From 0fa1b091906c3ce78a051daded68ff3ea9d67c58 Mon Sep 17 00:00:00 2001
From: Johanna Stuber <johanna.stuber@gmx.net>
Date: Mon, 15 Feb 2021 16:07:59 +0100
Subject: [PATCH] use SortedSet for quantifiedVariables in TypeAbstraction so
 instantiation is predictable

---
 .../kit/typicalc/model/TypeInferenceResult.java   |  3 +--
 .../kit/typicalc/model/type/TypeAbstraction.java  | 15 +++++----------
 .../edu/kit/typicalc/model/type/TypeVariable.java | 14 +++++++++-----
 3 files changed, 15 insertions(+), 17 deletions(-)

diff --git a/src/main/java/edu/kit/typicalc/model/TypeInferenceResult.java b/src/main/java/edu/kit/typicalc/model/TypeInferenceResult.java
index 68da474..14e0bf6 100644
--- a/src/main/java/edu/kit/typicalc/model/TypeInferenceResult.java
+++ b/src/main/java/edu/kit/typicalc/model/TypeInferenceResult.java
@@ -32,8 +32,7 @@ public class TypeInferenceResult {
     protected TypeInferenceResult(List<Substitution> substitutions, TypeVariable typeVar) {
         mgu = new ArrayList<>(substitutions);
         findMGU();
-        mgu.sort(Comparator.comparing((Substitution o) -> o.getVariable().getKind()).
-                thenComparingInt(o -> o.getVariable().getIndex()));
+        mgu.sort(Comparator.comparing(Substitution::getVariable));
         finalType = findFinalType(typeVar);
     }
 
diff --git a/src/main/java/edu/kit/typicalc/model/type/TypeAbstraction.java b/src/main/java/edu/kit/typicalc/model/type/TypeAbstraction.java
index 4323ca7..6aecb1d 100644
--- a/src/main/java/edu/kit/typicalc/model/type/TypeAbstraction.java
+++ b/src/main/java/edu/kit/typicalc/model/type/TypeAbstraction.java
@@ -3,12 +3,7 @@ package edu.kit.typicalc.model.type;
 import edu.kit.typicalc.model.TypeVariableFactory;
 import edu.kit.typicalc.model.term.VarTerm;
 
-import java.util.Arrays;
-import java.util.Collections;
-import java.util.HashSet;
-import java.util.Map;
-import java.util.Objects;
-import java.util.Set;
+import java.util.*;
 
 /**
  * Models a type abstraction with its type and the type variables bound by the for-all
@@ -17,7 +12,7 @@ import java.util.Set;
 public class TypeAbstraction {
 
     private final Type type;
-    private final Set<TypeVariable> quantifiedVariables;
+    private final SortedSet<TypeVariable> quantifiedVariables;
     /**
      * Initializes a new type abstraction with its type and the type variables bound by
      * the for-all quantifier.
@@ -26,7 +21,7 @@ public class TypeAbstraction {
      */
     public TypeAbstraction(Type type, Set<TypeVariable> quantifiedVariables) {
         this.type = type;
-        this.quantifiedVariables = quantifiedVariables;
+        this.quantifiedVariables = new TreeSet<>(quantifiedVariables);
     }
 
     /**
@@ -36,7 +31,7 @@ public class TypeAbstraction {
      */
     public TypeAbstraction(Type type) {
         this.type = type;
-        this.quantifiedVariables = Collections.emptySet();
+        this.quantifiedVariables = new TreeSet<>();
     }
 
     /**
@@ -50,7 +45,7 @@ public class TypeAbstraction {
         this.type = type;
         Set<TypeVariable> varsToBeQuantified = type.getFreeTypeVariables();
         typeAssumptions.forEach((var, abs) -> varsToBeQuantified.removeAll(abs.getFreeTypeVariables()));
-        this.quantifiedVariables = varsToBeQuantified;
+        this.quantifiedVariables = new TreeSet<>(varsToBeQuantified);
     }
 
     /**
diff --git a/src/main/java/edu/kit/typicalc/model/type/TypeVariable.java b/src/main/java/edu/kit/typicalc/model/type/TypeVariable.java
index ae9d8bb..e84d60f 100644
--- a/src/main/java/edu/kit/typicalc/model/type/TypeVariable.java
+++ b/src/main/java/edu/kit/typicalc/model/type/TypeVariable.java
@@ -3,15 +3,12 @@ package edu.kit.typicalc.model.type;
 import edu.kit.typicalc.model.UnificationError;
 import edu.kit.typicalc.util.Result;
 
-import java.util.Collections;
-import java.util.HashSet;
-import java.util.Objects;
-import java.util.Set;
+import java.util.*;
 
 /**
  * Models a type variable
  */
-public class TypeVariable extends Type {
+public class TypeVariable extends Type implements Comparable<TypeVariable> {
 
     private final TypeVariableKind kind;
     private final int index;
@@ -147,4 +144,11 @@ public class TypeVariable extends Type {
     public int hashCode() {
         return Objects.hash(kind, index);
     }
+
+    @Override
+    public int compareTo(TypeVariable var) {
+        return Comparator.comparing(TypeVariable::getKind)
+                .thenComparing(TypeVariable::getIndex)
+                .compare(this, var);
+    }
 }