Type: constrainEqualTo* implementation

src/main/java/edu/kit/typicalc/model/UnificationError.java

@@ -1,5 +1,6 @@
 package edu.kit.typicalc.model;
 
 public enum UnificationError {
-    INFINITE_TYPE
+    INFINITE_TYPE,
+    DIFFERENT_TYPES
 }

src/main/java/edu/kit/typicalc/model/type/FunctionType.java

@@ -10,8 +10,8 @@ import java.util.Objects;
  */
 public class FunctionType extends Type {
 
-    private Type parameter;
+    private final Type parameter;
-    private Type output;
+    private final Type output;
     /**
      * Initializes a new FunctionType with the given parameter and output types.
      * @param parameter the type of this function’s parameter
@@ -60,9 +60,9 @@ public class FunctionType extends Type {
      * @param type  the other type
      * @return unification steps necessary, or an error if that is impossible
      */
+    @Override
     public Result<UnificationActions, UnificationError> constrainEqualTo(Type type) {
-        //TODO
+        return type.constrainEqualToFunction(this);
-        return null;
     }
 
     /**
@@ -71,9 +71,9 @@ public class FunctionType extends Type {
      * @param type the function type
      * @return unification steps necessary, or an error if that is impossible
      */
-    public Result<UnificationActions, UnificationError> constrainEqualToFunction(Type type) {
+    @Override
-        //TODO
+    public Result<UnificationActions, UnificationError> constrainEqualToFunction(FunctionType type) {
-        return null;
+        return UnificationUtil.functionFunction(this, type);
     }
 
     /**
@@ -82,9 +82,9 @@ public class FunctionType extends Type {
      * @param type the named type
      * @return unification steps necessary, or an error if that is impossible
      */
+    @Override
     public Result<UnificationActions, UnificationError> constrainEqualToNamedType(NamedType type) {
-        //TODO
+        return UnificationUtil.functionNamed(this, type);
-        return null;
     }
 
     /**
@@ -93,9 +93,9 @@ public class FunctionType extends Type {
      * @param type the type variable
      * @return the unification steps necessary, or an error if that is impossible
      */
+    @Override
     public Result<UnificationActions, UnificationError> constrainEqualToVariable(TypeVariable type) {
-        //TODO
+        return UnificationUtil.functionVariable(this, type);
-        return null;
     }
 
     /**

src/main/java/edu/kit/typicalc/model/type/NamedType.java

@@ -18,7 +18,7 @@ public class NamedType extends Type {
 	 */
 	public static final NamedType INT = new NamedType("int");
 
-	private String name;
+	private final String name;
 
 	/**
 	 * Initializes a new NamedType with the given name.
@@ -72,9 +72,9 @@ public class NamedType extends Type {
 	 * @param type  the other type
 	 * @return unification steps necessary, or an error if that is impossible
 	 */
+	@Override
 	public Result<UnificationActions, UnificationError> constrainEqualTo(Type type) {
-		//TODO
+		return type.constrainEqualToNamedType(this);
-		return null;
 	}
 
 	/**
@@ -83,9 +83,9 @@ public class NamedType extends Type {
 	 * @param type the function type
 	 * @return unification steps necessary, or an error if that is impossible
 	 */
-	public Result<UnificationActions, UnificationError> constrainEqualToFunction(Type type) {
+	@Override
-		//TODO
+	public Result<UnificationActions, UnificationError> constrainEqualToFunction(FunctionType type) {
-		return null;
+		return UnificationUtil.functionNamed(type, this);
 	}
 
 	/**
@@ -94,9 +94,9 @@ public class NamedType extends Type {
 	 * @param type the named type
 	 * @return unification steps necessary, or an error if that is impossible
 	 */
+	@Override
 	public Result<UnificationActions, UnificationError> constrainEqualToNamedType(NamedType type) {
-		//TODO
+		return UnificationUtil.namedNamed(this, type);
-		return null;
 	}
 
 	/**
@@ -105,9 +105,9 @@ public class NamedType extends Type {
 	 * @param type the type variable
 	 * @return the unification steps necessary, or an error if that is impossible
 	 */
+	@Override
 	public Result<UnificationActions, UnificationError> constrainEqualToVariable(TypeVariable type) {
-		//TODO
+		return UnificationUtil.variableNamed(type, this);
-		return null;
 	}
 
 	@Override

src/main/java/edu/kit/typicalc/model/type/Type.java

@@ -42,7 +42,7 @@ public abstract class Type {
      * @param type the function type
      * @return unification steps necessary, or an error if that is impossible
      */
-    public abstract Result<UnificationActions, UnificationError> constrainEqualToFunction(Type type);
+    public abstract Result<UnificationActions, UnificationError> constrainEqualToFunction(FunctionType type);
 
     /**
      * Computes the necessary constraints (and substitution) to unify this type with a

src/main/java/edu/kit/typicalc/model/type/TypeVariable.java

@@ -56,6 +56,7 @@ public class TypeVariable extends Type {
      * @param b the type to insert
      * @return itself, or b if a is equal to this object
      */
+    @Override
     public Type substitute(TypeVariable a, Type b) {
         if (this.equals(a)) {
         return b;
@@ -79,9 +80,9 @@ public class TypeVariable extends Type {
      * @param type  the other type
      * @return unification steps necessary, or an error if that is impossible
      */
+    @Override
     public Result<UnificationActions, UnificationError> constrainEqualTo(Type type) {
-        //TODO
+        return type.constrainEqualToVariable(this);
-        return null;
     }
 
     /**
@@ -90,9 +91,9 @@ public class TypeVariable extends Type {
      * @param type the function type
      * @return unification steps necessary, or an error if that is impossible
      */
-    public Result<UnificationActions, UnificationError> constrainEqualToFunction(Type type) {
+    @Override
-        //TODO
+    public Result<UnificationActions, UnificationError> constrainEqualToFunction(FunctionType type) {
-        return null;
+        return UnificationUtil.functionVariable(type, this);
     }
 
     /**
@@ -101,9 +102,9 @@ public class TypeVariable extends Type {
      * @param type the named type
      * @return unification steps necessary, or an error if that is impossible
      */
+    @Override
     public Result<UnificationActions, UnificationError> constrainEqualToNamedType(NamedType type) {
-        //TODO
+        return UnificationUtil.variableNamed(this, type);
-        return null;
     }
 
     /**
@@ -112,9 +113,9 @@ public class TypeVariable extends Type {
      * @param type the type variable
      * @return the unification steps necessary, or an error if that is impossible
      */
+    @Override
     public Result<UnificationActions, UnificationError> constrainEqualToVariable(TypeVariable type) {
-        //TODO
+        return UnificationUtil.variableVariable(this, type);
-        return null;
     }
 
     @Override

src/main/java/edu/kit/typicalc/model/type/UnificationActions.java

@@ -4,14 +4,15 @@ import edu.kit.typicalc.model.Constraint;
 import edu.kit.typicalc.model.Substitution;
 
 import java.util.Collection;
+import java.util.Collections;
 import java.util.Optional;
 
 /**
  * Models the necessary actions to process a constraint.
  */
 public class UnificationActions {
-    private Collection<Constraint> constraints;
+    private final Collection<Constraint> constraints;
-    private Optional<Substitution> substitution;
+    private final Optional<Substitution> substitution;
 
     /**
      * Initializes this object using the provided constraints and substitution.
@@ -23,6 +24,14 @@ public class UnificationActions {
         this.substitution = substitution;
     }
 
+    /**
+     * Initializes an empty object.
+     */
+    protected UnificationActions() {
+        this.constraints = Collections.emptyList();
+        this.substitution = Optional.empty();
+    }
+
     /**
      * Getter for constraints
      * @return the constraints stored in this object

src/main/java/edu/kit/typicalc/model/type/UnificationUtil.java

@@ -0,0 +1,55 @@
+package edu.kit.typicalc.model.type;
+
+import edu.kit.typicalc.model.Constraint;
+import edu.kit.typicalc.model.Substitution;
+import edu.kit.typicalc.model.UnificationError;
+import edu.kit.typicalc.util.Result;
+
+import java.util.Collections;
+import java.util.List;
+import java.util.Optional;
+
+/**
+ * Utility class to avoid unification logic duplication in type methods.
+ */
+final class UnificationUtil {
+    // TODO: document class? implementation detail?
+    private UnificationUtil() {
+
+    }
+
+    // TODO: check for infinite types
+
+    static Result<UnificationActions, UnificationError> functionFunction(FunctionType a, FunctionType b) {
+        return new Result<>(new UnificationActions(List.of(
+                new Constraint(a.getParameter(), b.getParameter()),
+                new Constraint(a.getOutput(), b.getOutput())), Optional.empty()));
+    }
+
+    static Result<UnificationActions, UnificationError> functionNamed(FunctionType a, NamedType b) {
+        return new Result<>(null, UnificationError.DIFFERENT_TYPES);
+    }
+
+    static Result<UnificationActions, UnificationError> functionVariable(FunctionType a, TypeVariable b) {
+        return new Result<>(new UnificationActions(Collections.emptyList(),
+                Optional.of(new Substitution(b, a))));
+    }
+
+    static Result<UnificationActions, UnificationError> variableNamed(TypeVariable a, NamedType b) {
+        return new Result<>(new UnificationActions(Collections.emptyList(),
+                Optional.of(new Substitution(a, b))));
+    }
+
+    static Result<UnificationActions, UnificationError> variableVariable(TypeVariable a, TypeVariable b) {
+        return new Result<>(new UnificationActions(Collections.emptyList(),
+                Optional.of(new Substitution(a, b))));
+    }
+
+    static Result<UnificationActions, UnificationError> namedNamed(NamedType a, NamedType b) {
+        if (a != b) {
+            return new Result<>(null, UnificationError.DIFFERENT_TYPES);
+        } else {
+            return new Result<>(new UnificationActions());
+        }
+    }
+}