Search code examples
vb6operatorslanguage-designshort-circuiting

Why is short-circuiting not the default behavior in VB?


VB has operators AndAlso and OrElse, that perform short-circuiting logical conjunction.

Why is this not the default behavior of And and Or expressions since short-circuiting is useful in every case.

Strangely, this is contrary to most languages where && and || perform short-circuiting.


Solution

  • Because the VB team had to maintain backward-compatibility with older code (and programmers!)

    If short-circuiting was the default behavior, bitwise operations would get incorrectly interpreted by the compiler.

    The Ballad of AndAlso and OrElse by Panopticon Central

    Our first thought was that logical operations are much more common than bitwise operations, so we should make And and Or be logical operators and add new bitwise operators named BitAnd, BitOr, BitXor and BitNot (the last two being for completeness). However, during one of the betas it became obvious that this was a pretty bad idea. A VB user who forgets that the new operators exist and uses And when he means BitAnd and Or when he means BitOr would get code that compiles but produces "bad" results.