Revert "Merge pull request #5091 from vespa-engine/revert-5065-bratseth/typecheck-all-2"

This reverts commit f15c8a6384031adfe0764f20e6448be4eccd517b, reversing
changes made to 2a343e5a88a023a3f3246db2f47726e229d28fac.

34 files changed, 401 insertions, 185 deletions

diff --git a/searchlib/src/main/java/com/yahoo/searchlib/rankingexpression/ExpressionFunction.java b/searchlib/src/main/java/com/yahoo/searchlib/rankingexpression/ExpressionFunction.java
index 2e2858da238..262aba89f27 100755
--- a/searchlib/src/main/java/com/yahoo/searchlib/rankingexpression/ExpressionFunction.java
+++ b/searchlib/src/main/java/com/yahoo/searchlib/rankingexpression/ExpressionFunction.java
@@ -3,6 +3,7 @@ package com.yahoo.searchlib.rankingexpression;
 
 import com.google.common.collect.ImmutableList;
 import com.yahoo.searchlib.rankingexpression.rule.ExpressionNode;
+import com.yahoo.searchlib.rankingexpression.rule.FunctionReferenceContext;
 import com.yahoo.searchlib.rankingexpression.rule.SerializationContext;
 import com.yahoo.text.Utf8;
 
@@ -11,9 +12,9 @@ import java.security.NoSuchAlgorithmException;
 import java.util.*;
 
 /**
- * <p>A function defined by a ranking expression</p>
+ * A function defined by a ranking expression
  *
- * @author <a href="mailto:simon@yahoo-inc.com">Simon Thoresen</a>
+ * @author Simon Thoresen
  * @author bratseth
  */
 public class ExpressionFunction {
@@ -23,7 +24,7 @@ public class ExpressionFunction {
     private final RankingExpression body;
 
     /**
-     * <p>Constructs a new function</p>
+     * Constructs a new function
      *
      * @param name the name of this function
      * @param arguments its argument names
@@ -43,28 +44,27 @@ public class ExpressionFunction {
     public RankingExpression getBody() { return body; }
 
     /**
-     * <p>Create and return an instance of this function based on the given
-     * arguments. If function calls are nested, this call might produce
-     * additional scripts.</p>
+     * Creates and returns an instance of this function based on the given
+     * arguments. If function calls are nested, this call may produce
+     * additional functions.
      *
      * @param context the context used to expand this
-     * @param arguments the arguments to instantiate on.
+     * @param argumentValues the arguments to instantiate on.
      * @param path the expansion path leading to this.
      * @return the script function instance created.
      */
-    public Instance expand(SerializationContext context, List<ExpressionNode> arguments, Deque<String> path) {
+    public Instance expand(SerializationContext context, List<ExpressionNode> argumentValues, Deque<String> path) {
         Map<String, String> argumentBindings = new HashMap<>();
-        for (int i = 0; i < this.arguments.size() && i < arguments.size(); ++i) {
-            argumentBindings.put(this.arguments.get(i), arguments.get(i).toString(context, path, null));
+        for (int i = 0; i < arguments.size() && i < arguments.size(); ++i) {
+            argumentBindings.put(arguments.get(i), argumentValues.get(i).toString(context, path, null));
         }
-        return new Instance(toSymbol(argumentBindings), body.getRoot().toString(context.createBinding(argumentBindings), path, null));
+        return new Instance(toSymbol(argumentBindings), body.getRoot().toString(context.withBindings(argumentBindings), path, null));
     }
 
     /**
      * Returns a symbolic string that represents this function with a given
      * list of arguments. The arguments are mangled by hashing the string
-     * representation of the argument expressions, so we might need to revisit
-     * this if we start seeing collisions.
+     * representation of the argument expressions.
      *
      * @param  argumentBindings the bound arguments to include in the symbolic name.
      * @return the symbolic name for an instance of this function
@@ -85,8 +85,8 @@ public class ExpressionFunction {
 
 
     /**
-     * <p>Returns a more unique hash code than what Java's own {@link
-     * String#hashCode()} method would produce.</p>
+     * Returns a more unique hash code than what Java's own {@link
+     * String#hashCode()} method would produce.
      *
      * @param str The string to hash.
      * @return A 64 bit long hash code.
@@ -136,4 +136,5 @@ public class ExpressionFunction {
         }
 
     }
+
 }
diff --git a/searchlib/src/main/java/com/yahoo/searchlib/rankingexpression/FeatureList.java b/searchlib/src/main/java/com/yahoo/searchlib/rankingexpression/FeatureList.java
index 49466f1974d..f0532d9d433 100755
--- a/searchlib/src/main/java/com/yahoo/searchlib/rankingexpression/FeatureList.java
+++ b/searchlib/src/main/java/com/yahoo/searchlib/rankingexpression/FeatureList.java
@@ -91,8 +91,8 @@ public class FeatureList implements Iterable<ReferenceNode> {
     /**
      * Returns the feature at the given index.
      *
-     * @param i The index of the feature to return.
-     * @return The featuer at the given index.
+     * @param i the index of the feature to return.
+     * @return the feature at the given index.
      */
     public ReferenceNode get(int i) {
         return features.get(i);
@@ -137,4 +137,5 @@ public class FeatureList implements Iterable<ReferenceNode> {
     public Iterator<ReferenceNode> iterator() {
         return features.iterator();
     }
+
 }
diff --git a/searchlib/src/main/java/com/yahoo/searchlib/rankingexpression/RankingExpression.java b/searchlib/src/main/java/com/yahoo/searchlib/rankingexpression/RankingExpression.java
index c8d90e8c4e8..6b2422d7cb2 100755
--- a/searchlib/src/main/java/com/yahoo/searchlib/rankingexpression/RankingExpression.java
+++ b/searchlib/src/main/java/com/yahoo/searchlib/rankingexpression/RankingExpression.java
@@ -244,10 +244,6 @@ public class RankingExpression implements Serializable {
      * @return a list of named rank properties required to implement this expression.
      */
     public Map<String, String> getRankProperties(List<ExpressionFunction> macros) {
-        Map<String, ExpressionFunction> arg = new HashMap<>();
-        for (ExpressionFunction function : macros) {
-            arg.put(function.getName(), function);
-        }
         Deque<String> path = new LinkedList<>();
         SerializationContext context = new SerializationContext(macros);
         String serializedRoot = root.toString(context, path, null);
@@ -272,7 +268,7 @@ public class RankingExpression implements Serializable {
      *
      * @throws IllegalArgumentException if this expression is not type correct in this context
      */
-    public TensorType type(TypeContext context) {
+    public TensorType type(TypeContext<Reference> context) {
         return root.type(context);
     }
 
diff --git a/searchlib/src/main/java/com/yahoo/searchlib/rankingexpression/Reference.java b/searchlib/src/main/java/com/yahoo/searchlib/rankingexpression/Reference.java
new file mode 100644
index 00000000000..6277721e8f5
--- /dev/null
+++ b/searchlib/src/main/java/com/yahoo/searchlib/rankingexpression/Reference.java
@@ -0,0 +1,121 @@
+// Copyright 2018 Yahoo Holdings. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
+package com.yahoo.searchlib.rankingexpression;
+
+import com.yahoo.searchlib.rankingexpression.rule.Arguments;
+import com.yahoo.searchlib.rankingexpression.rule.CompositeNode;
+import com.yahoo.searchlib.rankingexpression.rule.ExpressionNode;
+import com.yahoo.searchlib.rankingexpression.rule.ReferenceNode;
+import com.yahoo.searchlib.rankingexpression.rule.SerializationContext;
+import com.yahoo.tensor.evaluation.TypeContext;
+
+import java.util.Deque;
+import java.util.Objects;
+import java.util.Optional;
+import java.util.stream.Collectors;
+
+/**
+ * A reference to a feature, function, or value in ranking expressions
+ *
+ * @author bratseth
+ */
+public class Reference extends TypeContext.Name {
+
+    private final String name;
+    private final Arguments arguments;
+
+    /**
+     * The output, or null if none
+     */
+    private final String output;
+
+    public Reference(String name, Arguments arguments, String output) {
+        super(name);
+        Objects.requireNonNull(name, "name cannot be null");
+        Objects.requireNonNull(arguments, "arguments cannot be null");
+        this.name = name;
+        this.arguments = arguments;
+        this.output = output;
+    }
+
+    public String name() { return name; }
+
+    public Arguments arguments() { return arguments; }
+
+    public String output() { return output; }
+
+    /**
+     * Creates a reference to a simple feature consisting of a name and a single argument
+     */
+    public static Reference simple(String name, String argumentValue) {
+        return new Reference(name,
+                             new Arguments(new ReferenceNode(argumentValue)),
+                             null);
+    }
+
+    /**
+     * Returns the given simple feature as a reference, or empty if it is not a valid simple
+     * feature string on the form name(argument).
+     */
+    public static Optional<Reference> simple(String feature) {
+        int startParenthesis = feature.indexOf('(');
+        if (startParenthesis < 0)
+            return Optional.empty();
+        int endParenthesis = feature.lastIndexOf(')');
+        String featureName = feature.substring(0, startParenthesis);
+        if (startParenthesis < 1 || endParenthesis < startParenthesis) return Optional.empty();
+        String argument = feature.substring(startParenthesis + 1, endParenthesis);
+        if (argument.startsWith("'") || argument.startsWith("\""))
+            argument = argument.substring(1);
+        if (argument.endsWith("'") || argument.endsWith("\""))
+            argument = argument.substring(0, argument.length() - 1);
+        return Optional.of(simple(featureName, argument));
+    }
+
+    /**
+     * Returns whether this is a simple identifier - no arguments or output
+     */
+    public boolean isIdentifier() {
+        return this.arguments.expressions().size() == 0 && output == null;
+    }
+
+    public Reference withArguments(Arguments arguments) {
+        return new Reference(name, arguments, output);
+    }
+
+    public Reference withOutput(String output) {
+        return new Reference(name, arguments, output);
+    }
+
+    @Override
+    public boolean equals(Object o) {
+        if (o == this) return true;
+        if (!(o instanceof Reference)) return false;
+        Reference other = (Reference) o;
+        if (!Objects.equals(other.name, this.name)) return false;
+        if (!Objects.equals(other.arguments, this.arguments)) return false;
+        if (!Objects.equals(other.output, this.output)) return false;
+        return true;
+    }
+
+    @Override
+    public int hashCode() {
+        return Objects.hash(name, arguments, output);
+    }
+
+    @Override
+    public String toString() {
+        return toString(new SerializationContext(), null, null);
+    }
+
+    public String toString(SerializationContext context, Deque<String> path, CompositeNode parent) {
+        StringBuilder b = new StringBuilder(name);
+        if (arguments != null && arguments.expressions().size() > 0)
+            b.append("(").append(arguments.expressions().stream()
+                                                        .map(node -> node.toString(context, path, parent))
+                                                        .collect(Collectors.joining(","))).append(")");
+        if (output != null)
+            b.append(".").append(output);
+        return b.toString();
+    }
+
+}
diff --git a/searchlib/src/main/java/com/yahoo/searchlib/rankingexpression/evaluation/ArrayContext.java b/searchlib/src/main/java/com/yahoo/searchlib/rankingexpression/evaluation/ArrayContext.java
index 5f8daa69ecf..ee5952d9aea 100644
--- a/searchlib/src/main/java/com/yahoo/searchlib/rankingexpression/evaluation/ArrayContext.java
+++ b/searchlib/src/main/java/com/yahoo/searchlib/rankingexpression/evaluation/ArrayContext.java
@@ -2,6 +2,7 @@
 package com.yahoo.searchlib.rankingexpression.evaluation;
 
 import com.yahoo.searchlib.rankingexpression.RankingExpression;
+import com.yahoo.searchlib.rankingexpression.Reference;
 import com.yahoo.tensor.TensorType;
 
 import java.util.Arrays;
@@ -82,8 +83,8 @@ public class ArrayContext extends AbstractArrayContext implements Cloneable {
     }
 
     @Override
-    public TensorType getType(String name) {
-        Integer index = nameToIndex().get(name);
+    public TensorType getType(Reference reference) {
+        Integer index = nameToIndex().get(reference.toString());
         if (index == null) return null;
         return values[index].type();
     }
diff --git a/searchlib/src/main/java/com/yahoo/searchlib/rankingexpression/evaluation/Context.java b/searchlib/src/main/java/com/yahoo/searchlib/rankingexpression/evaluation/Context.java
index 861f9565d66..4e046df11ca 100644
--- a/searchlib/src/main/java/com/yahoo/searchlib/rankingexpression/evaluation/Context.java
+++ b/searchlib/src/main/java/com/yahoo/searchlib/rankingexpression/evaluation/Context.java
@@ -1,9 +1,11 @@
 // Copyright 2017 Yahoo Holdings. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
 package com.yahoo.searchlib.rankingexpression.evaluation;
 
+import com.yahoo.searchlib.rankingexpression.Reference;
 import com.yahoo.searchlib.rankingexpression.rule.Arguments;
 import com.yahoo.searchlib.rankingexpression.rule.ExpressionNode;
 import com.yahoo.tensor.Tensor;
+import com.yahoo.tensor.TensorType;
 import com.yahoo.tensor.evaluation.EvaluationContext;
 
 import java.util.Set;
@@ -14,7 +16,7 @@ import java.util.stream.Collectors;
  *
  * @author bratseth
  */
-public abstract class Context implements EvaluationContext {
+public abstract class Context implements EvaluationContext<Reference> {
 
     /**
      * Returns the value of a simple variable name.
@@ -24,6 +26,11 @@ public abstract class Context implements EvaluationContext {
      */
     public abstract Value get(String name);
 
+    @Override
+    public TensorType getType(String reference) {
+        throw new UnsupportedOperationException("Not able to parse gereral references from string form");
+    }
+
     /** Returns a variable as a tensor */
     @Override
     public Tensor getTensor(String name) { return get(name).asTensor(); }
@@ -46,6 +53,7 @@ public abstract class Context implements EvaluationContext {
      *                  calculation to output several), or null to output the
      *                  "main" (or only) value.
      */
+    // TODO: Remove/change to use reference?
     public Value get(String name, Arguments arguments, String output) {
         if (arguments != null && arguments.expressions().size() > 0)
             name = name + "(" + arguments.expressions().stream().map(ExpressionNode::toString).collect(Collectors.joining(",")) + ")";
diff --git a/searchlib/src/main/java/com/yahoo/searchlib/rankingexpression/evaluation/DoubleOnlyArrayContext.java b/searchlib/src/main/java/com/yahoo/searchlib/rankingexpression/evaluation/DoubleOnlyArrayContext.java
index 0625e8506cc..0004036da4b 100644
--- a/searchlib/src/main/java/com/yahoo/searchlib/rankingexpression/evaluation/DoubleOnlyArrayContext.java
+++ b/searchlib/src/main/java/com/yahoo/searchlib/rankingexpression/evaluation/DoubleOnlyArrayContext.java
@@ -2,6 +2,7 @@
 package com.yahoo.searchlib.rankingexpression.evaluation;
 
 import com.yahoo.searchlib.rankingexpression.RankingExpression;
+import com.yahoo.searchlib.rankingexpression.Reference;
 import com.yahoo.tensor.TensorType;
 
 /**
@@ -68,7 +69,9 @@ public class DoubleOnlyArrayContext extends AbstractArrayContext {
     }
 
     @Override
-    public TensorType getType(String name) { return TensorType.empty; }
+    public TensorType getType(Reference reference) {
+        return TensorType.empty; // Double only
+    }
 
     /** Perform a slow lookup by name */
     @Override
diff --git a/searchlib/src/main/java/com/yahoo/searchlib/rankingexpression/evaluation/MapContext.java b/searchlib/src/main/java/com/yahoo/searchlib/rankingexpression/evaluation/MapContext.java
index a81d0c89f8f..4ef24d60bba 100644
--- a/searchlib/src/main/java/com/yahoo/searchlib/rankingexpression/evaluation/MapContext.java
+++ b/searchlib/src/main/java/com/yahoo/searchlib/rankingexpression/evaluation/MapContext.java
@@ -1,6 +1,7 @@
 // Copyright 2017 Yahoo Holdings. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
 package com.yahoo.searchlib.rankingexpression.evaluation;
 
+import com.yahoo.searchlib.rankingexpression.Reference;
 import com.yahoo.tensor.TensorType;
 
 import java.util.Collections;
@@ -15,7 +16,7 @@ import java.util.Set;
  */
 public class MapContext extends Context {
 
-    private Map<String, Value> bindings = new HashMap<>();
+    private Map<String, Value> bindings = new HashMap<>(); // TODO: Change String to Reference
 
     private boolean frozen = false;
 
@@ -42,8 +43,8 @@ public class MapContext extends Context {
 
     /** Returns the type of the given value key, or null if it is not bound. */
     @Override
-    public TensorType getType(String key) {
-        Value value = bindings.get(key);
+    public TensorType getType(Reference key) {
+        Value value = bindings.get(key.toString());
         if (value == null) return null;
         return value.type();
     }
diff --git a/searchlib/src/main/java/com/yahoo/searchlib/rankingexpression/evaluation/MapTypeContext.java b/searchlib/src/main/java/com/yahoo/searchlib/rankingexpression/evaluation/MapTypeContext.java
new file mode 100644
index 00000000000..2a42e2d92f7
--- /dev/null
+++ b/searchlib/src/main/java/com/yahoo/searchlib/rankingexpression/evaluation/MapTypeContext.java
@@ -0,0 +1,38 @@
+// Copyright 2018 Yahoo Holdings. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
+package com.yahoo.searchlib.rankingexpression.evaluation;// Copyright 2018 Yahoo Holdings. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
+
+import com.yahoo.searchlib.rankingexpression.Reference;
+import com.yahoo.tensor.TensorType;
+import com.yahoo.tensor.evaluation.TypeContext;
+
+import java.util.Collections;
+import java.util.HashMap;
+import java.util.Map;
+
+/**
+ * A context which only contains type information.
+ *
+ * @author bratseth
+ */
+public class MapTypeContext implements TypeContext<Reference> {
+
+    private final Map<Reference, TensorType> featureTypes = new HashMap<>();
+
+    public void setType(Reference reference, TensorType type) {
+        featureTypes.put(reference, type);
+    }
+
+    @Override
+    public TensorType getType(String reference) {
+        throw new UnsupportedOperationException("Not able to parse gereral references from string form");
+    }
+
+    @Override
+    public TensorType getType(Reference reference) {
+        return featureTypes.get(reference);
+    }
+
+    /** Returns an unmodifiable map of the bindings in this */
+    public Map<Reference, TensorType> bindings() { return Collections.unmodifiableMap(featureTypes); }
+
+}
diff --git a/searchlib/src/main/java/com/yahoo/searchlib/rankingexpression/evaluation/TypeMapContext.java b/searchlib/src/main/java/com/yahoo/searchlib/rankingexpression/evaluation/TypeMapContext.java
deleted file mode 100644
index ff2088263d8..00000000000
--- a/searchlib/src/main/java/com/yahoo/searchlib/rankingexpression/evaluation/TypeMapContext.java
+++ /dev/null
@@ -1,32 +0,0 @@
-// Copyright 2018 Yahoo Holdings. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
-package com.yahoo.searchlib.rankingexpression.evaluation;// Copyright 2018 Yahoo Holdings. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
-
-import com.yahoo.tensor.TensorType;
-import com.yahoo.tensor.evaluation.TypeContext;
-
-import java.util.Collections;
-import java.util.HashMap;
-import java.util.Map;
-
-/**
- * A context which only contains type information.
- *
- * @author bratseth
- */
-public class TypeMapContext implements TypeContext {
-
-    private final Map<String, TensorType> featureTypes = new HashMap<>();
-
-    public void setType(String name, TensorType type) {
-        featureTypes.put(name, type);
-    }
-
-    @Override
-    public TensorType getType(String name) {
-        return featureTypes.get(name);
-    }
-
-    /** Returns an unmodifiable map of the bindings in this */
-    public Map<String, TensorType> bindings() { return Collections.unmodifiableMap(featureTypes); }
-
-}
diff --git a/searchlib/src/main/java/com/yahoo/searchlib/rankingexpression/evaluation/gbdtoptimization/GBDTForestNode.java b/searchlib/src/main/java/com/yahoo/searchlib/rankingexpression/evaluation/gbdtoptimization/GBDTForestNode.java
index 8ee4cdbf297..649c70122f1 100644
--- a/searchlib/src/main/java/com/yahoo/searchlib/rankingexpression/evaluation/gbdtoptimization/GBDTForestNode.java
+++ b/searchlib/src/main/java/com/yahoo/searchlib/rankingexpression/evaluation/gbdtoptimization/GBDTForestNode.java
@@ -1,6 +1,7 @@
 // Copyright 2017 Yahoo Holdings. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
 package com.yahoo.searchlib.rankingexpression.evaluation.gbdtoptimization;
 
+import com.yahoo.searchlib.rankingexpression.Reference;
 import com.yahoo.searchlib.rankingexpression.evaluation.Context;
 import com.yahoo.searchlib.rankingexpression.evaluation.DoubleValue;
 import com.yahoo.searchlib.rankingexpression.evaluation.Value;
@@ -26,7 +27,7 @@ public class GBDTForestNode extends ExpressionNode {
     }
 
     @Override
-    public final TensorType type(TypeContext context) { return TensorType.empty; }
+    public final TensorType type(TypeContext<Reference> context) { return TensorType.empty; }
 
     @Override
     public final Value evaluate(Context context) {
diff --git a/searchlib/src/main/java/com/yahoo/searchlib/rankingexpression/evaluation/gbdtoptimization/GBDTNode.java b/searchlib/src/main/java/com/yahoo/searchlib/rankingexpression/evaluation/gbdtoptimization/GBDTNode.java
index aac635b2545..53a286f09f6 100644
--- a/searchlib/src/main/java/com/yahoo/searchlib/rankingexpression/evaluation/gbdtoptimization/GBDTNode.java
+++ b/searchlib/src/main/java/com/yahoo/searchlib/rankingexpression/evaluation/gbdtoptimization/GBDTNode.java
@@ -1,6 +1,7 @@
 // Copyright 2017 Yahoo Holdings. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
 package com.yahoo.searchlib.rankingexpression.evaluation.gbdtoptimization;
 
+import com.yahoo.searchlib.rankingexpression.Reference;
 import com.yahoo.searchlib.rankingexpression.evaluation.Context;
 import com.yahoo.searchlib.rankingexpression.evaluation.DoubleValue;
 import com.yahoo.searchlib.rankingexpression.evaluation.Value;
@@ -51,7 +52,7 @@ public final class GBDTNode extends ExpressionNode {
     public final double[] values() { return values; }
 
     @Override
-    public final TensorType type(TypeContext context) { return TensorType.empty; }
+    public final TensorType type(TypeContext<Reference> context) { return TensorType.empty; }
 
     @Override
     public final Value evaluate(Context context) {
diff --git a/searchlib/src/main/java/com/yahoo/searchlib/rankingexpression/rule/Arguments.java b/searchlib/src/main/java/com/yahoo/searchlib/rankingexpression/rule/Arguments.java
index fb9a7cb9ad7..d3a12d0f312 100644
--- a/searchlib/src/main/java/com/yahoo/searchlib/rankingexpression/rule/Arguments.java
+++ b/searchlib/src/main/java/com/yahoo/searchlib/rankingexpression/rule/Arguments.java
@@ -13,7 +13,7 @@ import java.util.List;
 
 /**
  * A set of argument expressions to a function or feature.
- * This is immutable.
+ * This is a value object.
  *
  * @author bratseth
  */
@@ -22,7 +22,11 @@ public final class Arguments implements Serializable {
     private final ImmutableList<ExpressionNode> expressions;
 
     public Arguments() {
-        this(null);
+        this(ImmutableList.of());
+    }
+
+    public Arguments(ExpressionNode singleArgument) {
+        this(ImmutableList.of(singleArgument));
     }
 
     public Arguments(List<? extends ExpressionNode> expressions) {
@@ -38,9 +42,12 @@ public final class Arguments implements Serializable {
         this.expressions = b.build();
     }
 
-    /** Returns an unmodifiable list of the expressions in this */
+    /** Returns an unmodifiable list of the expressions in this, never null */
     public List<ExpressionNode> expressions() { return expressions; }
 
+    /** Returns the number of arguments in this */
+    public int size() { return expressions.size(); }
+
     /** Evaluate all arguments in this */
     public Value[] evaluate(Context context) {
         Value[] values=new Value[expressions.size()];
@@ -62,8 +69,9 @@ public final class Arguments implements Serializable {
     }
 
     @Override
-    public boolean equals(Object rhs) {
-        return rhs instanceof Arguments && expressions.equals(((Arguments)rhs).expressions);
+    public boolean equals(Object other) {
+        if (other == this) return true;
+        return other instanceof Arguments && expressions.equals(((Arguments)other).expressions);
     }
 
     @Override
diff --git a/searchlib/src/main/java/com/yahoo/searchlib/rankingexpression/rule/ArithmeticNode.java b/searchlib/src/main/java/com/yahoo/searchlib/rankingexpression/rule/ArithmeticNode.java
index fc6428a4c33..49c49bed9bd 100755
--- a/searchlib/src/main/java/com/yahoo/searchlib/rankingexpression/rule/ArithmeticNode.java
+++ b/searchlib/src/main/java/com/yahoo/searchlib/rankingexpression/rule/ArithmeticNode.java
@@ -2,6 +2,7 @@
 package com.yahoo.searchlib.rankingexpression.rule;
 
 import com.google.common.collect.ImmutableList;
+import com.yahoo.searchlib.rankingexpression.Reference;
 import com.yahoo.searchlib.rankingexpression.evaluation.Context;
 import com.yahoo.searchlib.rankingexpression.evaluation.Value;
 import com.yahoo.tensor.TensorType;
@@ -80,7 +81,7 @@ public final class ArithmeticNode extends CompositeNode {
     }
 
     @Override
-    public TensorType type(TypeContext context) {
+    public TensorType type(TypeContext<Reference> context) {
         // Compute type using tensor types as arithmetic operators are supported on tensors
         // and is correct also in the special case of doubles.
         // As all our functions are type-commutative, we don't need to take operator precedence into account
diff --git a/searchlib/src/main/java/com/yahoo/searchlib/rankingexpression/rule/BooleanNode.java b/searchlib/src/main/java/com/yahoo/searchlib/rankingexpression/rule/BooleanNode.java
index 1d7d9b1ecda..cd4ddbcae55 100755
--- a/searchlib/src/main/java/com/yahoo/searchlib/rankingexpression/rule/BooleanNode.java
+++ b/searchlib/src/main/java/com/yahoo/searchlib/rankingexpression/rule/BooleanNode.java
@@ -5,7 +5,6 @@ package com.yahoo.searchlib.rankingexpression.rule;
  * A node which produces a boolean value when evaluated.
  *
  * @author bratseth
- * @since  5.1.21
  */
 public abstract class BooleanNode extends CompositeNode {
 }
diff --git a/searchlib/src/main/java/com/yahoo/searchlib/rankingexpression/rule/ComparisonNode.java b/searchlib/src/main/java/com/yahoo/searchlib/rankingexpression/rule/ComparisonNode.java
index 7601c0e6180..eb328486045 100644
--- a/searchlib/src/main/java/com/yahoo/searchlib/rankingexpression/rule/ComparisonNode.java
+++ b/searchlib/src/main/java/com/yahoo/searchlib/rankingexpression/rule/ComparisonNode.java
@@ -1,6 +1,7 @@
 // Copyright 2017 Yahoo Holdings. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
 package com.yahoo.searchlib.rankingexpression.rule;
 
+import com.yahoo.searchlib.rankingexpression.Reference;
 import com.yahoo.searchlib.rankingexpression.evaluation.Context;
 import com.yahoo.searchlib.rankingexpression.evaluation.Value;
 import com.yahoo.tensor.TensorType;
@@ -49,7 +50,7 @@ public class ComparisonNode extends BooleanNode {
     }
 
     @Override
-    public TensorType type(TypeContext context) {
+    public TensorType type(TypeContext<Reference> context) {
         return TensorType.empty; // by definition
     }
 
diff --git a/searchlib/src/main/java/com/yahoo/searchlib/rankingexpression/rule/ConstantNode.java b/searchlib/src/main/java/com/yahoo/searchlib/rankingexpression/rule/ConstantNode.java
index 1ea8d03f0eb..3ddd7223349 100755
--- a/searchlib/src/main/java/com/yahoo/searchlib/rankingexpression/rule/ConstantNode.java
+++ b/searchlib/src/main/java/com/yahoo/searchlib/rankingexpression/rule/ConstantNode.java
@@ -1,6 +1,7 @@
 // Copyright 2017 Yahoo Holdings. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
 package com.yahoo.searchlib.rankingexpression.rule;
 
+import com.yahoo.searchlib.rankingexpression.Reference;
 import com.yahoo.searchlib.rankingexpression.evaluation.Context;
 import com.yahoo.searchlib.rankingexpression.evaluation.Value;
 import com.yahoo.tensor.TensorType;
@@ -49,7 +50,7 @@ public final class ConstantNode extends ExpressionNode {
     }
 
     @Override
-    public TensorType type(TypeContext context) { return value.type(); }
+    public TensorType type(TypeContext<Reference> context) { return value.type(); }
 
     @Override
     public Value evaluate(Context context) {
diff --git a/searchlib/src/main/java/com/yahoo/searchlib/rankingexpression/rule/EmbracedNode.java b/searchlib/src/main/java/com/yahoo/searchlib/rankingexpression/rule/EmbracedNode.java
index fd9fab99db8..47c2897e4a4 100755
--- a/searchlib/src/main/java/com/yahoo/searchlib/rankingexpression/rule/EmbracedNode.java
+++ b/searchlib/src/main/java/com/yahoo/searchlib/rankingexpression/rule/EmbracedNode.java
@@ -1,6 +1,7 @@
 // Copyright 2017 Yahoo Holdings. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
 package com.yahoo.searchlib.rankingexpression.rule;
 
+import com.yahoo.searchlib.rankingexpression.Reference;
 import com.yahoo.searchlib.rankingexpression.evaluation.Context;
 import com.yahoo.searchlib.rankingexpression.evaluation.Value;
 import com.yahoo.tensor.TensorType;
@@ -50,7 +51,7 @@ public final class EmbracedNode extends CompositeNode {
     }
 
     @Override
-    public TensorType type(TypeContext context) {
+    public TensorType type(TypeContext<Reference> context) {
         return value.type(context);
     }
 
diff --git a/searchlib/src/main/java/com/yahoo/searchlib/rankingexpression/rule/ExpressionNode.java b/searchlib/src/main/java/com/yahoo/searchlib/rankingexpression/rule/ExpressionNode.java
index 477f4db4981..6bb163590de 100755
--- a/searchlib/src/main/java/com/yahoo/searchlib/rankingexpression/rule/ExpressionNode.java
+++ b/searchlib/src/main/java/com/yahoo/searchlib/rankingexpression/rule/ExpressionNode.java
@@ -1,6 +1,7 @@
 // Copyright 2017 Yahoo Holdings. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
 package com.yahoo.searchlib.rankingexpression.rule;
 
+import com.yahoo.searchlib.rankingexpression.Reference;
 import com.yahoo.searchlib.rankingexpression.evaluation.Context;
 import com.yahoo.searchlib.rankingexpression.evaluation.Value;
 import com.yahoo.tensor.TensorType;
@@ -48,7 +49,7 @@ public abstract class ExpressionNode implements Serializable {
      * @param context the variable type bindings to use for this evaluation
      * @throws IllegalArgumentException if there are variables which are not bound in the given map
      */
-    public abstract TensorType type(TypeContext context);
+    public abstract TensorType type(TypeContext<Reference> context);
 
     /**
      * Returns the value of evaluating this expression over the given context.
diff --git a/searchlib/src/main/java/com/yahoo/searchlib/rankingexpression/rule/FunctionNode.java b/searchlib/src/main/java/com/yahoo/searchlib/rankingexpression/rule/FunctionNode.java
index 79515229019..1da2210a39c 100755
--- a/searchlib/src/main/java/com/yahoo/searchlib/rankingexpression/rule/FunctionNode.java
+++ b/searchlib/src/main/java/com/yahoo/searchlib/rankingexpression/rule/FunctionNode.java
@@ -1,6 +1,7 @@
 // Copyright 2017 Yahoo Holdings. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
 package com.yahoo.searchlib.rankingexpression.rule;
 
+import com.yahoo.searchlib.rankingexpression.Reference;
 import com.yahoo.searchlib.rankingexpression.evaluation.Context;
 import com.yahoo.searchlib.rankingexpression.evaluation.DoubleValue;
 import com.yahoo.searchlib.rankingexpression.evaluation.Value;
@@ -67,7 +68,7 @@ public final class FunctionNode extends CompositeNode {
     }
 
     @Override
-    public TensorType type(TypeContext context) {
+    public TensorType type(TypeContext<Reference> context) {
         if (arguments.expressions().size() == 0)
             return TensorType.empty;
 
diff --git a/searchlib/src/main/java/com/yahoo/searchlib/rankingexpression/rule/FunctionReferenceContext.java b/searchlib/src/main/java/com/yahoo/searchlib/rankingexpression/rule/FunctionReferenceContext.java
new file mode 100644
index 00000000000..ed1e2838717
--- /dev/null
+++ b/searchlib/src/main/java/com/yahoo/searchlib/rankingexpression/rule/FunctionReferenceContext.java
@@ -0,0 +1,74 @@
+// Copyright 2018 Yahoo Holdings. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
+package com.yahoo.searchlib.rankingexpression.rule;
+
+import com.google.common.collect.ImmutableMap;
+import com.yahoo.searchlib.rankingexpression.ExpressionFunction;
+
+import java.util.Collection;
+import java.util.Collections;
+import java.util.HashMap;
+import java.util.Map;
+
+/**
+ * The context of a function invocation.
+ *
+ * @author bratseth
+ */
+public class FunctionReferenceContext {
+
+    /** Expression functions indexed by name */
+    private final ImmutableMap<String, ExpressionFunction> functions;
+
+    /** Mapping from argument names to the expressions they resolve to */
+    // TODO: Make private
+    public final Map<String, String> bindings = new HashMap<>();
+
+    /** Create a context for a single serialization task */
+    public FunctionReferenceContext() {
+        this(Collections.emptyList());
+    }
+
+    /** Create a context for a single serialization task */
+    public FunctionReferenceContext(Collection<ExpressionFunction> functions) {
+        this(toMap(functions), Collections.emptyMap());
+    }
+
+    public FunctionReferenceContext(Collection<ExpressionFunction> functions, Map<String, String> bindings) {
+        this(toMap(functions), bindings);
+    }
+
+    /** Create a context for a single serialization task */
+    public FunctionReferenceContext(Map<String, ExpressionFunction> functions) {
+        this(functions.values());
+    }
+
+    /** Create a context for a single serialization task */
+    public FunctionReferenceContext(Map<String, ExpressionFunction> functions, Map<String, String> bindings) {
+        this.functions = ImmutableMap.copyOf(functions);
+        if (bindings != null)
+            this.bindings.putAll(bindings);
+    }
+
+    private static ImmutableMap<String, ExpressionFunction> toMap(Collection<ExpressionFunction> list) {
+        ImmutableMap.Builder<String,ExpressionFunction> mapBuilder = new ImmutableMap.Builder<>();
+        for (ExpressionFunction function : list)
+            mapBuilder.put(function.getName(), function);
+        return mapBuilder.build();
+    }
+
+    /**
+     * Returns a function or null if it isn't defined in this context
+     */
+    public ExpressionFunction getFunction(String name) { return functions.get(name); }
+
+    protected Map<String, ExpressionFunction> functions() { return functions; }
+
+    /** Returns the resolution of an argument, or null if it isn't defined in this context */
+    public String getBinding(String name) { return bindings.get(name); }
+
+    /** Returns a new context with the bindings replaced by the given bindings */
+    public FunctionReferenceContext withBindings(Map<String, String> bindings) {
+        return new FunctionReferenceContext(this.functions, bindings);
+    }
+
+}
diff --git a/searchlib/src/main/java/com/yahoo/searchlib/rankingexpression/rule/GeneratorLambdaFunctionNode.java b/searchlib/src/main/java/com/yahoo/searchlib/rankingexpression/rule/GeneratorLambdaFunctionNode.java
index e42884ecc05..c87eb0ace39 100644
--- a/searchlib/src/main/java/com/yahoo/searchlib/rankingexpression/rule/GeneratorLambdaFunctionNode.java
+++ b/searchlib/src/main/java/com/yahoo/searchlib/rankingexpression/rule/GeneratorLambdaFunctionNode.java
@@ -1,6 +1,7 @@
 // Copyright 2017 Yahoo Holdings. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
 package com.yahoo.searchlib.rankingexpression.rule;
 
+import com.yahoo.searchlib.rankingexpression.Reference;
 import com.yahoo.searchlib.rankingexpression.evaluation.Context;
 import com.yahoo.searchlib.rankingexpression.evaluation.MapContext;
 import com.yahoo.searchlib.rankingexpression.evaluation.Value;
@@ -48,7 +49,7 @@ public class GeneratorLambdaFunctionNode extends CompositeNode {
     }
 
     @Override
-    public TensorType type(TypeContext context) { return type; }
+    public TensorType type(TypeContext<Reference> context) { return type; }
 
     /** Evaluate this in a context which must have the arguments bound */
     @Override
diff --git a/searchlib/src/main/java/com/yahoo/searchlib/rankingexpression/rule/IfNode.java b/searchlib/src/main/java/com/yahoo/searchlib/rankingexpression/rule/IfNode.java
index 66b250736e8..ee4edac4941 100755
--- a/searchlib/src/main/java/com/yahoo/searchlib/rankingexpression/rule/IfNode.java
+++ b/searchlib/src/main/java/com/yahoo/searchlib/rankingexpression/rule/IfNode.java
@@ -1,6 +1,7 @@
 // Copyright 2017 Yahoo Holdings. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
 package com.yahoo.searchlib.rankingexpression.rule;
 
+import com.yahoo.searchlib.rankingexpression.Reference;
 import com.yahoo.searchlib.rankingexpression.evaluation.Context;
 import com.yahoo.searchlib.rankingexpression.evaluation.Value;
 import com.yahoo.tensor.TensorType;
@@ -75,7 +76,7 @@ public final class IfNode extends CompositeNode {
     }
 
     @Override
-    public TensorType type(TypeContext context) {
+    public TensorType type(TypeContext<Reference> context) {
         TensorType trueType = trueExpression.type(context);
         TensorType falseType = falseExpression.type(context);
         return trueType.dimensionwiseGeneralizationWith(falseType).orElseThrow(() ->
diff --git a/searchlib/src/main/java/com/yahoo/searchlib/rankingexpression/rule/LambdaFunctionNode.java b/searchlib/src/main/java/com/yahoo/searchlib/rankingexpression/rule/LambdaFunctionNode.java
index da946228291..61086f8182a 100644
--- a/searchlib/src/main/java/com/yahoo/searchlib/rankingexpression/rule/LambdaFunctionNode.java
+++ b/searchlib/src/main/java/com/yahoo/searchlib/rankingexpression/rule/LambdaFunctionNode.java
@@ -2,6 +2,7 @@
 package com.yahoo.searchlib.rankingexpression.rule;
 
 import com.google.common.collect.ImmutableList;
+import com.yahoo.searchlib.rankingexpression.Reference;
 import com.yahoo.searchlib.rankingexpression.evaluation.Context;
 import com.yahoo.searchlib.rankingexpression.evaluation.MapContext;
 import com.yahoo.searchlib.rankingexpression.evaluation.Value;
@@ -57,7 +58,7 @@ public class LambdaFunctionNode extends CompositeNode {
     }
 
     @Override
-    public TensorType type(TypeContext context) {
+    public TensorType type(TypeContext<Reference> context) {
         return TensorType.empty; // by definition - no nested lambdas
     }
 
diff --git a/searchlib/src/main/java/com/yahoo/searchlib/rankingexpression/rule/NameNode.java b/searchlib/src/main/java/com/yahoo/searchlib/rankingexpression/rule/NameNode.java
index f55ed59b65c..f1adf331630 100755
--- a/searchlib/src/main/java/com/yahoo/searchlib/rankingexpression/rule/NameNode.java
+++ b/searchlib/src/main/java/com/yahoo/searchlib/rankingexpression/rule/NameNode.java
@@ -1,6 +1,7 @@
 // Copyright 2017 Yahoo Holdings. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
 package com.yahoo.searchlib.rankingexpression.rule;
 
+import com.yahoo.searchlib.rankingexpression.Reference;
 import com.yahoo.searchlib.rankingexpression.evaluation.Context;
 import com.yahoo.searchlib.rankingexpression.evaluation.Value;
 import com.yahoo.tensor.TensorType;
@@ -14,6 +15,7 @@ import java.util.Deque;
  *
  * @author Simon Thoresen
  */
+// TODO: This is achieved by ReferenceNode in almost all cases - remove this
 public final class NameNode extends ExpressionNode {
 
     private final String name;
@@ -32,7 +34,7 @@ public final class NameNode extends ExpressionNode {
     }
 
     @Override
-    public TensorType type(TypeContext context) { throw new RuntimeException("Named nodes can not have a type"); }
+    public TensorType type(TypeContext<Reference> context) { throw new RuntimeException("Named nodes can not have a type"); }
 
     @Override
     public Value evaluate(Context context) {
diff --git a/searchlib/src/main/java/com/yahoo/searchlib/rankingexpression/rule/NegativeNode.java b/searchlib/src/main/java/com/yahoo/searchlib/rankingexpression/rule/NegativeNode.java
index 9cbe5f98c72..fcc03dc4862 100644
--- a/searchlib/src/main/java/com/yahoo/searchlib/rankingexpression/rule/NegativeNode.java
+++ b/searchlib/src/main/java/com/yahoo/searchlib/rankingexpression/rule/NegativeNode.java
@@ -1,6 +1,7 @@
 // Copyright 2017 Yahoo Holdings. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
 package com.yahoo.searchlib.rankingexpression.rule;
 
+import com.yahoo.searchlib.rankingexpression.Reference;
 import com.yahoo.searchlib.rankingexpression.evaluation.Context;
 import com.yahoo.searchlib.rankingexpression.evaluation.Value;
 import com.yahoo.tensor.TensorType;
@@ -38,7 +39,7 @@ public class NegativeNode extends CompositeNode {
     }
 
     @Override
-    public TensorType type(TypeContext context) {
+    public TensorType type(TypeContext<Reference> context) {
         return value.type(context);
     }
 
diff --git a/searchlib/src/main/java/com/yahoo/searchlib/rankingexpression/rule/NotNode.java b/searchlib/src/main/java/com/yahoo/searchlib/rankingexpression/rule/NotNode.java
index e7041600635..a539f496ff5 100644
--- a/searchlib/src/main/java/com/yahoo/searchlib/rankingexpression/rule/NotNode.java
+++ b/searchlib/src/main/java/com/yahoo/searchlib/rankingexpression/rule/NotNode.java
@@ -1,6 +1,7 @@
 // Copyright 2017 Yahoo Holdings. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
 package com.yahoo.searchlib.rankingexpression.rule;
 
+import com.yahoo.searchlib.rankingexpression.Reference;
 import com.yahoo.searchlib.rankingexpression.evaluation.Context;
 import com.yahoo.searchlib.rankingexpression.evaluation.Value;
 import com.yahoo.tensor.TensorType;
@@ -38,7 +39,7 @@ public class NotNode extends BooleanNode {
     }
 
     @Override
-    public TensorType type(TypeContext context) {
+    public TensorType type(TypeContext<Reference> context) {
         return value.type(context);
     }
 
diff --git a/searchlib/src/main/java/com/yahoo/searchlib/rankingexpression/rule/ReferenceNode.java b/searchlib/src/main/java/com/yahoo/searchlib/rankingexpression/rule/ReferenceNode.java
index 05a6773c5cb..78f53b1593d 100755
--- a/searchlib/src/main/java/com/yahoo/searchlib/rankingexpression/rule/ReferenceNode.java
+++ b/searchlib/src/main/java/com/yahoo/searchlib/rankingexpression/rule/ReferenceNode.java
@@ -3,6 +3,7 @@ package com.yahoo.searchlib.rankingexpression.rule;
 
 import com.yahoo.searchlib.rankingexpression.ExpressionFunction;
 import com.yahoo.searchlib.rankingexpression.RankingExpression;
+import com.yahoo.searchlib.rankingexpression.Reference;
 import com.yahoo.searchlib.rankingexpression.evaluation.Context;
 import com.yahoo.searchlib.rankingexpression.evaluation.Value;
 import com.yahoo.tensor.TensorType;
@@ -13,114 +14,102 @@ import java.util.Deque;
 import java.util.List;
 
 /**
- * A node referring either to a value in the context or to another named ranking expression.
+ * A node referring either to a value in the context or to a named ranking expression (function aka macro).
  *
  * @author simon
  * @author bratseth
  */
 public final class ReferenceNode extends CompositeNode {
 
-    private final String name, output;
-
-    private final Arguments arguments;
+    private final Reference reference;
 
+    /* Creates a node with a simple identifier reference */
     public ReferenceNode(String name) {
         this(name, null, null);
     }
 
     public ReferenceNode(String name, List<? extends ExpressionNode> arguments, String output) {
-        this.name = name;
-        this.arguments = arguments != null ? new Arguments(arguments) : new Arguments();
-        this.output = output;
+        this.reference = new Reference(name,
+                                       arguments != null ? new Arguments(arguments) : new Arguments(),
+                                       output);
+    }
+
+    public ReferenceNode(Reference reference) {
+        this.reference = reference;
     }
 
     public String getName() {
-        return name;
+        return reference.name();
     }
 
     /** Returns the arguments, never null */
-    public Arguments getArguments() { return arguments; }
+    public Arguments getArguments() { return reference.arguments(); }
 
     /** Returns a copy of this where the arguments are replaced by the given arguments */
     public ReferenceNode setArguments(List<ExpressionNode> arguments) {
-        return new ReferenceNode(name, arguments, output);
+        return new ReferenceNode(reference.withArguments(new Arguments(arguments)));
     }
 
     /** Returns the specific output this references, or null if none specified */
-    public String getOutput() { return output; }
+    public String getOutput() { return reference.output(); }
 
     /** Returns a copy of this node with a modified output */
     public ReferenceNode setOutput(String output) {
-        return new ReferenceNode(name, arguments.expressions(), output);
+        return new ReferenceNode(reference.withOutput(output));
     }
 
     /** Returns an empty list as this has no children */
     @Override
-    public List<ExpressionNode> children() { return arguments.expressions(); }
+    public List<ExpressionNode> children() { return reference.arguments().expressions(); }
 
     @Override
     public String toString(SerializationContext context, Deque<String> path, CompositeNode parent) {
-        if (path == null)
-            path = new ArrayDeque<>();
-        String myName = this.name;
-        String myOutput = this.output;
-        List<ExpressionNode> myArguments = this.arguments.expressions();
-
-        String resolvedArgument = context.getBinding(myName);
-        if (resolvedArgument != null && this.arguments.expressions().size() == 0 && myOutput == null) {
-            // Replace this whole node with the value of the argument value that it maps to
-            myName = resolvedArgument;
-            myArguments = null;
-            myOutput = null;
-        } else if (context.getFunction(myName) != null) {
-            // Replace by the referenced expression
-            ExpressionFunction function = context.getFunction(myName);
-            if (function != null && myArguments != null && function.arguments().size() == myArguments.size() && myOutput == null) {
-                String myPath = name + this.arguments.expressions();
-                if (path.contains(myPath)) {
-                    throw new IllegalStateException("Cycle in ranking expression function: " + path);
-                }
-                path.addLast(myPath);
-                ExpressionFunction.Instance instance = function.expand(context, myArguments, path);
-                path.removeLast();
-                context.addFunctionSerialization(RankingExpression.propertyName(instance.getName()), instance.getExpressionString());
-                myName = "rankingExpression(" + instance.getName() + ")";
-                myArguments = null;
-                myOutput = null;
-            }
+        if (reference.isIdentifier() && context.getBinding(getName()) != null) {
+            // a bound identifier: replace by the value it is bound to
+            return context.getBinding(getName());
         }
-        // Always print the same way, the magic is already done.
-        StringBuilder ret = new StringBuilder(myName);
-        if (myArguments != null && myArguments.size() > 0) {
-            ret.append("(");
-            for (int i = 0; i < myArguments.size(); ++i) {
-                ret.append(myArguments.get(i).toString(context, path, this));
-                if (i < myArguments.size() - 1) {
-                    ret.append(",");
-                }
-            }
-            ret.append(")");
+
+        ExpressionFunction function = context.getFunction(getName());
+        if (function != null && function.arguments().size() == getArguments().size() && getOutput() == null) {
+            // a function reference: replace by the referenced function wrapped in rankingExpression
+            if (path == null)
+                path = new ArrayDeque<>();
+            String myPath = getName() + getArguments().expressions();
+            if (path.contains(myPath))
+                throw new IllegalStateException("Cycle in ranking expression function: " + path);
+            path.addLast(myPath);
+            ExpressionFunction.Instance instance = function.expand(context, getArguments().expressions(), path);
+            path.removeLast();
+            context.addFunctionSerialization(RankingExpression.propertyName(instance.getName()), instance.getExpressionString());
+            return "rankingExpression(" + instance.getName() + ")";
         }
-        ret.append(myOutput != null ? "." + myOutput : "");
-        return ret.toString();
+
+        // not resolved in this context: output as-is
+        return reference.toString(context, path, parent);
     }
 
+    /** Returns the reference of this node */
+    public Reference reference() { return reference; }
+
     @Override
-    public TensorType type(TypeContext context) {
-        // Don't support outputs of different type, for simplicity
-        return context.getType(toString());
+    public TensorType type(TypeContext<Reference> context) {
+        TensorType type = context.getType(reference);
+        if (type == null)
+            throw new IllegalArgumentException("Unknown feature '" + toString() + "'");
+        return type;
     }
 
     @Override
     public Value evaluate(Context context) {
-        if (arguments.expressions().isEmpty() && output == null)
-            return context.get(name);
-        return context.get(name, arguments, output);
+        // TODO: Context should accept a Reference instead.
+        if (reference.isIdentifier())
+            return context.get(reference.name());
+        return context.get(getName(), getArguments(), getOutput());
     }
 
     @Override
     public CompositeNode setChildren(List<ExpressionNode> newChildren) {
-        return new ReferenceNode(name, newChildren, output);
+        return setArguments(newChildren);
     }
 
 }
diff --git a/searchlib/src/main/java/com/yahoo/searchlib/rankingexpression/rule/SerializationContext.java b/searchlib/src/main/java/com/yahoo/searchlib/rankingexpression/rule/SerializationContext.java
index ba765d07094..796c13a8669 100644
--- a/searchlib/src/main/java/com/yahoo/searchlib/rankingexpression/rule/SerializationContext.java
+++ b/searchlib/src/main/java/com/yahoo/searchlib/rankingexpression/rule/SerializationContext.java
@@ -16,17 +16,11 @@ import java.util.Map;
  *
  * @author bratseth
  */
-public class SerializationContext {
+public class SerializationContext extends FunctionReferenceContext {
     
-    /** Expression functions indexed by name */
-    private final ImmutableMap<String, ExpressionFunction> functions;
-
-    /** A cache of already serialized expressions indexed by name */
+    /** Serialized form of functions indexed by name */
     private final Map<String, String> serializedFunctions;
 
-    /** Mapping from argument names to the expressions they resolve to */
-    public final Map<String, String> bindings = new HashMap<>();
-
     /** Create a context for a single serialization task */
     public SerializationContext() {
         this(Collections.emptyList());
@@ -77,17 +71,10 @@ public class SerializationContext {
      */
     public SerializationContext(ImmutableMap<String,ExpressionFunction> functions, Map<String, String> bindings,
                                 Map<String, String> serializedFunctions) {
-        this.functions = functions;
+        super(functions, bindings);
         this.serializedFunctions = serializedFunctions;
-        if (bindings != null)
-            this.bindings.putAll(bindings);
     }
 
-    /**
-     * Returns a function or null if it isn't defined in this context
-     */
-    public ExpressionFunction getFunction(String name) { return functions.get(name); }
-
     /** Adds the serialization of a function */
     public void addFunctionSerialization(String name, String expressionString) {
         serializedFunctions.put(name, expressionString);
@@ -98,17 +85,9 @@ public class SerializationContext {
         return serializedFunctions.get(name);
     }
 
-    /**
-     * Returns the resolution of an argument, or null if it isn't defined in this context
-     */
-    public String getBinding(String name) { return bindings.get(name); }
-
-    /**
-     * Returns a new context which shares the functions and serialized function map with this but has different
-     * arguments.
-     */
-    public SerializationContext createBinding(Map<String, String> arguments) {
-        return new SerializationContext(this.functions, arguments, this.serializedFunctions);
+    @Override
+    public SerializationContext withBindings(Map<String, String> bindings) {
+        return new SerializationContext(functions().values(), bindings, this.serializedFunctions);
     }
 
     public Map<String, String> serializedFunctions() { return serializedFunctions; }
diff --git a/searchlib/src/main/java/com/yahoo/searchlib/rankingexpression/rule/SetMembershipNode.java b/searchlib/src/main/java/com/yahoo/searchlib/rankingexpression/rule/SetMembershipNode.java
index a7b82f4753f..cb31219579a 100644
--- a/searchlib/src/main/java/com/yahoo/searchlib/rankingexpression/rule/SetMembershipNode.java
+++ b/searchlib/src/main/java/com/yahoo/searchlib/rankingexpression/rule/SetMembershipNode.java
@@ -2,6 +2,7 @@
 package com.yahoo.searchlib.rankingexpression.rule;
 
 import com.google.common.collect.ImmutableList;
+import com.yahoo.searchlib.rankingexpression.Reference;
 import com.yahoo.searchlib.rankingexpression.evaluation.BooleanValue;
 import com.yahoo.searchlib.rankingexpression.evaluation.Context;
 import com.yahoo.searchlib.rankingexpression.evaluation.TensorValue;
@@ -60,7 +61,7 @@ public class SetMembershipNode extends BooleanNode {
     }
 
     @Override
-    public TensorType type(TypeContext context) {
+    public TensorType type(TypeContext<Reference> context) {
         return TensorType.empty;
     }
 
diff --git a/searchlib/src/main/java/com/yahoo/searchlib/rankingexpression/rule/TensorFunctionNode.java b/searchlib/src/main/java/com/yahoo/searchlib/rankingexpression/rule/TensorFunctionNode.java
index ec6af4bb413..6c9b6bb4a98 100644
--- a/searchlib/src/main/java/com/yahoo/searchlib/rankingexpression/rule/TensorFunctionNode.java
+++ b/searchlib/src/main/java/com/yahoo/searchlib/rankingexpression/rule/TensorFunctionNode.java
@@ -2,6 +2,7 @@
 package com.yahoo.searchlib.rankingexpression.rule;
 
 import com.google.common.annotations.Beta;
+import com.yahoo.searchlib.rankingexpression.Reference;
 import com.yahoo.searchlib.rankingexpression.evaluation.Context;
 import com.yahoo.searchlib.rankingexpression.evaluation.TensorValue;
 import com.yahoo.searchlib.rankingexpression.evaluation.Value;
@@ -64,7 +65,7 @@ public class TensorFunctionNode extends CompositeNode {
     }
 
     @Override
-    public TensorType type(TypeContext context) { return function.type(context); }
+    public TensorType type(TypeContext<Reference> context) { return function.type(context); }
 
     @Override
     public Value evaluate(Context context) {
@@ -111,12 +112,13 @@ public class TensorFunctionNode extends CompositeNode {
         public PrimitiveTensorFunction toPrimitive() { return this; }
 
         @Override
-        public TensorType type(TypeContext context) {
-            return expression.type(context);
+        @SuppressWarnings("unchecked") // Generics awkwardness
+        public <NAMETYPE extends TypeContext.Name> TensorType type(TypeContext<NAMETYPE> context) {
+            return expression.type((TypeContext<Reference>)context);
         }
 
         @Override
-        public Tensor evaluate(EvaluationContext context) {
+        public <NAMETYPE extends TypeContext.Name> Tensor evaluate(EvaluationContext<NAMETYPE> context) {
             return expression.evaluate((Context)context).asTensor();
         }
 
diff --git a/searchlib/src/test/java/com/yahoo/searchlib/rankingexpression/evaluation/EvaluationTestCase.java b/searchlib/src/test/java/com/yahoo/searchlib/rankingexpression/evaluation/EvaluationTestCase.java
index e9030cf5852..f2122bb5da9 100644
--- a/searchlib/src/test/java/com/yahoo/searchlib/rankingexpression/evaluation/EvaluationTestCase.java
+++ b/searchlib/src/test/java/com/yahoo/searchlib/rankingexpression/evaluation/EvaluationTestCase.java
@@ -378,8 +378,13 @@ public class EvaluationTestCase {
     private static class StructuredTestContext extends MapContext {
 
         @Override
+        public Value get(String feature) {
+            throw new RuntimeException("Called simple get for feature " + feature);
+        }
+
+        @Override
         public Value get(String name, Arguments arguments, String output) {
-            if (!name.equals("average")) {
+            if ( ! name.equals("average")) {
                 throw new IllegalArgumentException("Unknown operation '" + name + "'");
             }
             if (arguments.expressions().size() != 2) {
diff --git a/searchlib/src/test/java/com/yahoo/searchlib/rankingexpression/evaluation/TypeResolutionTestCase.java b/searchlib/src/test/java/com/yahoo/searchlib/rankingexpression/evaluation/TypeResolutionTestCase.java
index c882c887c8d..a08d510eec4 100644
--- a/searchlib/src/test/java/com/yahoo/searchlib/rankingexpression/evaluation/TypeResolutionTestCase.java
+++ b/searchlib/src/test/java/com/yahoo/searchlib/rankingexpression/evaluation/TypeResolutionTestCase.java
@@ -3,6 +3,7 @@
 package com.yahoo.searchlib.rankingexpression.evaluation;
 
 import com.yahoo.searchlib.rankingexpression.RankingExpression;
+import com.yahoo.searchlib.rankingexpression.Reference;
 import com.yahoo.searchlib.rankingexpression.parser.ParseException;
 import com.yahoo.tensor.TensorType;
 import com.yahoo.tensor.evaluation.TypeContext;
@@ -18,12 +19,17 @@ public class TypeResolutionTestCase {
 
     @Test
     public void testTypeResolution() {
-        TypeMapContext context = new TypeMapContext();
-        context.setType("query(x1)", TensorType.fromSpec("tensor(x[])"));
-        context.setType("query(x2)", TensorType.fromSpec("tensor(x[10])"));
-        context.setType("query(y1)", TensorType.fromSpec("tensor(y[])"));
-        context.setType("query(xy1)", TensorType.fromSpec("tensor(x[10],y[])"));
-        context.setType("query(xy2)", TensorType.fromSpec("tensor(x[],y[10])"));
+        MapTypeContext context = new MapTypeContext();
+        context.setType(Reference.simple("query", "x1"),
+                        TensorType.fromSpec("tensor(x[])"));
+        context.setType(Reference.simple("query", "x2"),
+                        TensorType.fromSpec("tensor(x[10])"));
+        context.setType(Reference.simple("query", "y1"),
+                        TensorType.fromSpec("tensor(y[])"));
+        context.setType(Reference.simple("query", "xy1"),
+                        TensorType.fromSpec("tensor(x[10],y[])"));
+        context.setType(Reference.simple("query", "xy2"),
+                        TensorType.fromSpec("tensor(x[],y[10])"));
 
         assertType("tensor(x[])", "query(x1)", context);
         assertType("tensor(x[])", "if (1>0, query(x1), query(x2))", context);
@@ -31,7 +37,7 @@ public class TypeResolutionTestCase {
         assertIncompatibleType("if (1>0, query(x1), query(y1))", context);
     }
 
-    private void assertType(String type, String expression, TypeContext context) {
+    private void assertType(String type, String expression, TypeContext<Reference> context) {
         try {
             assertEquals(TensorType.fromSpec(type), new RankingExpression(expression).type(context));
         }
@@ -40,7 +46,7 @@ public class TypeResolutionTestCase {
         }
     }
 
-    private void assertIncompatibleType(String expression, TypeContext context) {
+    private void assertIncompatibleType(String expression, TypeContext<Reference> context) {
         try {
             new RankingExpression(expression).type(context);
             fail("Expected type incompatibility exception");
diff --git a/searchlib/src/test/java/com/yahoo/searchlib/rankingexpression/rule/ArgumentsTestCase.java b/searchlib/src/test/java/com/yahoo/searchlib/rankingexpression/rule/ArgumentsTestCase.java
index 867331e99ce..303135888d8 100644
--- a/searchlib/src/test/java/com/yahoo/searchlib/rankingexpression/rule/ArgumentsTestCase.java
+++ b/searchlib/src/test/java/com/yahoo/searchlib/rankingexpression/rule/ArgumentsTestCase.java
@@ -9,13 +9,13 @@ import java.util.Collections;
 import static org.junit.Assert.*;
 
 /**
- * @author <a href="mailto:simon@yahoo-inc.com">Simon Thoresen</a>
+ * @author Simon Thoresen
  */
 public class ArgumentsTestCase {
 
     @Test
     public void requireThatAccessorsWork() {
-        Arguments args = new Arguments(null);
+        Arguments args = new Arguments();
         assertTrue(args.expressions().isEmpty());
 
         args = new Arguments(Collections.<ExpressionNode>emptyList());