CASE

Purpose

The CASE statement initiates a CASE statement block in a CASE construct, which has a concise syntax for selecting, at most, one of a number of statement blocks for execution.

Syntax


>>-CASE--case_selector--+---------------------+----------------><
                        '-case_construct_name-'

case_selector


>>-+-DEFAULT------------------------------------------+--------><
   |    .-,--------------------------------------.    |   
   |    V                                        |    |   
   '-(----+-case_value-------------------------+-+--)-'   
          +-low_case_value--:--high_case_value-+          
          +-low_case_value--:------------------+          
          '-:--high_case_value-----------------'

case_construct_name: Is a name that identifies the CASE construct.
case_value: is a scalar constant expression of type integer, character, or logical
low_case_value, high_case_value: are each scalar constant expressions of type integer, character, or logical

Rules

The case index, determined by the SELECT CASE statement, is compared to each case_selector in a CASE statement. When a match occurs, the stmt_block associated with that CASE statement is executed. If no match occurs, no stmt_block is executed. No two case value ranges can overlap.

A match is determined as follows:

case_value: DATA TYPE:  integer, character or logical
MATCH for integer and character:  case index = case_value
MATCH for logical:  case index .EQV. case_value is
true
low_case_value : high_case_value: DATA TYPE: integer or character
MATCH: low_case_value ≤ case index ≤
high_case_value
low_case_value :: DATA TYPE: integer or character
MATCH: low_case_value ≤ case index
: high_case_value: DATA TYPE: integer or character
MATCH: case index ≤ high_case_value
DEFAULT: DATA TYPE: not applicable
MATCH: if no other match occurs.

There must be only one match. If there is a match, the statement block associated with the matched case_selector is executed, completing execution of the case construct. If there is no match, execution of the case construct is complete.

If the case_construct_name is specified, it must match the name specified on the SELECT CASE and END SELECT statements.

DEFAULT is the default case_selector. Only one of the CASE statements may have DEFAULT as the case_selector.

Each case value must be of the same data type as the case_expr, as defined in the SELECT CASE statement. If any typeless constants or BYTE named constants are encountered in the case_selectors, they are converted to the data type of the case_expr.

When the case_expr and the case values are of type character, they can have different lengths. If you specify the -qctyplss compiler option, a character constant expression used as the case_expr remains as type character. The character constant expression will not be treated as a typeless constant.

Examples

ZERO: SELECT CASE(N)

  CASE DEFAULT ZERO          ! Default CASE statement for
                             ! CASE construct ZERO
       OTHER: SELECT CASE(N)
          CASE(:-1)          ! CASE statement for CASE
                             ! construct OTHER
             SIGNUM = -1
          CASE(1:) OTHER
              SIGNUM = 1
       END SELECT OTHER
  CASE (0)
    SIGNUM = 0

END SELECT ZERO

Related information

CASE construct
SELECT CASE
END (Construct), for details on the END SELECT statement

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