MATLAB Central Newsreader - do while

do while

Deo — Thu, 15 May 2008 08:43:02 -0400

is there a matlab command equivalent to the C do while

Re: do while

French Caro — Thu, 15 May 2008 09:14:02 -0400

"Deo " <spliers@hotmail.com> wrote in message
<g0gt2m$h3q$1@fred.mathworks.com>...
> is there a matlab command equivalent to the C do while
help while

Re: do while

Deo — Thu, 15 May 2008 09:23:02 -0400

"French Caro " <caro95470@nospam.free.fr> wrote in message
<g0gusq$425$1@fred.mathworks.com>...
> "Deo " <spliers@hotmail.com> wrote in message
> <g0gt2m$h3q$1@fred.mathworks.com>...
> > is there a matlab command equivalent to the C do while
> help while
That was the first place I looked and there was nothing
that could help me

Re: do while

John D'Errico — Thu, 15 May 2008 10:16:02 -0400

"Deo " <spliers@hotmail.com> wrote in message
<g0gvdm$5tj$1@fred.mathworks.com>...
> "French Caro " <caro95470@nospam.free.fr> wrote in message
> <g0gusq$425$1@fred.mathworks.com>...
> > "Deo " <spliers@hotmail.com> wrote in message
> > <g0gt2m$h3q$1@fred.mathworks.com>...
> > > is there a matlab command equivalent to the C do while
> > help while
> That was the first place I looked and there was nothing
> that could help me

Then you did not look hard enough.

Look again. Read the examples.

John

Re: do while

French Caro — Thu, 15 May 2008 11:44:02 -0400

"Deo " <spliers@hotmail.com> wrote in message
<g0gvdm$5tj$1@fred.mathworks.com>...
> "French Caro " <caro95470@nospam.free.fr> wrote in message
> <g0gusq$425$1@fred.mathworks.com>...
> > "Deo " <spliers@hotmail.com> wrote in message
> > <g0gt2m$h3q$1@fred.mathworks.com>...
> > > is there a matlab command equivalent to the C do while
> > help while
> That was the first place I looked and there was nothing
> that could help me

Can you explain more ?
I don't know about "do while" in C but I think that it
should be the same as "while" in MATLAB.

Caroline

Re: do while

CandyGirl — Thu, 15 May 2008 13:14:04 -0400

Yes there is,

A=5
B=2

while(A > B)
C = (A+B)/2
B=B+1
end

hope that helped

Re: do while

Dave Robinson — Thu, 15 May 2008 14:31:02 -0400

CandyGirl <Rasha@dqnetwork.com> wrote in message
<16944196.1210857274898.JavaMail.jakarta@nitrogen.mathforum.
org>...
> Yes there is,
>
>
> A=5
> B=2
>
> while(A > B)
> C = (A+B)/2
> B=B+1
> end
>
> hope that helped

The 'C' family has both
while(test)
{

}

and

do
{

}while(test)

they are different. With the while loop, if test is false
the code in the curlies is bypassed, if it is true it is
continuously looped until it becomes false, With the do -
while construct the code in the curlies is always executed
at least once, then the value of test controls whether the
code is reexecuted, the two constructs are slightly
different animals.

There is probably a much better way of doing it, but
perhaps the following abomination might give you the
functionality you need.

while(true) %Loop forever
    Your code
    if(!test)
      break;
    endif
endwhile

Regards

Dave Robinson

Re: do while

Jos — Thu, 15 May 2008 14:39:03 -0400

"Deo " <spliers@hotmail.com> wrote in message
<g0gt2m$h3q$1@fred.mathworks.com>...
> is there a matlab command equivalent to the C do while

There is a subtle difference between a "do-while" loop and
"while" loop:
do-while executes the loop at least once, whereas while may
skip the loop altogether

A work-around:

% an infinite for-loop
for i=1:Inf,
   % ... code ...
   if ~condition,
     break ; % break out of the for-loop
   end
end

hth
Jos

Re: do while

Bryan — Thu, 15 May 2008 14:52:02 -0400

Couldn't you also just do the following:

%execute commands

while (test)
%execute commands
end

By executing the code first outside the while loop, you're
ensuring that it gets executed once even if test is never
true, just as a do-while loop will do. You'll probably
have to change the (test) part of the loop a bit, but you
should be able to get the functionality you want with a
simple while loop.

Re: do while

Steve Amphlett — Thu, 15 May 2008 16:40:19 -0400

"Deo " <spliers@hotmail.com> wrote in message
<g0gt2m$h3q$1@fred.mathworks.com>...
> is there a matlab command equivalent to the C do while

Another abomination:

first=true;
while(condition || first)

% stuff

first=false;
end

Re: do while

roberson@ibd.nrc-cnrc.gc.ca (Walter Roberson) — Thu, 15 May 2008 16:57:42 -0400

In article <g0hp1j$k93$1@fred.mathworks.com>,
Steve Amphlett <Firstname.Lastname@Where-I-Work.com> wrote:
>"Deo " <spliers@hotmail.com> wrote in message
><g0gt2m$h3q$1@fred.mathworks.com>...
>> is there a matlab command equivalent to the C do while

>Another abomination:

>first=true;
>while(condition || first)

>% stuff

>first=false;
>end

Evaluating condition might have side effects. To match do while
those side effects should not be triggered on the first trip.
Therefore the above should be rewritten to

first=true;
while(first || condition)
% stuff
first=false;
end
--
   So you found your solution
   What will be your last contribution?
   -- Supertramp (Fool's Overture)

Re: do while

Steven Lord — Thu, 15 May 2008 17:47:51 -0400

"Walter Roberson" <roberson@ibd.nrc-cnrc.gc.ca> wrote in message
news:g0hq26$q1o$1@canopus.cc.umanitoba.ca...
> In article <g0hp1j$k93$1@fred.mathworks.com>,
> Steve Amphlett <Firstname.Lastname@Where-I-Work.com> wrote:
>>"Deo " <spliers@hotmail.com> wrote in message
>><g0gt2m$h3q$1@fred.mathworks.com>...
>>> is there a matlab command equivalent to the C do while
>
>>Another abomination:
>
>>first=true;
>>while(condition || first)
>
>>% stuff
>
>>first=false;
>>end
>
> Evaluating condition might have side effects. To match do while
> those side effects should not be triggered on the first trip.
> Therefore the above should be rewritten to
>
> first=true;
> while(first || condition)
> % stuff
> first=false;
> end

Alternately, you could use this:

done = false;
while ~done
    % your code
    if ~condition
        done = true;
    end
end

The condition isn't evaluated until after the loop has executed at least
once, and it's evaluated after the loop execution each subsequent time.

--
Steve Lord
slord@mathworks.com

Re: do while

helper — Thu, 15 May 2008 17:57:01 -0400

> Alternately, you could use this:
>
> done = false;
> while ~done
> % your code
> if ~condition
> done = true;
> end
> end

Or another method

while true
  % your code
  if condition
    break
  end
end

Re: do while

Dave Robinson — Fri, 16 May 2008 13:45:03 -0400

"helper " <spamless@nospam.com> wrote in message
<g0hthd$m6b$1@fred.mathworks.com>...
> > Alternately, you could use this:
> >
> > done = false;
> > while ~done
> > % your code
> > if ~condition
> > done = true;
> > end
> > end
>
>
> Or another method
>
> while true
> % your code
> if condition
> break
> end
> end

Am I missing something - how does this differ from my
original abomination?

Regards

Dave Robinson