1 files changed, 219 insertions, 0 deletions
diff --git a/src/main/java/ch/obermuhlner/math/big/stream/BigDecimalStream.java b/src/main/java/ch/obermuhlner/math/big/stream/BigDecimalStream.java
new file mode 100644
index 0000000000..05a45fd846
--- /dev/null
+++ b/src/main/java/ch/obermuhlner/math/big/stream/BigDecimalStream.java
@@ -0,0 +1,219 @@
+package ch.obermuhlner.math.big.stream;
+
+import java.math.BigDecimal;
+import java.math.MathContext;
+import java.util.Comparator;
+import java.util.Spliterator;
+import java.util.Spliterators.AbstractSpliterator;
+import java.util.function.Consumer;
+import java.util.stream.Stream;
+import java.util.stream.StreamSupport;
+
+import ch.obermuhlner.math.big.BigDecimalMath;
+
+/**
+ * Provides constructor methods for streams of {@link BigDecimal} elements. 
+ */
+public class BigDecimalStream {
+
+    /**
+     * Returns a sequential ordered {@code Stream<BigDecimal>} from {@code startInclusive}
+     * (inclusive) to {@code endExclusive} (exclusive) by an incremental {@code step}.
+     *
+     * <p>An equivalent sequence of increasing values can be produced
+     * sequentially using a {@code for} loop as follows:
+     * <pre>for (BigDecimal i = startInclusive; i.compareTo(endExclusive) &lt; 0; i = i.add(step, mathContext)) {
+    // ...
+}</pre>
+     *
+     * @param startInclusive the (inclusive) initial value
+     * @param endExclusive the exclusive upper bound
+     * @param step the step between elements
+     * @param mathContext the {@link MathContext} used for all mathematical operations
+     * @return a sequential {@code Stream<BigDecimal>}
+     */
+    public static Stream<BigDecimal> range(BigDecimal startInclusive, BigDecimal endExclusive, BigDecimal step, MathContext mathContext) {
+    	if (step.signum() == 0) {
+    		throw new IllegalArgumentException("invalid step: 0");
+    	}
+		if (endExclusive.subtract(startInclusive).signum() != step.signum()) {
+			return Stream.empty();
+		}
+    	return StreamSupport.stream(new BigDecimalSpliterator(startInclusive, endExclusive, false, step, mathContext), false);
+    }
+
+    /**
+     * Returns a sequential ordered {@code Stream<BigDecimal>} from {@code startInclusive}
+     * (inclusive) to {@code endExclusive} (exclusive) by an incremental {@code step}.
+     * 
+     * <p>The {@code long} arguments are converted using {@link BigDecimal#valueOf(long)}.</p>
+     * 
+     * @param startInclusive the (inclusive) initial value
+     * @param endExclusive the exclusive upper bound
+     * @param step the step between elements
+     * @param mathContext the {@link MathContext} used for all mathematical operations
+     * @return a sequential {@code Stream<BigDecimal>}
+     * @see #range(BigDecimal, BigDecimal, BigDecimal, MathContext)
+     */
+    public static Stream<BigDecimal> range(long startInclusive, long endExclusive, long step, MathContext mathContext) {
+    	return range(BigDecimal.valueOf(startInclusive), BigDecimal.valueOf(endExclusive), BigDecimal.valueOf(step), mathContext);
+    }
+
+    /**
+     * Returns a sequential ordered {@code Stream<BigDecimal>} from {@code startInclusive}
+     * (inclusive) to {@code endExclusive} (exclusive) by an incremental {@code step}.
+     * 
+     * <p>The {@code double} arguments are converted using {@link BigDecimal#valueOf(double)}.</p>
+     * 
+     * @param startInclusive the (inclusive) initial value
+     * @param endExclusive the exclusive upper bound
+     * @param step the step between elements
+     * @param mathContext the {@link MathContext} used for all mathematical operations
+     * @return a sequential {@code Stream<BigDecimal>}
+     * @see #range(BigDecimal, BigDecimal, BigDecimal, MathContext)
+     */
+    public static Stream<BigDecimal> range(double startInclusive, double endExclusive, double step, MathContext mathContext) {
+    	return range(BigDecimal.valueOf(startInclusive), BigDecimal.valueOf(endExclusive), BigDecimal.valueOf(step), mathContext);
+    }
+    
+    /**
+     * Returns a sequential ordered {@code Stream<BigDecimal>} from {@code startInclusive}
+     * (inclusive) to {@code endInclusive} (inclusive) by an incremental {@code step}.
+     *
+     * <p>An equivalent sequence of increasing values can be produced
+     * sequentially using a {@code for} loop as follows:
+     * <pre>for (BigDecimal i = startInclusive; i.compareTo(endInclusive) &lt;= 0; i = i.add(step, mathContext)) {
+    // ...
+}</pre>
+     *
+     * @param startInclusive the (inclusive) initial value
+     * @param endInclusive the inclusive upper bound
+     * @param step the step between elements
+     * @param mathContext the {@link MathContext} used for all mathematical operations
+     * @return a sequential {@code Stream<BigDecimal>}
+     * @see #range(BigDecimal, BigDecimal, BigDecimal, MathContext)
+     */
+    public static Stream<BigDecimal> rangeClosed(BigDecimal startInclusive, BigDecimal endInclusive, BigDecimal step, MathContext mathContext) {
+    	if (step.signum() == 0) {
+    		throw new IllegalArgumentException("invalid step: 0");
+    	}
+		if (endInclusive.subtract(startInclusive).signum() == -step.signum()) {
+			return Stream.empty();
+		}
+    	return StreamSupport.stream(new BigDecimalSpliterator(startInclusive, endInclusive, true, step, mathContext), false);
+    }
+
+    /**
+     * Returns a sequential ordered {@code Stream<BigDecimal>} from {@code startInclusive}
+     * (inclusive) to {@code endInclusive} (inclusive) by an incremental {@code step}.
+     *
+     * <p>The {@code long} arguments are converted using {@link BigDecimal#valueOf(long)}.</p>
+     * 
+     * @param startInclusive the (inclusive) initial value
+     * @param endInclusive the inclusive upper bound
+     * @param step the step between elements
+     * @param mathContext the {@link MathContext} used for all mathematical operations
+     * @return a sequential {@code Stream<BigDecimal>}
+     * @see #rangeClosed(BigDecimal, BigDecimal, BigDecimal, MathContext)
+     */
+    public static Stream<BigDecimal> rangeClosed(long startInclusive, long endInclusive, long step, MathContext mathContext) {
+    	return rangeClosed(BigDecimal.valueOf(startInclusive), BigDecimal.valueOf(endInclusive), BigDecimal.valueOf(step), mathContext);
+    }
+
+    /**
+     * Returns a sequential ordered {@code Stream<BigDecimal>} from {@code startInclusive}
+     * (inclusive) to {@code endInclusive} (inclusive) by an incremental {@code step}.
+     *
+     * <p>The {@code double} arguments are converted using {@link BigDecimal#valueOf(double)}.</p>
+     * 
+     * @param startInclusive the (inclusive) initial value
+     * @param endInclusive the inclusive upper bound
+     * @param step the step between elements
+     * @param mathContext the {@link MathContext} used for all mathematical operations
+     * @return a sequential {@code Stream<BigDecimal>}
+     * @see #rangeClosed(BigDecimal, BigDecimal, BigDecimal, MathContext)
+     */
+    public static Stream<BigDecimal> rangeClosed(double startInclusive, double endInclusive, double step, MathContext mathContext) {
+    	return rangeClosed(BigDecimal.valueOf(startInclusive), BigDecimal.valueOf(endInclusive), BigDecimal.valueOf(step), mathContext);
+    }
+
+    private static class BigDecimalSpliterator extends AbstractSpliterator<BigDecimal> {
+
+		private BigDecimal value;
+		private BigDecimal step;
+		private long count;
+		private MathContext mathContext;
+
+		public BigDecimalSpliterator(BigDecimal startInclusive, BigDecimal step, long count, MathContext mathContext) {
+    		super(count,
+    				Spliterator.SIZED | Spliterator.SUBSIZED | Spliterator.DISTINCT | Spliterator.IMMUTABLE | Spliterator.NONNULL | Spliterator.ORDERED | Spliterator.SORTED);
+			
+    		this.value = startInclusive;
+			this.step = step;
+			this.count = count;
+			this.mathContext = mathContext;
+		}
+    	
+		public BigDecimalSpliterator(BigDecimal startInclusive, BigDecimal end, boolean inclusive, BigDecimal step, MathContext mathContext) {
+			this(startInclusive, step, estimatedCount(startInclusive, end, inclusive, step, mathContext), mathContext);
+		}
+		
+		private static long estimatedCount(BigDecimal startInclusive, BigDecimal end, boolean inclusive, BigDecimal step, MathContext mathContext) {
+			BigDecimal count = end.subtract(startInclusive).divide(step, mathContext);
+    		long result = count.longValue();
+    		if (BigDecimalMath.fractionalPart(count).signum() != 0) {
+    			result++;
+    		} else {
+    			if (inclusive) {
+    				result++;
+    			}
+    		}
+    		return result;
+		}
+
+		@Override
+		public Comparator<? super BigDecimal> getComparator() {
+			if (step.signum() < 0) {
+				return Comparator.reverseOrder();
+			}
+			return null;
+		}
+		
+		@Override
+		public boolean tryAdvance(Consumer<? super BigDecimal> action) {
+			if (count == 0) {
+				return false;
+			}
+			
+			action.accept(value);
+			value = value.add(step, mathContext);
+			count--;
+			return true;
+		}
+		
+		@Override
+		public void forEachRemaining(Consumer<? super BigDecimal> action) {
+			while (count > 0) {
+				action.accept(value);
+				value = value.add(step, mathContext);
+				count--;
+			}
+		}
+		
+		@Override
+		public Spliterator<BigDecimal> trySplit() {
+			long firstHalfCount = count / 2;
+			
+			if (firstHalfCount == 0) {
+				return null;
+			}
+			
+			long secondHalfCount = count - firstHalfCount;
+			
+			count = firstHalfCount;
+			BigDecimal startSecondHalf = value.add(step.multiply(new BigDecimal(firstHalfCount), mathContext), mathContext);
+			
+			return new BigDecimalSpliterator(startSecondHalf, step, secondHalfCount, mathContext);
+		}
+    }
+}