From ab7f56db6f300ac36d71e62bb436a440744cc0a0 Mon Sep 17 00:00:00 2001
From: Florian Steurer <florian.steurer95@gmail.com>
Date: Mon, 21 Dec 2015 15:44:13 +0100
Subject: [PATCH] martelli montanari unification (unfinished)

---
 .../unify/interfaces/IUnify.java              | 14 ++++
 .../unifynew/MartelliMontanariUnify.java      | 80 +++++++++++++++++++
 .../typeinference/unifynew/Unifier.java       |  7 ++
 3 files changed, 101 insertions(+)
 create mode 100644 src/de/dhbwstuttgart/typeinference/unify/interfaces/IUnify.java
 create mode 100644 src/de/dhbwstuttgart/typeinference/unifynew/MartelliMontanariUnify.java

diff --git a/src/de/dhbwstuttgart/typeinference/unify/interfaces/IUnify.java b/src/de/dhbwstuttgart/typeinference/unify/interfaces/IUnify.java
new file mode 100644
index 000000000..34e397384
--- /dev/null
+++ b/src/de/dhbwstuttgart/typeinference/unify/interfaces/IUnify.java
@@ -0,0 +1,14 @@
+package de.dhbwstuttgart.typeinference.unify.interfaces;
+
+import java.util.Set;
+
+import de.dhbwstuttgart.typeinference.unifynew.Unifier;
+import de.dhbwstuttgart.typinference.unify.model.MPair;
+
+/**
+ * Standard unification algorithm (e.g. Robinson, Paterson-Wegman, Martelli-Montanari, Ruzicka-Privara or Suciu)
+ * @author Florian Steurer
+ */
+public interface IUnify {
+	public Unifier unify(Set<MPair> terms);
+}
diff --git a/src/de/dhbwstuttgart/typeinference/unifynew/MartelliMontanariUnify.java b/src/de/dhbwstuttgart/typeinference/unifynew/MartelliMontanariUnify.java
new file mode 100644
index 000000000..3631ed24c
--- /dev/null
+++ b/src/de/dhbwstuttgart/typeinference/unifynew/MartelliMontanariUnify.java
@@ -0,0 +1,80 @@
+package de.dhbwstuttgart.typeinference.unifynew;
+
+import java.util.HashSet;
+import java.util.Set;
+
+import de.dhbwstuttgart.typeinference.unify.interfaces.IUnify;
+import de.dhbwstuttgart.typinference.unify.model.MPair;
+import de.dhbwstuttgart.typinference.unify.model.MPair.PairOperator;
+import de.dhbwstuttgart.typinference.unify.model.Type;
+import de.dhbwstuttgart.typinference.unify.model.TypeParams;
+
+/**
+ * Implementation of the Martelli-Montanari unification algorithm.
+ * @author Florian Steurer
+ */
+public class MartelliMontanariUnify implements IUnify {
+
+	@Override
+	public Unifier unify(Set<MPair> terms) {
+		// TODO Auto-generated method stub
+		return null;
+	}
+	
+	private boolean delete(MPair pair) {
+		return pair.getRhsType().equals(pair.getLhsType());
+	}
+	
+	private Set<MPair> decompose(MPair pair) {
+		Set<MPair> result = new HashSet<>();
+		
+		Type rhs = pair.getRhsType();
+		Type lhs = pair.getLhsType();
+			
+		if(!rhs.getName().equals(lhs.getName()) || rhs.getTypeParams().size() != lhs.getTypeParams().size())
+			return null; // conflict
+			
+		TypeParams rhsTypeParams = rhs.getTypeParams();
+		TypeParams lhsTypeParams = lhs.getTypeParams();
+			
+		for(int i = 0; i < rhsTypeParams.size(); i++)
+			result.add(new MPair(rhsTypeParams.get(i), lhsTypeParams.get(i), PairOperator.EQUALSDOT));
+
+		return result;
+	}
+	
+	private MPair swap(MPair pair) {
+		Type rhs = pair.getRhsType();
+		Type lhs = pair.getLhsType();
+		
+		if(lhs.getTypeParams().size() != 0 && rhs.getTypeParams().size() == 0)
+			return new MPair(rhs, lhs, PairOperator.EQUALSDOT);
+		return pair;
+	}
+	
+	private Unifier eliminate(MPair pair) {
+		Type rhs = pair.getRhsType();
+		Type lhs = pair.getLhsType();
+		
+		TypeParams rhsTypeParams = rhs.getTypeParams();
+		
+		for(Type t : rhsTypeParams)
+			if(lhs.equals(t))
+				return new Unifier(); //identity-"unifier"
+		
+		return new Unifier(lhs, rhs);
+	}
+	
+	private boolean check(MPair pair) {
+		Type rhs = pair.getRhsType();
+		Type lhs = pair.getLhsType();
+		
+		TypeParams rhsTypeParams = rhs.getTypeParams();
+		
+		for(Type t : rhsTypeParams)
+			if(lhs.equals(t))
+				return false;
+		
+		return true;
+	}
+}
diff --git a/src/de/dhbwstuttgart/typeinference/unifynew/Unifier.java b/src/de/dhbwstuttgart/typeinference/unifynew/Unifier.java
index ecd56cf13..4528a9346 100644
--- a/src/de/dhbwstuttgart/typeinference/unifynew/Unifier.java
+++ b/src/de/dhbwstuttgart/typeinference/unifynew/Unifier.java
@@ -13,6 +13,13 @@ public class Unifier implements Function<Type, Type> {
 		this.source = source;
 		this.target = target;
 	}
+	
+	/**
+	 * Identity function as an "unifier".
+	 */
+	public Unifier() {
+
+	}
 
 	@Override
 	public Type apply(Type t) {