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/**
* 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;
/**
* Signum operations on integers
*/
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))
*/
}
/**
* Detect if two integers have opposite signs
*
* @param a One of the integers
* @param b The other of the integers
* @return {@code true} iff either {@code a} or {@code b} is negative and the other is positive
*/
public static boolean haveOpposite(£{T} a, £{T} b)
{
return (£{T})(a ^ b) < 0;
}
/**
* Negates a value of a flag is set to 1
*
* @param value The value
* @param flag The flag, must be either 1 or 0
* @return {@code flag == 1 ? value : -value}
*/
public static £{T} negateOn1(£{T} value, £{T} flag)
{
return (£{T})((£{T})(flag ^ (flag - 1)) * value);
}
/**
* Negates a value of a flag is set to 1
*
* @param value The value
* @param flag The flag, must be either 1 or 0
* @return {@code flag == 0 ? value : -value}
*/
public static £{T} negateOn0(£{T} value, £{T} flag)
{
return (£{T})((£{T})(value ^ -flag) + flag);
}
£>done
}
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