Re: Order of logical operations

["Warren W. Gay VE3WWG" <ve3wwg@cogeco.ca>]

Nick Roberts wrote:

> "Ed Falis" <falis@verizon.net> wrote in message
> news:opr8255wqr5afhvo@garuda.mshome.net...
>>On Fri, 04 Jun 2004 18:40:53 GMT, James Van Buskirk
>>
>>>I am curious
>>>as to how useful short-circuiting logical operators are
>>>considered to be in languages such as Ada that have both
>>>short-circuiting and non-short-circuiting operators.
>>
>>The short-circuit forms in Ada are considered to be very
>>useful for structural analysis of code during safety
>>certification (multiple condition, multiple decision analysis).
>>This is because sequentialization of the conditions reduces
>>the number of tests that would be necessary compared to
>>the simultaneous forms, where all combinations of
>>conditions would need to be exercised.
>>
>>Aside from that, I personally don't have a strong feeling
>>about the relative merits, excepting some potential
>>performance gains.
> 
> 
> Surely it's quite handy to be able to write things like the following?
> 
>    A: array (1..10) of Boolean;
>    ...
>    while i > 0 and then A(i) loop
>       ...

I find it handy for access types (for the FORTRAN folks,
the use of pointers):

if P /= null and then P.Member <= 23 then
    ...

If this were not short-circuited the P.Member access
would be problematic when P was null.
-- 
Warren W. Gay VE3WWG
http://home.cogeco.ca/~ve3wwg