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Commit 9e855e82 authored by Hans Boehm's avatar Hans Boehm
Browse files

Fix decimal log(), rename positive_den() 

Bug: 20485102

The rational version of base 10 log(0) got into an infinite loop.

Change-Id: Id6263f7244c71260daa124e5eb4eea8592d0e6c7
parent c5e6e15b

src/com/android/calculator2/BoundedRational.java

+11 −10
Original line number Diff line number Diff line
@@ -65,7 +65,7 @@ public class BoundedRational { 
    // Output to user, more expensive, less useful for debugging

    // Not internationalized.

    public String toNiceString() {

        BoundedRational nicer = reduce().positive_den();

        BoundedRational nicer = reduce().positiveDen();

        String result = nicer.mNum.toString();

        if (!nicer.mDen.equals(BigInteger.ONE)) {

            result += "/" + nicer.mDen;
@@ -93,7 +93,7 @@ public class BoundedRational { 
    }



    // return an equivalent fraction with a positive denominator.

    private BoundedRational positive_den() {

    private BoundedRational positiveDen() {

        if (mDen.compareTo(BigInteger.ZERO) > 0) return this;

        return new BoundedRational(mNum.negate(), mDen.negate());

    }
@@ -109,7 +109,7 @@ public class BoundedRational { 
    // Return null if none exists.

    private BoundedRational maybeReduce() {

        if (!tooBig()) return this;

        BoundedRational result = positive_den();

        BoundedRational result = positiveDen();

        if (!result.tooBig()) return this;

        result = result.reduce();

        if (!result.tooBig()) return this;
@@ -186,7 +186,7 @@ public class BoundedRational { 
        // Return non-null if numerator and denominator are small perfect

        // squares.

        if (r == null) return null;

        r = r.positive_den().reduce();

        r = r.positiveDen().reduce();

        if (r.mNum.compareTo(BigInteger.ZERO) < 0) {

            throw new ArithmeticException("sqrt(negative)");

        }
@@ -384,19 +384,20 @@ public class BoundedRational { 
            return new BoundedRational(1);

        }

        if (base == null) return null;

        exp = exp.reduce().positive_den();

        exp = exp.reduce().positiveDen();

        if (!exp.mDen.equals(BigInteger.ONE)) return null;

        return base.pow(exp.mNum);

    }



    public static BoundedRational ln(BoundedRational r) {

        if (r != null && r.signum() < 0) {

            throw new ArithmeticException("log(negative)");

        if (r != null && r.signum() <= 0) {

            throw new ArithmeticException("log(non-positive)");

        }

        return map1to0(r);

    }



    // Return the base 10 log of n, if n is a power of 10, -1 otherwise.

    // n must be positive.

    private static long b10Log(BigInteger n) {

        // This algorithm is very naive, but we doubt it matters.

        long count = 0;
@@ -412,10 +413,10 @@ public class BoundedRational { 


    public static BoundedRational log(BoundedRational r) {

        if (r == null) return null;

        if (r.signum() < 0) {

            throw new ArithmeticException("log(negative)");

        if (r.signum() <= 0) {

            throw new ArithmeticException("log(non-positive)");

        }

        r = r.reduce();

        r = r.reduce().positiveDen();

        if (r == null) return null;

        if (r.mDen.equals(BigInteger.ONE)) {

            long log = b10Log(r.mNum);