TOPS-20 PASCAL Language Manual - Bitsavers

PASCAL DATA TYPES
Sets are compatible if their base types are identical or equivalent,
for example:
TYPE Vitamins = SET OF (A, B1, B2, B6, B12, C, D, E, K),
Nutrients = Vitamins;
VAR Watersoluble, Fatsoluble Vitamins,
Def:i. c i (o:o)folt : Nut J' i f.o)nts;
The VAR section specifies three mutually compatible sets.
compatible base types are also compatible, for example:
Sets wi th
VAR
ASCII : SET OF CHAR;
S pee i a 1. ~:; : SET (] F I! 1 • + 1 / I;
These two sets ~re compatible because the base type of Specials is
compatible with the ASCII character set.
Packing has no effect on set compatibility except when passing sets as
VAR parameters. An unpacked set is compatible with a packed set if
both sets meet the criteria above.
You can build set expressions by using the set operators described in
Chapter 3. Set operators allow you to specify set intersection,
difference, union, inclusion, and containment. In addition, you can
assign a set expression to a set variable. The base type of the
variable must include all members of the set to which the expression
eval ua tes.
Example 1
TYPE Caps = SET OF CHAR,
VAR Vowel: Caps:= [/A/,/E/,/I/,/O/,/U'];
ConsDnant : Caps := £: 'B' + + '[I', 'F' + + 'H',' J'. + 'N',
'P' •• 'T','V' •• 'Z'];
These declarations specify the set type Caps and two set variables,
Vowel and Consonant. The set Vowel is initialized with the set of
vowel characters as initial values. The set Consonant is initialized
with the set of consonants.
Example 2
VAR Ages
This example declares and initializes a set with an integer base type.
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