Ton,
Well that is a really poor implementation of Case, giving you no more
utility than a bunch of IF THENs. The way that Tomasz has done it is
the right way. Fall through IS the reason to have the Switch -Case -
Break -Default construct. Forget about the Foxpro ideas below.
Dennis
On May 26, 2007, at 2:46 PM, Ton Sieverding wrote:
Thanks Nigel. I have a serious problem with the following remark :
> If you leave out the break statements, and
> expression==constant_expression1 you will execute statement1
(what you
> wanted) AND ALSO statement2 AND ALSO statement3 AND ALSO ...
statementN
> AND ALSO statement_default.
So what you are telling me is that after having executed
statement1, SWITCH will execute all the other case statements too.
Because there is no break. I am using the SWITCH ( Visual Foxpro
called DO CASE ) statement and never have seen this. Once one of
the cases it true, the corresponding command will be executed and
you're leaving the SWITCH structure. There are no breaks needed to
exit SWITCH. Is this different in AFL ? Please reed underneath
mentioned help text from MS Visual FoxPro :
CASE lExpression1 Commands ... When the first true (.T.) CASE
expression is encountered, the set of commands following it is
executed. Execution of the set of commands continues until the next
CASE or ENDCASE is reached. Execution then resumes with the first
command following ENDCASE.
If a CASE expression is false (.F.), the set of commands following
it up to the next CASE clause is ignored.
Only one set of commands is executed. These are the first commands
whose CASE expression evaluates to true (.T.). Any succeeding true
(.T.) CASE expressions are ignored.
Of course what I should and will do is test what the AFL SWITCH
really does ...
Regards, Ton.
----- Original Message -----
From: "Nigel Rowe" <[EMAIL PROTECTED]>
To: <[email protected]>
Sent: Friday, May 25, 2007 12:12 PM
Subject: Re: [amibroker] Re: Nested Switch() statements
> On Fri, 25 May 2007, Ton Sieverding wrote:
> > Can you please explain me why 'switch statements are a frequent
> > source of bugs' ? If the last CASE is a DEFAULT then all possible
> > cases are covered. Or am I missing something in the AFL SWITCH
> > statement ?
> >
> > switch ( expression )
> > {
> > case constant-expression1 : statement;
> > case constant-expression2 : statement;
> > ...
> > case constant-expressionN : statement;
> >
> > default : statement;
> >
> > }
> >
> >
> > Ton.
>
> The 'standard' error when using a switch statement in 'C' and
presumably
> AFL, is forgetting to put 'break;' statements in.
>
> To paraphrase your example (above) so it looks like this:-
>
> switch ( expression )
> {
> case constant-expression1 : statement1;
> case constant-expression2 : statement2;
> ...
> case constant-expressionN : statementN;
> default : statement_default;
> }
>
> If you leave out the break statements, and
> expression==constant_expression1 you will execute statement1
(what you
> wanted) AND ALSO statement2 AND ALSO statement3 AND ALSO ...
statementN
> AND ALSO statement_default.
>
> It's sometimes called the 'fall-through' bug. It's easy to miss,
can be
> a right pain!
>
>
> --
> Nigel Rowe
> rho \N{COMMERCIAL AT} swiftdsl \N{FULL STOP} com \N{FULL STOP} au
>
>
>
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