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Lexical Elements of the DEC Text Processing Utility Language
4.9 Reserved Words
Syntax
CASE case-selector [[FROM
lower-constant-expr, TO upper-constant-expr]]
[constant-expr_1 [[,...]]] : statement [[,...]];
[constant-expr_2 [[,...]]] : statement [[,...]];
.
.
.
[constant-expr_n [[,...]]] : statement [[,...]];
[[[INRANGE] : statement [[,...]];]]
[[[OUTRANGE] : statement [[,...]];]]
ENDCASE;
The single brackets are not optional for case constants. Example 4–9 shows how
to use the CASE statement in a procedure.
CASE constant expressions must evaluate at compile time to either a keyword,
a string constant, or an integer constant. All constant expressions in the CASE
statement must be of the same data type. There are two special case constants
in DECTPU: INRANGE and OUTRANGE. INRANGE matches anything that
falls within the case range that does not have a case label associated with it.
OUTRANGE matches anything that falls outside the case range. These special
case constants are optional.
FROM and TO clauses of a CASE statement are not required. If FROM and
TO clauses are not specified, INRANGE and OUTRANGE labels refer to data
between the minimum and maximum specified labels.
Example 4–9 shows a sample procedure that uses the CASE statement.
Example 4–9 Procedure That Uses the CASE Statement
PROCEDURE grades
answers := READ_LINE ("Enter number of correct answers:",5);
answers := INT (answers);
CASE answers FROM 0 TO 10
[10] : score := "A+";
[9] : score := "A";
[8] : score := "B";
[7] : score := "C";
[6] : score := "D";
[0,1,2,3,4,5] : score := "F";
[OUTRANGE] : score := "Invalid entry.";
ENDCASE;
MESSAGE (score);
ENDPROCEDURE;
This CASE statement compares the value of the constant selector answers to
the case labels (the numbers 0 through 10). If the value of answers is any of
the numbers from 0 through 10, the statement to the right of that number
is executed. If the value of answers is outside the range of 0 through 10, the
statement to the right of [OUTRANGE] is executed. The value of score is written
in the message area after the execution of the CASE statement.
4–22 Lexical Elements of the DEC Text Processing Utility Language