +0000
Subject: [PATCH] Add ipow, to compute power for integers.

---
 src/main/java/lua/value/LDouble.java  | 25 ++++++++++++++++++++++---
 src/main/java/lua/value/LInteger.java | 10 +++++++++-
 2 files changed, 31 insertions(+), 4 deletions(-)

diff --git a/src/main/java/lua/value/LDouble.java b/src/main/java/lua/value/LDouble.java
index 78909248..2613f8f7 100644
--- a/src/main/java/lua/value/LDouble.java
+++ b/src/main/java/lua/value/LDouble.java
@@ -52,12 +52,31 @@ public class LDouble extends LNumber {
 		case Lua.OP_MUL: return new LDouble( lhs * rhs );
 		case Lua.OP_DIV: return new LDouble( lhs / rhs );
 		case Lua.OP_MOD: return new LDouble( lhs - Math.floor(lhs/rhs) * rhs );
-		
-//		case Lua.OP_POW: return new LDouble( Math.pow(lhs, rhs) );
+		// case Lua.OP_POW: return new LDouble( dpow(lhs, rhs) );
 		}
 		return luaUnsupportedOperation();
 	}
-	
+
+	/*
+	public static double dpow(double a, double b) {
+		if ( b < 0 )
+			return 1 / dpow( a, -b );
+		int p = 1;
+		int whole = (int) b;
+		for ( double v=a; whole > 0; whole>>=1, v=v*v )
+			if ( (whole & 1) != 0 )
+				p *= v;
+		int frac = (int) (0x10000 * b);
+		for ( ; (frac&0xffff)!=0; frac<<=1 ) {
+			a = Math.sqrt(a);
+			if ( (frac & 0x8000) != 0 )
+				p *= a;
+		}
+		return p;
+	}
+	*/
+
+
 	public int luaAsInt() {
 		return (int) m_value;
 	}
diff --git a/src/main/java/lua/value/LInteger.java b/src/main/java/lua/value/LInteger.java
index 16c4a5ad..eb866e9d 100644
--- a/src/main/java/lua/value/LInteger.java
+++ b/src/main/java/lua/value/LInteger.java
@@ -43,11 +43,19 @@ public class LInteger extends LNumber {
 		case Lua.OP_MUL: return new LInteger( m_value * rhs );
 		case Lua.OP_DIV: return new LInteger( m_value / rhs );
 		case Lua.OP_MOD: return new LInteger( m_value - ((int) Math.floor(m_value/(double)rhs)) * rhs );
-//		case Lua.OP_POW: return new LInteger( (int) Math.pow(m_value, rhs) );
+		case Lua.OP_POW: return new LInteger( ipow(m_value, rhs) );
 		}
 		return luaUnsupportedOperation();
 	}
 	
+	private static int ipow(int v, int rhs) {
+		int p = 1;
+		for ( ; rhs > 0; rhs>>=1, v=v*v )
+			if ( (rhs & 1) != 0 )
+				p *= v;
+		return p;
+	}
+
 	// binary operations on mixed integer, double
 	public LValue luaBinOpDouble(int opcode, double rhs) {
 		return LDouble.luaBinOpDoubleDouble(opcode, (double) m_value, rhs );