values close to zero don't round nicely with bigdecs

src/main/java/carpet/script/value/NumericValue.java

@@ -15,6 +15,7 @@ import java.math.RoundingMode;
 import java.util.Locale;
 
 import static java.lang.Math.abs;
+import static java.lang.Math.signum;
 
 public class NumericValue extends Value
 {
@@ -57,6 +58,7 @@ public class NumericValue extends Value
         {
             if (value.isInfinite()) return "INFINITY";
             if (value.isNaN()) return "NaN";
+            if (abs(value) < epsilon) return (signum(value) < 0)?"-0":"0"; //zero rounding fails with big decimals
             // dobules have 16 point precision, 12 is plenty to display
             return BigDecimal.valueOf(value).round(displayRounding).stripTrailingZeros().toPlainString();
         }