Well-known utility functions may be assumed to be available. 3 (TURN OVER) CST.2016.1.4 SECTION B 3 Object-Oriented Programming Java generics allows an ArrayList object to be constrained to use a single specific type (e.g. ArrayList). However, some applications require the ability to store objects of multiple unrelated types. In this question the aim is to store Integer objects alongside LinkedList objects. (a) One solution is to use ArrayList, since all Java objects extend Object. Explain why this is bad practice. [2 marks] (b) Seeking to provide a solution that allows an arbitrary set of constrained types, a programmer writes an abstract ConstrainedArray base class. To use it, the class is extended and a specialised void add(...) method should be provided for each acceptable type. public abstract class ConstrainedArray { protected ArrayList mArray = new ArrayList(); public Object get(int idx) {return mArray.get(idx);} public int size() { return mArray.size(); } } (i) Show how to a class IntListArray that extends this base class and accepts only Integer or LinkedList objects. Where appropriate, objects should be copied on insertion. [4 marks] (ii) Describe a sequence of events that would allow external modification of an object stored within an IntListArray, despite correct copying on insertion. How could this be addressed in IntListArray? [3 marks] (iii) By adding protected void add(Object o) {mArray.add(o);} to the ConstrainedArray class, the mArray field can be made private. Show how this would affect your IntListArray class and discuss the advantages of the change from protected to private. [5 marks] (c) The solutions in parts (a) and (b) both involve a get() method returning an Object reference. (i) Explain why this is bad practice. [1 mark] (ii) Propose an alternative solution for a constrained array of Integer or LinkedList objects (only) that addresses this issue. [5 marks] 4 CST.2016.1.5 4 Object-Oriented Programming (a) Using example Java code, distinguish between overloading, overriding and shadowing when applied to Java methods. 2 ) Consider different versions of an optimising compiler, each of which uses IEEE standard representation for all variables. Give two reasons why they might compile a floating-point program into code that, when run, produces differing results. [2 marks] 6 CST.2016.1.7 6 Numerical Methods A picnicker brings hot black coffee and cold milk in two identical insulated flasks and then mixes them for his drink. His friend claims that the drink would have ended up the same temperature if he had mixed the two at home and brought one flask. Note: The temperature of an object is the heat energy within it divided by its heat capacity. The rate of heat energy flow from a hotter to a cooler object is their temperature difference divided by their insulation resistance. When two fluids are mixed the resultant temperature is the sum of their initial temperatures weighted by their proportions. (a) Give a suitable state vector for a simple, finite-difference, time domain simulation of the drink system. [3 marks] (b) List the initial values and any other parameters that are needed for the simulation. Questions: Part 1: We have now established a Hive table "Company" and Two Spark Dataframe SQL accessible views "Salesworth" and "Empview" we are now in a position to provide some analysis on Mrs adebabamo's ask. Give a brief and rudimentary clarification of the standards of how the language. coming about because of part (b) may be utilized to a sentence structure analyser taking a token stream as information (by means of calls to work lex()) and giving as result an theoretical language structure tree relating to. (a) What is the principal difference between a CAM and a RAM? [4 marks] (b) What is the difference between fully associative, set associative and direct mapped lookup? [6 marks] (c) Why are TLBs always much smaller than caches? [4 marks] (d) Which of the lookup mechanisms in part (b) is usually used for a TLB and why aren't the other mechanisms usually used? [6 marks] 2 ECAD Consider the following mysterious Verilog module. module mystery(c,r,a,s); input c,r,a; output [2:0] s; reg [2:0] s; always @(posedge c or posedge r) if(r) s<=0; else begin if(a && (s<7)) s<=s+1; else if(!a && (s>0)) s<=s-1; end endmodule (a) How many flip-flops will be required to implement the mystery module, and how will signals c and r be connected to these flip-flops? [5 marks] (b) What is the state transition diagram for this mystery module? [5 marks] (c) If this module were synthesised to the minimum sum of products form, what would the equations be for next state bits s[0], s[1] and s[2]? [10 marks] 2 CST.2004.3.3 3 Data Structures and Algorithms Compiler Construction Programming answers should be written in some notation approximating SML or OCaml. (a) Describe what is meant by tail recursion. [4 marks] (b) Eliminate tail recursion from foldl given below. Consider different versions of an optimising compiler, each of which uses IEEE standard representation for all variables. Give two reasons why they might compile a floating-point program into code that, when run, produces differing results. [2 marks] 6 CST.2016.1.7 6 Numerical Methods A picnicker brings hot black coffee and cold milk in two identical insulated flasks and then mixes them for his drink. His friend claims that the drink would have ended up the same temperature if he had mixed the two at home and brought one flask. Note: The temperature of an object is the heat energy within it divided by its heat capacity. The rate of heat energy flow from a hotter to a cooler object is their temperature difference divided by their insulation resistance. When two fluids are mixed the resultant temperature is the sum of their initial temperatures weighted by their proportions. (a) Give a suitable state vector for a simple, finite-difference, time domain simulation of the drink system. [3 marks] (b) List the initial values and any other parameters that are needed for the simulation. c) Suppose that the following rules are proposed as possible optimizations to be implemented in your compiler. expression simplifies to expression (fst e, snd e) e fst (e1, e2) e1 snd (e1, e2) e2 Describe how you could implement these rules so that the simplifications are made only when the program's semantics is correctly preserved. [5 marks] 5 (TURN OVER) CST.2016.3.6 5 Concepts in Programming Languages (a) Explain what is meant by a monad in a programming language, giving the two fundamental operations of a monad along with their types. [3 marks] (b) Consider the use of a monad for input-output. For the purposes of this question, take the IO monad as including two operations readint and writeint which respectively read integers from stdin and write integers to stdout. Give the types of these operators. [2 marks] (c) Assume MLreadint and MLwriteint are primitives with side effects for inputoutput and consider the ML expression add1 of type int: let val x = MLreadint() in MLwriteint(x+1); x end (i) Give an equivalent expression which uses the IO monad instead of side-effects, and state its type. [3 marks] (ii) Give a function run2diff which can be applied to your answer to part (c)(i). When so applied it should give a value in the IO monad which corresponds to ML code that runs add1 twice and returns the difference between the values read. [4 marks] (d) State what happens when attempting to compile and execute the following Java fragment (explaining the origin of any error messages or exceptions which might arise). Object n = new Integer(42), o = new String("Whoops"); Object [] v; Integer [] w = new Integer[10]; v = w; v[4] = n; v[5] = o; [4 marks] (e) Consider the Java code: Object n = new Integer(42); ArrayList v1; ArrayList v2; ArrayList w = new ArrayList<>(10); Explain any differences in behaviour between assignments v1 = w and v2 = w and also between method calls v1.set(4,n) and v2.set(4,n). [4 marks] 6 CST.2016.3.7 6 Further Java (a) Describe the operation of wait() and notifyAll()