add signum

Signed-off-by: Mattias Andrée <maandree@operamail.com>

1 files changed, 89 insertions, 0 deletions

diff --git a/src/algorithms/bits/Signum.java b/src/algorithms/bits/Signum.java
new file mode 100644
index 0000000..647076c
--- /dev/null
+++ b/src/algorithms/bits/Signum.java
@@ -0,0 +1,89 @@
+/**
+ * Copyright © 2014  Mattias Andrée (maandree@member.fsf.org)
+ * 
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ * 
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Affero General Public License for more details.
+ * 
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+package algorithms.bits;
+
+import java.util.*;
+
+
+/**
+ * Compute the sign of an integer
+ */
+public class Signum
+{
+£<for T_S in byte_7 short_15 int_31 long_63; do
+  T=${T_S%_*}
+£>S=${T_S#*_}
+    /**
+     * Compute the sign of an integer
+     * 
+     * @param   value  The integer
+     * @return         {@code -1} if negative, otherwise {@code 0}
+     */
+    public static int minus_zero(£{T} value)
+    {
+	return (int)(value >> £{S});
+	/* In C, you can also do either of:
+	 *     -(value < 0)
+	 *     -(£{T})((unsigned £{T})((£{T})value) >> (sizeof(£{T}) * CHAR_BITS - 1));
+	 * The method used here is not portable in C
+	 * CHAR_BITS should be defined as 8 if not already defined
+	 */
+    }
+    
+    /**
+     * Compute the sign of an integer
+     * 
+     * @param   value  The integer
+     * @return         {@code -1} if negative, otherwise {@code 1}
+     */
+    public static int minus_plus(£{T} value)
+    {
+	return 1 | (int)(value >> £{S});
+    }
+    
+    /**
+     * Compute the sign of an integer
+     * 
+     * @param   value  The integer
+     * @return         {@code -1} if negative, {@code 1} if positive, and {@code 0} if zero
+     */
+    public static int minus_zero_plus(£{T} value)
+    {
+	return (int)(value >> £{S}) - (int)(-value >> £{S});
+	/* In C, you can also do either of:
+	 *     (value != 0) | -(£{T})((unsigned int)((£{T})value) >> (sizeof(£{T}) * CHAR_BITS - 1))
+	 *     (value != 0) | (value >> (sizeof(£{T}) * CHAR_BITS - 1))
+	 *     (value > 0) - (value < 0)
+	 */
+    }
+    
+    /**
+     * Compute the sign of an integer
+     * 
+     * @param   value  The integer
+     * @return         {@code 0} if negative, otherwise {@code 1}
+     */
+    public static int zero_plus(£{T} value)
+    {
+	return 1 ^ (1 & (int)(value >> £{S}));
+	/* In C, you can also do:
+	 *     1 ^ ((unsigned £{T})value >> (sizeof(£{T}) * CHAR_BITS - 1))
+	 */
+    }
+£>done
+}
+