46 lines
1.6 KiB
Java
46 lines
1.6 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 Power extends AbstractBinaryOperation {
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public Power(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 base, int exp) {
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if (exp < 0) throw new ArithmeticException("negative exponent");
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if (base == 0 && exp == 0) throw new ArithmeticException("zero to the power of zero");
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if (exp == 0) return 1;
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if (base == 0) return 0;
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int result = 1;
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int b = base;
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int e = exp;
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while (e > 0) {
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if ((e & 1) == 1) {
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result = checkedMul(result, b);
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}
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if (e > 1) b = checkedMul(b, b);
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e >>= 1;
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}
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return result;
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}
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private static int checkedMul(int a, int b) {
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if (a == 0 || b == 0) return 0;
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if (a == Integer.MIN_VALUE && b == -1) throw new OverflowException("power");
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if (b == Integer.MIN_VALUE && a == -1) throw new OverflowException("power");
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int result = a * b;
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if (result / a != b) throw new OverflowException("power");
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return result;
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}
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@Override protected BigInteger applyBi(BigInteger a, BigInteger b) { return a.pow(b.intValueExact()); }
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@Override protected BigDecimal applyBd(BigDecimal a, BigDecimal b) { return a.pow(b.intValueExact()); }
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} |