Minggu, 14 Desember 2014
Name : Romy Hermawan
NIM : 1801378902
Class : LD001
Lecturer: Ir. Tri Djoko Wahjono,M.Sc
REVIEW QUESTION:
6. What is unusual about Python’s design of compound statements?
Answer:
Python uses indentation to specify compound statements. For example,if x > y :
x = y
print “case 1″
equally indent statements are grouped as one compound statement.
7. Under what circumstances must an F# selector have an else clause?
Answer:
An F# selector have an “else” clause if the “if” expression does return a value.
8. What are the common solutions to the nesting problem for two-way
selectors?
Answer:
The else clause would be paired with the second then clause. The disadvantage of using a rule rather than some syntactic entity is that although the programmer may have meant the else clause to be thealternative to the first then clause and the compiler found the structure syntactically correct, its semantics is the opposite.
Another way to avoid the issue of nested selection statements is to use an alternative means of forming compound statements.
9. What are the design issues for multiple-selection statements?
Answer:
– What is the form and type of the expression that controls the selection?– How are the selectable segments specified?
– How are the case values specified?
– How should unrepresented selector expression values be handled, if at all?
– Is execution flow through the structure restricted to include just a single selectable segment?
10. Between what two language characteristics is a trade-off made when
deciding whether more than one selectable segment is executed in one
execution of a multiple selection statement?
Answer:
The C# switch statement differs from that of its C-based predecessors in two ways. First, C# has a static semantics rule that disallows the implicit execution of more than one segment. The rule is that every selectable segment must end with an explicit unconditional branch statement: either a break,which transfers control out of the switch statement, or a goto, which can transfer control to one of the selectable segments (or virtually anywhere else).
As with C, if there is no break at the end of the selected segment, execution continues into the next segment.
PROBLEM SET:
Answer:
The potential readability problem is the typing errors. It’s very possible to occur if we don’t type the code carefully.
Answer:
statement that allows multiple exits. Read the paper and write an operational
semantics description of the statement
Answer:
Operational semantics are a category of formal programming language semantics in which certain desired properties of a program, such as correctness, safety or security, are verified by constructing proofs from logical statements about its execution and procedures, rather than by attaching mathematical meanings to its terms (denotational semantics).
Answer:
The primary argument for using Boolean expressions exclusively as control expressions is the reliability that results from disallowing a wide range of types for this use. In C, for example, an expression of any type can appear as a control expression, so typing errors that result in references to variables of incorrect types are not detected by the compiler as errors. No , it would not be a good idea. Although this custom precedence sounds like increasing flexibility, requiring parentheses to show a custom precedence would impact in readability and writability of a program.
Answer:
Ada was designed for military grade software development. The idea is that whenever you modify code in such a way that a new case emerges (for example adding a new value for an enumeration type), you are forced to manually revisit (and therefore re-validate) all the case statements that analyze it. Having a "default" is risky: you may forget that there is a case somewhere where the new case should not have been handled by the default.
