_ANDALSO

_ANDALSO is a boolean logical operator that performs short-circuiting logical conjunction on two expressions.

Syntax

result = firstvalue _ANDALSO 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.
• 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.
• Short-circuiting can improve performance if the bypassed expression is complex, or if it involves procedure calls.
• If both expressions evaluate to true, result is true.

Availability

• 

  none

• 

  v3.13.0

• 
• 

  yes

• 

  yes

• 

  yes

Examples

Example: AND versus _ANDALSO

DIM AS LONG index, values(1 TO 10), v FOR index = 1 TO 10 values(index) = RND * 255 NEXT index ' value of index is now > 10 PRINT "Trying _ANDALSO" ' _ANDALSO performs short-circuiting logical conjunction and hence the GetArrayValue check is completely bypassed IF index >= 1 _ANDALSO index <= 10 _ANDALSO GetArrayValue(values(), index, v) THEN PRINT "_ANDALSO: Value ="; v ELSE PRINT "_ANDALSO: Outside range." END IF PRINT PRINT "Trying AND" ' AND does not performs short-circuiting logical conjunction and hence QB64-PE will throw a runtime error: Subscript out of range IF index >= 1 AND index <= 10 AND GetArrayValue(values(), index, v) THEN PRINT "AND: Value ="; v ELSE PRINT "AND: Outside range." END IF END FUNCTION GetArrayValue%% (arr() AS LONG, idx AS LONG, value AS LONG) value = arr(idx) GetArrayValue = -1 ' return true END FUNCTION

See also

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

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