_ORELSE

_ORELSE is a boolean logical operator that performs short-circuiting inclusive logical disjunction on two expressions.

Syntax

result = firstvalue _ORELSE secondvalue

Description

• A logical operation is said to be short-circuiting if the compiled code can bypass the evaluation of one expression depending on the result of another expression.
• Short-circuiting can improve performance if the bypassed expression is complex, or if it involves procedure (SUB or FUNCTION) calls.
• If the result of the first expression evaluated determines the final result of the operation, there is no need to evaluate the second expression, because it cannot change the final result. E.g. if the first expression is already true, then the second expression can't change the result anymore, it will always remain true, even if the second expression would be false. Hence, the second expression is irrelevant and never evaluated, if the first one is already true.
  • Note that any procedures involved in the second expression are not called, if the first expression is true. This behavior is intended and the reason for the better performance, but it may cause unexpected failures if you're not aware of it.
  • In fact, if any procedures in the second expression must be called regardless of the truth of the first expression, then you must use the regular OR instead.
• If either or both expressions evaluate to true, the result is true.

Availability

• 

  none

• 

  v3.13.0

• 
• 

  yes

• 

  yes

• 

  yes

Examples

Example

OR versus _ORELSE

PRINT "Trying _ORELSE" ' _ORELSE performs short-circuiting logical conjunction and hence for "strawberry", only isFruit() is called IF isFruit("strawberry") _ORELSE isRed("strawberry") _ORELSE isSeasonal("strawberry") THEN PRINT "Probably a strawberry." ELSE PRINT "Certainly not a strawberry." END IF PRINT PRINT "Trying OR" ' OR does not performs short-circuiting logical conjunction and hence all is***() functions are called IF isFruit("strawberry") OR isRed("strawberry") OR isSeasonal("strawberry") THEN PRINT "Probably a strawberry." ELSE PRINT "Certainly not a strawberry." END IF END FUNCTION isFruit%% (fruit AS STRING) PRINT "isFruit() called!" isFruit = (fruit = "strawberry") END FUNCTION FUNCTION isRed%% (fruit AS STRING) PRINT "isRed() called!" isRed = (fruit = "strawberry") END FUNCTION FUNCTION isSeasonal%% (fruit AS STRING) PRINT "isSeasonal() called!" isSeasonal = (fruit = "strawberry") END FUNCTION

Trying _ORELSE isFruit() called! Probably a strawberry. Trying OR isFruit() called! isRed() called! isSeasonal() called! Probably a strawberry.

See also

• Featured in our "Keyword of the Day" series
• _BIT, &B, _BYTE
• AND, XOR, OR
• AND (boolean), XOR (boolean), OR (boolean)
• _ANDALSO, _NEGATE
• Binary, Boolean
• Mathematical Operations

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