CASE Statement

Allows conditional execution of a sequence of statements.

Syntax

BEGIN CASE
    CASE expression
    statement(s)
    CASE expression
    statement(s)
    .
    .
    .
END CASE

Syntax Elements

expression is any valid DataBasic expression that evaluates to true (non-zero) or false (0).

statement(s) is a sequence of one or more valid DataBasic statements.

Operation

CASE statements are processed in turn, commencing at the one immediately after the BEGIN CASE statement. Expressions in CASE statements are evaluated in the same way as expressions in IF statements.

If an expression is false (zero), then control passes to the next CASE statement.

If an expression is true (1), the sequence of statement(s) immediately following the CASE statement containing that expression is executed. When the next CASE statement is reached, control passes to the first statement after the END CASE statement.

If all CASE expressions are found to be false, then control passes to the first statement after the END CASE statement.

A CASE 1 condition included as the last CASE statement before END CASE (see example 1), functions like an else clause. The test expression (1) is always true and statement(s) below it will be executed if all previous CASE expressions are false.

Programs containing unmatched BEGIN CASE or END CASE statements will not compile.

Examples

BEGIN CASE

    CASE A < 5

    PRINT 'A IS LESS THAN 5'

    CASE A < 10

    PRINT 'A IS GREATER THAN OR EQUAL TO 5 AND LESS THAN 10'

    CASE 1

    PRINT 'A IS GREATER THAN OR EQUAL TO 10'

END CASE

If A<5, the first PRINT statement is executed. If 5<=A<10, the second PRINT statement is executed. Otherwise, the third PRINT statement is executed.

BEGIN CASE

    CASE A=0; GOTO 10

    CASE A<0; GOTO 20

    CASE 1; GOTO 30

END CASE

Control branches to the statement labeled 10 if A is zero, to 20 is A is negative or to 30 if A is greater than zero.

BEGIN CASE
    CASE ST MATCHES "1A"
      MAT LET=1
    CASE ST MATCHES "1N"
      SGL=1; A.1(I)=ST
    CASE ST MATCHES "2N"
      DBL=1; A.2(J)=ST
    CASE ST MATCHES "3N"
      GOSUB 103
END CASE

If ST is one letter, the value 1 is assigned to all LET elements, and the case ends. If ST is one number, then 1 is assigned to SGL, ST is stored at element A.1(I), and the case ends. If ST is two numbers, 1 is assigned to DBL, ST is stored at A.2(J), and the case ends. If ST is three numbers, subroutine 103 is executed. If none of the cases is true, control passes to the statement following END CASE.