CASE operator

The CASE operator creates a property that selects a result by condition.

Syntax

CASE [exclusionType]
    WHEN condition1 THEN result1
    ...
    WHEN conditionN THEN resultN
    [ELSE elseResult]

Description

The CASE operator creates a property that implements a conditional selection. Selection conditions are defined using the properties specified in the WHEN block. If the selection condition is met, the property value will be the value of the property specified in the corresponding THEN block. If none of the conditions are met, the property value will be the property value in the ELSE block, if that block is specified (if not, NULL is returned).

Parameters

• exclusionType

  Type of mutual exclusion. Determines whether several conditions can be met simultaneously for a certain set of parameters. It is specified by one of the keywords:

  • EXCLUSIVE
  • OVERRIDE

  The EXCLUSIVE type indicates that none of the conditions listed can be met simultaneously. The OVERRIDE type allows several conditions to be met simultaneously, in this case, the property value will be the value of the value property for the first met condition.

  The OVERRIDE type is used by default.

• condition1 ... conditionN

  Expressions whose values define the selection condition.

• result1 ... resultN

  Expressions whose values define the selection result.

• elseResult

  An expression whose value defines the property value if none of the conditions are met.

Examples

CLASS Color;
id = DATA STRING[100] (Color);

background 'Color' (Color c) = CASE
    WHEN id(c) == 'Black' THEN RGB(0,0,0)
    WHEN id(c) == 'Red' THEN RGB(255,0,0)
    WHEN id(c) == 'Green' THEN RGB(0,255,0)
;

id (TypeExecEnv type) = CASE EXCLUSIVE
    WHEN type == TypeExecEnv.materialize THEN 3
    WHEN type == TypeExecEnv.disablenestloop THEN 2
    WHEN type == TypeExecEnv.none THEN 1
    ELSE 0
;