Hi,
I',m not sure but I think I'm allowed to post questions here showing my own work. I have the following question (not homework or anything assessed - Im revising for my final exam and this is a past paper question that i dont have model answers to).

I'd appreciate any help. I think It's relatively simple but I am unfamiliar with pascal and unsure of my own answers.

Question
a) Each of these definitions of a type is expressed in a PASCAL-like notation. For each right hand side:


1) Express it in terms of set-operations.2) Indicate one representative member of the set that it defines.3) Give its size.



TYPE

Colour = (yellow, red, blue, green);

Charr = ['a'..'z'];

Integerr = [1..99];

String = ARRAY[0..10] OF Charr;

Info = RECORD

I : Integerr;

S : String;

C : Colour;

END (*RECORD*);

vrec = RECORD

CASE card : CARDINAL OF

0 : I : Integerr;

|1 : C : Colour;

|2 : CC : Charr;

END (*CASE*);

END (*RECORD*);

hue = SET OF Colour;



My Answers

1) Express it in terms of set-operations.

(yellow, red, blue, green)
={ (x1, x2, x3, x4)| x1 Î yellow, x2 Î red, x3 Î blue, x4 Î green}} ???

['a'..'z']
={ a|aÎ {a,b,c, …, z}}

[1..99]
={ a|aÎ {1, 2, 3, 4, …, 99} }

ARRAY[0..10] OF Charr;={ [a0, a2, …, a10]| aiÎ Charr}


Info = RECORD
I : Integerr;
S : String;
C : Colour;
END (*RECORD*);={ I, S, C | IÎ Integerr, SÎString, CÎColour }



vrec = RECORD
CASE card : CARDINAL OF
0 : I : Integerr;|1 : C : Colour;|2 : CC : Charr;
END (*CASE*);
END (*RECORD*);=?????? ???????

?=Check cardinality of ‘card’:

If 0 then assign I as integer

If 1 then assign C as Colour

If 2 then assign CC as Charr




hue = SET OF Colour;
={ x | x Î (yellow, red, blue, green)



2) Indicate one representative member of the set that it defines.


(yellow, red, blue, green)
=(yellow, red, blue, green) ???

['a'..'z']=‘a’

[1..99]=1

ARRAY[0..10] OF Charr;
=[a, b, c, d, e, f, g, h, I, j]


Info = RECORD
I : Integerr;
S : String;
C : Colour;
END (*RECORD*);
={I=1, S=[a, b, c, d, e, f, g, h, I, j], C=(yellow, red, blue, green)}


vrec = RECORD
CASE card : CARDINAL OF
0 : I : Integerr;|1 : C : Colour;|2 : CC : Charr;
END (*CASE*);
END (*RECORD*);
=?????????????

hue = SET OF Colour;
={ (x1, x2, x3, x4)| xi Î Colour}



OK. Phew!!

vrec = Im stuk with this. Although I have worked out that:
------------------------------
vrec = RECORD
CASE card : CARDINAL OF
0 : I : Integerr;
|1 : C : Colour;
|2 : CC : Charr;
END (*CASE*);
END (*RECORD*);
------------------------------

Is probably equal to:

------------------------------|
vrec = RECORD
CASE card : CARDINAL OF
0 : I : Integerr;|1 : C : Colour;|2 : CC : Charr;
END (*CASE*);
END (*RECORD*);
------------------------------

The '|' sign is the logical 'or'. I'm also guessing that first the CARDINALITY of 'card' is first taken and cardinality is the number of members of the set called 'card'. Therefore when the cardinality is worked out, if it's 0 then the variable I is assigned the datatype Integerr, when its 1 the variable C is assigned the datatype Colour, and when its 2 the variable CC is assigned the datatype Charr.

As you can see i can't really answer parts 2 and 3 if im not sure of part 1. :cry:

I'd appreciate any help you can provide.

Thank you.

oh no! When i was posting the above - I copied and pasted my tables from Word to the editing screen. It seems that the borders have disappeared. Please bare with it and help me out a little!

OK. Been doing research. Got some things to add. It seems that:

Colour = (yellow, red, blue, green);

Just means that yellow, red, blue, green are all variable names, and are of type Colour. I think I've found out something about pascal records....will post back oncei get to grips with it.

Found this at a pascal site:

------------------

Enumeration

An enumeration provides a technique of setting a list of integers where each item of the list is ranked and has a specific name. For example, instead of numbers that represent players of a football (soccer) game such as 1, 2, 3, 4, 5, you can use names instead. This would produce GoalKeeper, RightDefender, LeftDefender, Stopper, Libero. The syntax of creating an enumeration is type Series_Name = (Item1, Item2, Item_n);

In our example, the list of players by their name or position would be type Players = ( GoalKeeper, RightDefender, LeftDefender, Stopper, Libero );Once the list has been created, the name you give to the list, such as Players, becomes a variable of its own.
------------------

So I'm thinking that Colour must become a variable on its own, and the enumeration probably preserves the order of the things being enumerated. Therefore the answer to 1 would be somthing like this:

{(yellow, red, blue, green)| yellow, red, blue, green al belong to Colour }