Nested Statements.

[Profetas]

Hi,

Nested statements helps to generate complex source code,
what is the nesting limit that you normally consider?

I know that the Halsted and McCabe analyses can define the acceptable
level, but in your personnel point of views what is the limit before you
re-code the block into multiple blocks

a 3 level nesting example

If (z is true)
while (x < Y )
begin
if (z==x)
......
else
.......
end if

end
end
else

while (x < Y )
begin
if (z==x)
......
else
.......
end if

end
end

end if


I think that 3 level sometimes 4 is acceptable.
but I was wondering would you restrict it to 3 or 4?

is there anyway to avoid this excluding the creation of new functions?

Thanks

[Malcolm]

Re: Nested Statements.


"Profetas" <xuxu_18@yahoo. com> wrote[color=blue]
>
> Nested statements helps to generate complex source code,
> what is the nesting limit that you normally consider?
>[/color]
Ideally about three levels is the maximum that a human can easily read, but
in practise it isn't possible to achieve this[color=blue]
>
> is there anyway to avoid this excluding the creation of new functions?
>[/color]
No always. Even creating a new function is often not the answer. A function
should do something which is discrete and can be summarised in a short
comment. Often complex flow logic is to handle errors or similar conditions
and it is not possible to break it out into a function.
You can use goto. This is a terrible solution when badly used, but
acceptable when used carefully. eg

MYLEVEL *createlevel(ch ar *filename)
{
MYLEVEL *answer = 0;
FILE *fp = fopen("filename ", "rb");
if(!fp)
goto error;

answer = malloc(sizeof(M YLEVEL));
if(!answer)
goto error;

answer->cell = 0;
/* etc */

answer->cell = malloc(width * height);
if(!answer->cell)
goto error;

etc etc etc;

return answer;

error:
/*
code to free up a partially-allocated level
*/
return NULL;
}

[CBFalconer]

Re: Nested Statements.

Profetas wrote:[color=blue]
>
> Nested statements helps to generate complex source code,
> what is the nesting limit that you normally consider?
>
> I know that the Halsted and McCabe analyses can define the
> acceptable level, but in your personnel point of views what is the
> limit before you re-code the block into multiple blocks
>
> a 3 level nesting example
>
> If (z is true)
> while (x < Y )
> begin
> if (z==x)
> ......
> else
> .......
> end if
>
> end
> end
> else
>
> while (x < Y )
> begin
> if (z==x)
> ......
> else
> .......
> end if
>
> end
> end
>
> end if
>
> I think that 3 level sometimes 4 is acceptable.
> but I was wondering would you restrict it to 3 or 4?
>
> is there anyway to avoid this excluding the creation of new
> functions?[/color]

First, take your own example and avoid creating non-existent
levels. The 'begin's (which are '{' in C) are not a level of
control. Then limit the line length to 72 chars or so. You should
also use the rule of 7, which says that a function should deal with
no more than 7 items at once, because the human brain becomes
confused with more.

Rewriting your example into reasonable (IMO) format:

If (z is true) {
while (x < Y) {
if (z == x) ......
else .......
}
}
else {
while (x < Y) {
if (z == x) {
......
}
else {
.......
}
}
}

Which smells (to me) as if misconstructed. I suspect the .....
areas should have been parametized in some form, so that the
overall code should be simplified to:

if (z) operateon(x, y, zz);
else operateon(z, y, z);

--
Chuck F (cbfalconer@yah oo.com) (cbfalconer@wor ldnet.att.net)
Available for consulting/temporary embedded and systems.
<http://cbfalconer.home .att.net> USE worldnet address!

[Peter Pichler]

Re: Nested Statements.

"Profetas" <xuxu_18@yahoo. com> wrote:[color=blue]
> Nested statements helps to generate complex source code,
> what is the nesting limit that you normally consider?[/color]

Infinity :) Seriously, my limit would be about 20, i.e. when the indentation
reaches the middle of the screen.
[color=blue]
> a 3 level nesting example
>
> If (z is true)
> while (x < Y )
> begin
> if (z==x)
> ......
> else
> .......
> end if
> end
> end
> else[/color]

What has the above to do with C?
[color=blue]
> I think that 3 level sometimes 4 is acceptable.
> but I was wondering would you restrict it to 3 or 4?[/color]

No.
[color=blue]
> is there anyway to avoid this excluding the creation of new functions?[/color]

Yes, there is. But why? (One way could be using a lot of gotos. But then
again, why?)

Peter

[Mark McIntyre]

Re: Nested Statements.

On Sat, 6 Nov 2004 23:09:04 -0000, in comp.lang.c , "Peter Pichler"
<pichlo7@pobox. sk> wrote:
[color=blue]
>"Profetas" <xuxu_18@yahoo. com> wrote:[color=green]
>> Nested statements helps to generate complex source code,
>> what is the nesting limit that you normally consider?[/color]
>
>Infinity :)[/color]

I'd suggest 127 would be a safer limit...
5.2.4.1 Translation limits
1 The implementation shall be able to translate and execute at least one
program that contains at least one instance of every one of the following
limits:
- 127 nesting levels of blocks


--
Mark McIntyre
CLC FAQ <http://www.eskimo.com/~scs/C-faq/top.html>
CLC readme: <http://www.ungerhu.com/jxh/clc.welcome.txt >

----== Posted via Newsfeeds.Com - Unlimited-Uncensored-Secure Usenet News==----
http://www.newsfeeds.com The #1 Newsgroup Service in the World! 120,000+ Newsgroups
----= East and West-Coast Server Farms - Total Privacy via Encryption =----