Concepts of Programming Languages ---- Chapter 8 Statement-Level Control Structures

Concepts of Programming Languages ---- Chapter 8 Statement-Level Control Structures

Name : Fandy Limardi
NIM : 1601210713
Lecture : Tri Djoko Wahjono, Ir., M.Sc. (D0206)
Assignment : Concept of programming languages ---- Chapter 8 Statement-Level Control Structures

Review Questions

1.   What is the definition of control structure?

  structure is a control statement and the collection of statements whose execution it controls.

2.   What did Bohm and Jocopini prove about flowcharts?

      they proved that all algorithms that can be expressed by flowcharts can be coded in a programming languages with only two control statements: one for choosing between two control flow paths and one for logically controlled iterations.

3.   What is the definition of block?

      Block is a sequence of code delimited by either braces or the do and end reserved words.

7.   Under what circumstances must an F# selector have an else clause?

      An F# selector have an “else” clause if  the “if” expression does return a value.

12. On what previous language was C’s switch statement based?
The ability to have control flow from one selectable segment to another is rarely used. C’s switch is modeled on the multiple-selection statement in ALGOL
68, which also does not have implicit branches from selectable segments

14. What are the design issues for all iterative control statements?

• How is the iteration controlled?
• Where should the control mechanism appear in the loop statement?

21. What are the design issues for all iterative control statements?

• How is the iteration controlled?
• Where should the control mechanism appear in the loop statement?

22. What is the main reason user-located loop control were invented?
It is convenient for a programmer to choose a location for loop control other than the top or bottom of the loop body. As a result, some languages provide this capability. A syntactic mechanism for user-located loop control can be relatively simple, so its design is not difficult. Such loops have the structure of infinite loops but include user-located loop exits.

23. What are the design issues for user-located loop control mechanisms?
The design issues for such a mechanism are the following:
• Should the conditional mechanism be an integral part of the exit?
• Should only one loop body be exited, or can enclosing loops also be exited?

26. What is a user-defined iteration control?

A user-defined iteration control is the one that issues a special call to the iterator, in which the iterator is called at the beginning of each iteration, and each time it is called, the iterator returns an element from a particular data structure in some specific order.

Problem Set

1.   What design issues should ne considered for two-way selection statements?
      The design issues for two-way selectors can be summarized as follows:

       ·         What is the form and type of the expression that controls the selection?

       ·         How are the then and else clauses specified?

       ·         How should the meaning of nested selectors be specified?

4.   What are the limitations of implementing a multiple selector from two-way selectors and 
      gotos?

A multiple selector can be built from two-way selectors and gotos, but the resulting structures are cumbersome, unreliable, and difficult to write and read.

5.   What are the arguments , pro and con, for Java’s approach to specify compound statements in control statements?

       ·         Compound statements are required in control statements when the body of the if or else 
             clause requires multiple statements.

       ·         Java uses braces to form compound statements, which serve as the bodies of if and else 
             clauses.

11. Explain the advantages and disadvantages of the Java switch statement, compared to C++’s switch statement.

The Java variable in the argument of a switch statement can be of type integral ( byte, short etc.), char and String( JDK 1.7 onwards), whereas in C++ the argument can be int or char.