Question About Bitwise Expression in If

[Bakulesh Thakker]

In following code control should not got to ReplaceMonthName SUB but only first "If" works correctly. Can anyone explain why this is so?

%UsesMonthNames = 1
%DelimiterSlash = 2
%DelimiterDot   = 4
%DelimiterDash  = 8
%YearFirst      = 16
%YearMiddle     = 32
%YearLast       = 64
%MonthFirst     = 128
%MonthMiddle    = 256
%MonthLast      = 512
%DayFirst       = 1024
%DayMiddle      = 2048
%DayLast        = 4096
%Y2             = 8192
%Y4             = 16384

    DateFormat = 20752
    If (DateFormat And %UsesMonthNames) Then
        ReplaceMonthName D$
    End If
    If DateFormat And %UsesMonthNames Then
        ReplaceMonthName D$
    End If

[Michael Mattias]

Because that's how "short circuit" evaluation works in the compiler.

• IF A and B THEN " tests A; if A is false, B is never tested and THEN is not executed; THEN will execute whenever (and only whenever) both A and B are true.
• "IF (A AND B) THEN" first bitwise-ANDs A with B, then tests that result versus zero; if non-zero, THEN is executed. Meaning, both A and B could be TRUE, but THEN won't necessarily execute

.