Remove unused function

src/main/java/lambda/Function.java

@@ -79,19 +79,6 @@ public boolean hasConflict(Variable oldVar, Expression newExpr) {
         return false;
     }
 
-    /**
-     * Alpha converts the function to a new name.
-     * 
-     * @param newName the new name of the variable
-     * @return the function with the variable renamed
-     */
-    public Function alphaConvert(String newName) {
-        Function newFunction = this.deepCopy();
-        newFunction.variable.name = newName;
-        newFunction.expression.substitute(this.variable, new Variable(newName));
-        return newFunction;
-    }
-
     /**
      * @return a string representation of the function: (λvariable.expression)
      */