Helfer SpecialBits

Jan Burse, erstellt 15. Okt 2018
package jekmin.reference.misc;
import jekpro.model.inter.AbstractSpecial;
import jekpro.model.inter.Engine;
import jekpro.model.molec.BindCount;
import jekpro.model.molec.EngineMessage;
import jekpro.reference.arithmetic.SpecialEval;
import jekpro.tools.term.SkelCompound;
import java.math.BigInteger;
/**
* <p>Provides additional bitwise predicates.</p>
* <p/>
* Warranty & Liability
* To the extent permitted by applicable law and unless explicitly
* otherwise agreed upon, XLOG Technologies GmbH makes no warranties
* regarding the provided information. XLOG Technologies GmbH assumes
* no liability that any problems might be solved with the information
* provided by XLOG Technologies GmbH.
* <p/>
* Rights & License
* All industrial property rights regarding the information - copyright
* and patent rights in particular - are the sole property of XLOG
* Technologies GmbH. If the company was not the originator of some
* excerpts, XLOG Technologies GmbH has at least obtained the right to
* reproduce, change and translate the information.
* <p/>
* Reproduction is restricted to the whole unaltered document. Reproduction
* of the information is only allowed for non-commercial uses. Selling,
* giving away or letting of the execution of the library is prohibited.
* The library can be distributed as part of your applications and libraries
* for execution provided this comment remains unchanged.
* <p/>
* Restrictions
* Only to be distributed with programs that add significant and primary
* functionality to the library. Not to be distributed with additional
* software intended to replace any components of the library.
* <p/>
* Trademarks
* Jekejeke is a registered trademark of XLOG Technologies GmbH.
*/
public final class SpecialBits extends AbstractSpecial {
private final static int SPECIAL_TESTBIT = 0;
/**
* <p>Create a additional bitwise predicates.</p>
*
* @param i The id.
*/
public SpecialBits(int i) {
super(i);
}
/**
* <p>Logically evaluate a goal in a list of goals for the first time.</p>
* <p>The goal is passed via the skel and display of the engine.</p>
* <p>The continuation is passed via the r and u of the engine.</p>
* <p>The new continuation is returned via the skel and display of the engine.</p>
*
* @param en The engine.
* @return True if the predicate succeeded, otherwise false.
* @throws EngineMessage Shit happens.
*/
public final boolean moniFirst(Engine en)
throws EngineMessage {
try {
switch (id) {
case SPECIAL_TESTBIT:
Object[] temp = ((SkelCompound) en.skel).args;
BindCount[] ref = en.display;
Number alfa = SpecialEval.derefAndCastInteger(temp[0], ref);
SpecialEval.checkNotLessThanZero(alfa);
int k = SpecialEval.castIntValue(alfa);
Number beta = SpecialEval.derefAndCastInteger(temp[1], ref);
if (!sysTestBit(k, beta))
return false;
return en.getNextRaw();
default:
throw new IllegalArgumentException(OP_ILLEGAL_SPECIAL);
}
} catch (ClassCastException x) {
throw new EngineMessage(
EngineMessage.representationError(x.getMessage()));
}
}
/********************************************************************/
/* Additional Binary Number Built-in: */
/* sys_test_bit/3: sysTestBit() */
/********************************************************************/
/**
* <p>Test a bit.</p>
*
* @param k The first operand.
* @param b The second operand.
* @return The result.
*/
private static boolean sysTestBit(int k, Number b) {
if (b instanceof Integer) {
if (k <= 31) {
return (b.intValue() & (1 << k)) != 0;
} else {
return b.intValue() < 0;
}
} else {
return ((BigInteger) b).testBit(k);
}
}
}

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