Re: Simple (and probably stupid) question about for loops

[Andy Buckle]

On Tue, May 25, 2010 at 4:30 PM, Maynard Wright <address@hidden> wrote:
> On Tuesday 25 May 2010 07:42, John W. Eaton wrote:
>> On 25-May-2010, AlbFrigerio wrote:
>> | Hi everyone, I believe I'm really rusty in using Octave cause I'm trying
>> | to do a very simple thing (in my mind) but I cannot succed in it. I tried
>> | to read the guide and some posts on for loops, but I haven't managed
>> | anything.
>> |
>> | Here it is my question : is it possible to update the value of the for
>> | index inside the loop?
>> |
>> | For example, I wrote the following code :
>> |
>> | for k=1:10
>> |   k
>> |   if k==2
>> |      k=5;
>> |   endif
>> | endfor
>> |
>> | I'd like the output to be : 1 2 6 7 8 9 10 , but it always gives me 1 2 3
>> | 4 ... 10 . It sounds like the k variable in the loop to be completely
>> | different from the one used in the loop.
>>
>> It's not a different variable.  The value is reset each time at the
>> top of the loop.
>>
>> jwe
>
> Octave's behavior here differs from C.  If you write the comparable code in C
> it is possible to modify k within the loop and to produce the output that
> lacks the integers 3, 4, and 5.  This results from the definition of for() in
> terms of while() by K&R.  I haven't checked to see whether any subsequent
> developments in C or C++ have changed this, but my compilers support the K&R
> behavior.
>
> Note that this doesn't mean that Octave is wrong, just different from another
> language, something we need to keep in mind if we work in both.
>
> Maynard Wright
>
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>

Avoid loops if you can! However, the examples below might do something
like what you want.

k=0;
while (++k)<=10
 k
 if k==2
    k=5;
 end
end


for k=[1:2 6:10]
 k
endfor


-- 
/* andy buckle */