46 lines
1.5 KiB
Java
46 lines
1.5 KiB
Java
package expression;
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import java.math.BigDecimal;
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import java.math.BigInteger;
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/**
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* @author Doschennikov Nikita (me@fymio.us)
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*/
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public class Log extends AbstractBinaryOperation {
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public Log(AbstractExpression l, AbstractExpression r) { super(l, r); }
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@Override protected String getOperator() { return "//"; }
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@Override protected int getPriority() { return 3; }
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@Override protected boolean isRightAssoc() { return true; }
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@Override
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protected int applyInt(int a, int b) {
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if (a <= 0) throw new ArithmeticException("logarithm of non-positive number");
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if (b <= 1) throw new ArithmeticException("logarithm base must be > 1");
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int result = 0;
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int power = 1;
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while (power <= a / b) {
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power *= b;
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result++;
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}
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return result;
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}
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@Override
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protected BigInteger applyBi(BigInteger a, BigInteger b) {
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if (a.signum() <= 0) throw new ArithmeticException("logarithm of non-positive number");
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if (b.compareTo(BigInteger.TWO) < 0) throw new ArithmeticException("logarithm base must be > 1");
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int result = 0;
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BigInteger power = BigInteger.ONE;
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while (power.multiply(b).compareTo(a) <= 0) {
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power = power.multiply(b);
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result++;
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}
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return BigInteger.valueOf(result);
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}
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@Override
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protected BigDecimal applyBd(BigDecimal a, BigDecimal b) {
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throw new UnsupportedOperationException("log not supported for BigDecimal");
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}
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} |