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Review Ques 5

1. As precisely as you can (two lines each, at most), define the following. Your definition should mention inputs,outputs and side-effects:
   • functions
   • predictes
2. Assume a purely logic language where any word starting with upper case is an unbound variable. In that logical language what are the outputs and side-effects of the following:
   • emp(tim,42) = emp(Name,Age)
   • emp(Who,42) = emp(tom, Age)
   • emp(tom,42) = emp(tim,Age)
3. Closures
   • Define "closures"?
   • In the following, when the add variable is initialized, what are the two parts of it contents?
   • In the following, When the above add is created, then used 3 times, what is returns?

 add = (function () {
    var counter = 0;
    return function () {return counter += 1;}
})();

add();
add();
add();

4. Type inference
   • It is claimed that languages that support type inference are less buggy. Why?
   • Why might type inference be easier in Python than Java?
5. Folding
   • What is folding?
   • What does the following expression return? foldl (+) 0 [1,2,3,4,5]
6. Erlang
   • Nome one way Erlang is fundamentally different to Python.
   • Describe uses of Erlang in 2 industrial applications. What aspects of those applications lead to the use of Erlang?
7. Heuristics
   • what is YAGNI? Describe an industrial scenario where YAGNI might save development costs.
   • what is the rule of 3? Describe an industrial scenario where YAGNI might save development costs.
8. Patterns: Suppose you are working with a 3-tier architecture system for employee management. The system composed of a database layer, business logic, and GUI. Many parts of codes are reused in this system. As an example: the database needs to know the valid ranges for age and so does the GUI.
   • What design pattern might be useful for the business logic associated with this application? Give reasoning on behalf of your answer.