diff --git a/asterix-app/src/test/resources/runtimets/queries/string/matches11.aql b/asterix-app/src/test/resources/runtimets/queries/string/matches11.aql
index 1e96b5f..8b9d3be 100644
--- a/asterix-app/src/test/resources/runtimets/queries/string/matches11.aql
+++ b/asterix-app/src/test/resources/runtimets/queries/string/matches11.aql
@@ -11,6 +11,8 @@
 matches("hello","helllo"),
 matches("hello"," "),
 matches(null,"hello"),
+matches(null, ""),
+matches(null, null),
 matches("hello","[^a-z]")]
 return $a
 
diff --git a/asterix-app/src/test/resources/runtimets/queries/string/replace1.aql b/asterix-app/src/test/resources/runtimets/queries/string/replace1.aql
index 3a9e932..419fe4b 100644
--- a/asterix-app/src/test/resources/runtimets/queries/string/replace1.aql
+++ b/asterix-app/src/test/resources/runtimets/queries/string/replace1.aql
@@ -7,4 +7,6 @@
 let $c1 := replace("abracadabra", "a", "")
 let $c2 := replace("abracadabra", "a(.)", "a$1$1")
 let $c3 := replace("darted", "^(.*?)d(.*)$", "$1c$2")
-return {"result1": $c1, "result2": $c2, "result3": $c3}
+let $c4 := replace("hello", "", "-")
+let $c5 := replace(null, "*", "-")
+return {"result1": $c1, "result2": $c2, "result3": $c3, "result4": $c4, "result5": $c5}
diff --git a/asterix-app/src/test/resources/runtimets/results/string/matches11.adm b/asterix-app/src/test/resources/runtimets/results/string/matches11.adm
index 440a996..65ffc69 100644
--- a/asterix-app/src/test/resources/runtimets/results/string/matches11.adm
+++ b/asterix-app/src/test/resources/runtimets/results/string/matches11.adm
@@ -3,3 +3,5 @@
 false
 false
 false
+true
+false
diff --git a/asterix-app/src/test/resources/runtimets/results/string/replace1.adm b/asterix-app/src/test/resources/runtimets/results/string/replace1.adm
index 5f992ce..24d401c 100644
--- a/asterix-app/src/test/resources/runtimets/results/string/replace1.adm
+++ b/asterix-app/src/test/resources/runtimets/results/string/replace1.adm
@@ -1 +1 @@
-{ "result1": "brcdbr", "result2": "abbraccaddabbra", "result3": "carted" }
+{ "result1": "brcdbr", "result2": "abbraccaddabbra", "result3": "carted", "result4": "-h-e-l-l-o-", "result5": null }
diff --git a/asterix-app/src/test/resources/runtimets/results/string/string-equal-true1.adm b/asterix-app/src/test/resources/runtimets/results/string/string-equal-true1.adm
deleted file mode 100644
index ea9ca72..0000000
--- a/asterix-app/src/test/resources/runtimets/results/string/string-equal-true1.adm
+++ /dev/null
@@ -1 +0,0 @@
-{ "result1": false }
diff --git a/asterix-runtime/src/main/java/edu/uci/ics/asterix/runtime/evaluators/functions/CodePointToStringDescriptor.java b/asterix-runtime/src/main/java/edu/uci/ics/asterix/runtime/evaluators/functions/CodePointToStringDescriptor.java
index 5dcb838..55fe563 100644
--- a/asterix-runtime/src/main/java/edu/uci/ics/asterix/runtime/evaluators/functions/CodePointToStringDescriptor.java
+++ b/asterix-runtime/src/main/java/edu/uci/ics/asterix/runtime/evaluators/functions/CodePointToStringDescriptor.java
@@ -93,9 +93,6 @@
                     private ICopyEvaluatorFactory listEvalFactory = args[0];
                     private ArrayBackedValueStorage outInputList = new ArrayBackedValueStorage();
                     private ICopyEvaluator evalList = listEvalFactory.createEvaluator(outInputList);
-                    @SuppressWarnings("unchecked")
-                    private ISerializerDeserializer<ANull> nullSerde = AqlSerializerDeserializerProvider.INSTANCE
-                            .getSerializerDeserializer(BuiltinType.ANULL);
 
                     @Override
                     public void evaluate(IFrameTupleReference tuple) throws AlgebricksException {
@@ -103,10 +100,6 @@
                             outInputList.reset();
                             evalList.evaluate(tuple);
                             byte[] serOrderedList = outInputList.getByteArray();
-                            if (serOrderedList[0] == SER_NULL_TYPE_TAG) {
-                                nullSerde.serialize(ANull.NULL, out);
-                                return;
-                            }
                             if (serOrderedList[0] != SER_ORDEREDLIST_TYPE_TAG) {
                                 throw new AlgebricksException("Expects an Integer List."
                                         + EnumDeserializer.ATYPETAGDESERIALIZER.deserialize(serOrderedList[0]));
diff --git a/asterix-runtime/src/main/java/edu/uci/ics/asterix/runtime/evaluators/functions/NumericRoundHalfToEven2Descriptor.java b/asterix-runtime/src/main/java/edu/uci/ics/asterix/runtime/evaluators/functions/NumericRoundHalfToEven2Descriptor.java
index 06cf69a..e205bf5 100644
--- a/asterix-runtime/src/main/java/edu/uci/ics/asterix/runtime/evaluators/functions/NumericRoundHalfToEven2Descriptor.java
+++ b/asterix-runtime/src/main/java/edu/uci/ics/asterix/runtime/evaluators/functions/NumericRoundHalfToEven2Descriptor.java
@@ -98,13 +98,10 @@
                             return (int) AInt32SerializerDeserializer.getInt(argOut.getByteArray(), 1);
                         } else if (argOut.getByteArray()[0] == serInt64TypeTag) {
                             return (int) AInt64SerializerDeserializer.getLong(argOut.getByteArray(), 1);
-                        } else if (argOut.getByteArray()[0] == serFloatTypeTag) {
-                            return (int) AFloatSerializerDeserializer.getFloat(argOut.getByteArray(), 1);
-                        } else if (argOut.getByteArray()[0] == serDoubleTypeTag) {
-                            return (int) ADoubleSerializerDeserializer.getDouble(argOut.getByteArray(), 1);
+                        } else {
+                            throw new AlgebricksException(
+                                    "The precision argument for round-half-to-even should be an integer.");
                         }
-
-                        return 0;
                     }
 
                     @SuppressWarnings("unchecked")
diff --git a/asterix-runtime/src/main/java/edu/uci/ics/asterix/runtime/evaluators/functions/StringConcatDescriptor.java b/asterix-runtime/src/main/java/edu/uci/ics/asterix/runtime/evaluators/functions/StringConcatDescriptor.java
index f975579..f53ebe8 100644
--- a/asterix-runtime/src/main/java/edu/uci/ics/asterix/runtime/evaluators/functions/StringConcatDescriptor.java
+++ b/asterix-runtime/src/main/java/edu/uci/ics/asterix/runtime/evaluators/functions/StringConcatDescriptor.java
@@ -4,7 +4,6 @@
 import java.io.IOException;
 
 import edu.uci.ics.asterix.common.exceptions.AsterixException;
-import edu.uci.ics.asterix.common.functions.FunctionConstants;
 import edu.uci.ics.asterix.formats.nontagged.AqlSerializerDeserializerProvider;
 import edu.uci.ics.asterix.om.base.ANull;
 import edu.uci.ics.asterix.om.functions.AsterixBuiltinFunctions;
@@ -67,10 +66,6 @@
                             } catch (AsterixException e) {
                                 throw new AlgebricksException(e);
                             }
-                            if (listAccessor.getItemType() == ATypeTag.NULL) {
-                                nullSerde.serialize(ANull.NULL, out);
-                                return;
-                            }
                             try {
                                 // calculate length first
                                 int utf8Len = 0;
diff --git a/asterix-runtime/src/main/java/edu/uci/ics/asterix/runtime/evaluators/functions/StringJoinDescriptor.java b/asterix-runtime/src/main/java/edu/uci/ics/asterix/runtime/evaluators/functions/StringJoinDescriptor.java
index c379c3e3..67334ce 100644
--- a/asterix-runtime/src/main/java/edu/uci/ics/asterix/runtime/evaluators/functions/StringJoinDescriptor.java
+++ b/asterix-runtime/src/main/java/edu/uci/ics/asterix/runtime/evaluators/functions/StringJoinDescriptor.java
@@ -5,20 +5,16 @@
 
 import edu.uci.ics.asterix.common.exceptions.AsterixException;
 import edu.uci.ics.asterix.dataflow.data.nontagged.serde.AOrderedListSerializerDeserializer;
-import edu.uci.ics.asterix.formats.nontagged.AqlSerializerDeserializerProvider;
-import edu.uci.ics.asterix.om.base.ANull;
 import edu.uci.ics.asterix.om.functions.AsterixBuiltinFunctions;
 import edu.uci.ics.asterix.om.functions.IFunctionDescriptor;
 import edu.uci.ics.asterix.om.functions.IFunctionDescriptorFactory;
 import edu.uci.ics.asterix.om.types.ATypeTag;
-import edu.uci.ics.asterix.om.types.BuiltinType;
 import edu.uci.ics.asterix.om.types.EnumDeserializer;
 import edu.uci.ics.asterix.runtime.evaluators.base.AbstractScalarFunctionDynamicDescriptor;
 import edu.uci.ics.hyracks.algebricks.common.exceptions.AlgebricksException;
 import edu.uci.ics.hyracks.algebricks.core.algebra.functions.FunctionIdentifier;
 import edu.uci.ics.hyracks.algebricks.runtime.base.ICopyEvaluator;
 import edu.uci.ics.hyracks.algebricks.runtime.base.ICopyEvaluatorFactory;
-import edu.uci.ics.hyracks.api.dataflow.value.ISerializerDeserializer;
 import edu.uci.ics.hyracks.data.std.api.IDataOutputProvider;
 import edu.uci.ics.hyracks.data.std.primitive.UTF8StringPointable;
 import edu.uci.ics.hyracks.data.std.util.ArrayBackedValueStorage;
@@ -37,7 +33,6 @@
         }
     };
     private final static byte SER_STRING_TYPE_TAG = ATypeTag.STRING.serialize();
-    private final static byte SER_NULL_TYPE_TAG = ATypeTag.NULL.serialize();
     private final static byte SER_ORDEREDLIST_TYPE_TAG = ATypeTag.ORDEREDLIST.serialize();
     private final byte stringTypeTag = ATypeTag.STRING.serialize();
 
@@ -58,9 +53,6 @@
                     private ArrayBackedValueStorage outInputSep = new ArrayBackedValueStorage();
                     private ICopyEvaluator evalList = listEvalFactory.createEvaluator(outInputList);
                     private ICopyEvaluator evalSep = sepEvalFactory.createEvaluator(outInputSep);
-                    @SuppressWarnings("unchecked")
-                    private ISerializerDeserializer<ANull> nullSerde = AqlSerializerDeserializerProvider.INSTANCE
-                            .getSerializerDeserializer(BuiltinType.ANULL);
 
                     @Override
                     public void evaluate(IFrameTupleReference tuple) throws AlgebricksException {
@@ -72,20 +64,14 @@
                             outInputSep.reset();
                             evalSep.evaluate(tuple);
                             byte[] serSep = outInputSep.getByteArray();
-                            if (serOrderedList[0] == SER_NULL_TYPE_TAG) {
-                                nullSerde.serialize(ANull.NULL, out);
-                                return;
-                            }
                             if (serOrderedList[0] != SER_ORDEREDLIST_TYPE_TAG) {
-                                throw new AlgebricksException("Expects String List."
+                                throw new AlgebricksException("Expects String List but got "
                                         + EnumDeserializer.ATYPETAGDESERIALIZER.deserialize(serOrderedList[0]));
                             }
 
-                            if (serSep[0] == SER_NULL_TYPE_TAG) {
-                            }
                             if (serSep[0] != SER_STRING_TYPE_TAG) {
-                                throw new AlgebricksException("Expects String as Seperator."
-                                        + EnumDeserializer.ATYPETAGDESERIALIZER.deserialize(serOrderedList[0]));
+                                throw new AlgebricksException("Expects String as Seperator but got "
+                                        + EnumDeserializer.ATYPETAGDESERIALIZER.deserialize(serSep[0]));
                             }
 
                             int size = AOrderedListSerializerDeserializer.getNumberOfItems(serOrderedList);
diff --git a/asterix-runtime/src/main/java/edu/uci/ics/asterix/runtime/evaluators/functions/StringToCodePointDescriptor.java b/asterix-runtime/src/main/java/edu/uci/ics/asterix/runtime/evaluators/functions/StringToCodePointDescriptor.java
index fdd45e2..3d845e1 100644
--- a/asterix-runtime/src/main/java/edu/uci/ics/asterix/runtime/evaluators/functions/StringToCodePointDescriptor.java
+++ b/asterix-runtime/src/main/java/edu/uci/ics/asterix/runtime/evaluators/functions/StringToCodePointDescriptor.java
@@ -7,7 +7,6 @@
 import edu.uci.ics.asterix.formats.nontagged.AqlSerializerDeserializerProvider;
 import edu.uci.ics.asterix.om.base.AInt32;
 import edu.uci.ics.asterix.om.base.AMutableInt32;
-import edu.uci.ics.asterix.om.base.ANull;
 import edu.uci.ics.asterix.om.functions.AsterixBuiltinFunctions;
 import edu.uci.ics.asterix.om.functions.IFunctionDescriptor;
 import edu.uci.ics.asterix.om.functions.IFunctionDescriptorFactory;
@@ -43,7 +42,6 @@
         }
     };
     private final static byte SER_STRING_TYPE_TAG = ATypeTag.STRING.serialize();
-    private final static byte SER_NULL_TYPE_TAG = ATypeTag.NULL.serialize();
 
     @Override
     public ICopyEvaluatorFactory createEvaluatorFactory(final ICopyEvaluatorFactory[] args) {
@@ -62,9 +60,6 @@
                     private ArrayBackedValueStorage inputVal = new ArrayBackedValueStorage();
 
                     @SuppressWarnings("unchecked")
-                    private ISerializerDeserializer<ANull> nullSerde = AqlSerializerDeserializerProvider.INSTANCE
-                            .getSerializerDeserializer(BuiltinType.ANULL);
-                    @SuppressWarnings("unchecked")
                     private final ISerializerDeserializer<AInt32> int32Serde = AqlSerializerDeserializerProvider.INSTANCE
                             .getSerializerDeserializer(BuiltinType.AINT32);
                     private final AMutableInt32 aInt32 = new AMutableInt32(0);
@@ -123,9 +118,7 @@
 
                                 }
                                 listBuilder.write(out, true);
-                            } else if (serString[0] == SER_NULL_TYPE_TAG)
-                                nullSerde.serialize(ANull.NULL, out);
-                            else
+                            } else
                                 throw new AlgebricksException("Expects String Type.");
                         } catch (IOException e1) {
                             throw new AlgebricksException(e1.getMessage());