TOPS-20 PASCAL Language Manual - Bitsavers

PASCAL DATA TYPES
Records of differing types are compatible if they meet the following
criteria:
• They have the same number of fields.
• Corresponrling field types are compatible.
•
Both are packed, or neither is
packed, corresponding fields
equal bounds.
packed. If
of subrange
the types are
types must have
The following type is also compatible with Life and Plantlife:
TYPE Coords = RECORD
X : INTEGER,
Y : O •• lOO
END;
The integer subrange O .. 100 is compatible with the type INTEGER.
However, PASCAL does not check for valid assignments to fields of
subrange types. If you assign a record of type Life to a record of
type Coord, you must ensure that the value of the field Died is within
the subrange O .• 100. An out-of-range assignment does not result in an
error message.
If the records have variants, these criteria also apply:
• The records must have the same number of variants.
• Corresponding variants must have the same number of fields.
• Corresponding field types within corresponding variants must
be compa t i bl e.
• The case labels associated with the variants must agree in
number, but need not agree in value.
• Corresponding variants in structurally compatible records
must have identical tag constant values.
• The tag constant lists in each record must be identical.
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