1. Recursion question?
G'day all
When a recusive function is used in Euphoria, are all the internal
variables (including anything passed into the function) put in a stack of
some kind? Ferinstance:
<NONSENSE CODE>
function myfunc(sequence bigseq)
define another_bigseq
define other variables
do stuff to bigseq and another_bigseq
if somecondition
return(myfunc(another_bigseq))
else
return(another_bigseq)
end if
end function
</NONSENSE CODE>
Do all the intermediate "values" of each iteration of the function
(including the big sequences) get pushed onto a stack? Or do I have that
wrong?
TIA
Regards
Tony
2. Re: Recursion question?
- Posted by Graeme <graemeburke at CROSSWINDS.NET>
Dec 14, 2000
-
Last edited Dec 15, 2000
At 03:16 AM 14/12/00 -0500, you wrote:
>G'day all
>
>When a recusive function is used in Euphoria, are all the internal
>variables (including anything passed into the function) put in a stack of
>some kind? Ferinstance:
>
><NONSENSE CODE>
>function myfunc(sequence bigseq)
> define another_bigseq
> define other variables
> do stuff to bigseq and another_bigseq
> if somecondition
> return(myfunc(another_bigseq))
> else
> return(another_bigseq)
> end if
>end function
></NONSENSE CODE>
>
>Do all the intermediate "values" of each iteration of the function
>(including the big sequences) get pushed onto a stack? Or do I have that
>wrong?
>
>TIA
>
>Regards
>Tony
>
>
Yes.
Private variables are the property of each instance of
a function and stay in memory until the termination of
that instance. (cool huh?;)
This recursive function returns a list of the full paths to all
files in the directory passed and its subdirectories.
include file.e
function all_files(sequence path)
-- no trailing '\' unless root dir i.e. c:\
sequence d,list
list={}
d=dir(path)
for x=1 to length(d) do
if find('d',d[x][2]) then
if d[x][1][1]!='.' then
list=list&all_files(path&'\\'&d[x][1])
end if
else
list=append(list,path&'\\'&d[x][1])
end if
end for
return list
end function
Graeme Burke
----------------------------------------------------
3. Re: Recursion question?
On Thu, 14 Dec 2000 19:38:01 +1100, Graeme <graemeburke at CROSSWINDS.NET>
wrote:
>>
>>When a recusive function is used in Euphoria, are all the internal
>>variables (including anything passed into the function) put in a stack of
>>some kind? Ferinstance:
>
>Yes.
>Private variables are the property of each instance of
>a function and stay in memory until the termination of
>that instance. (cool huh?;)
>
G'day all
Thanks, Graeme. Does that mean that a recursive function with *lots* of big
sequences and recursed *lots* of times will eat up heaps of memory? My poor
old P166 16Mb beast goes from slow to s...l...o...w after looping around
one of these things for a while. I guess running out of RAM will do that :)
Regards
Tony
4. Re: Recursion question?
Tony,
If recursion eats up too much memory in your machine, then maybe you could
find another way to do what you want other than by recursion? That might
take more code in source, but less in execution?
Dan Moyer
----- Original Message -----
From: "Tony Bucholtz" <tony_bucholtz at HOTMAIL.COM>
To: <EUPHORIA at LISTSERV.MUOHIO.EDU>
Sent: Thursday, December 14, 2000 5:26 AM
Subject: Re: Recursion question?
> On Thu, 14 Dec 2000 19:38:01 +1100, Graeme <graemeburke at CROSSWINDS.NET>
> wrote:
>
> >>
> >>When a recusive function is used in Euphoria, are all the internal
> >>variables (including anything passed into the function) put in a stack
of
> >>some kind? Ferinstance:
> >
> >Yes.
> >Private variables are the property of each instance of
> >a function and stay in memory until the termination of
> >that instance. (cool huh?;)
> >
>
> G'day all
> Thanks, Graeme. Does that mean that a recursive function with *lots* of
big
> sequences and recursed *lots* of times will eat up heaps of memory? My
poor
> old P166 16Mb beast goes from slow to s...l...o...w after looping around
> one of these things for a while. I guess running out of RAM will do that
:)
>
> Regards
> Tony
5. Re: Recursion question?
At 08:26 AM 14/12/00 -0500, you wrote:
>On Thu, 14 Dec 2000 19:38:01 +1100, Graeme <graemeburke at CROSSWINDS.NET>
>wrote:
>
>>>
>>>When a recusive function is used in Euphoria, are all the internal
>>>variables (including anything passed into the function) put in a stack of
>>>some kind? Ferinstance:
>>
>>Yes.
>>Private variables are the property of each instance of
>>a function and stay in memory until the termination of
>>that instance. (cool huh?;)
>>
>
>G'day all
>Thanks, Graeme. Does that mean that a recursive function with *lots* of big
>sequences and recursed *lots* of times will eat up heaps of memory? My poor
>old P166 16Mb beast goes from slow to s...l...o...w after looping around
>one of these things for a while. I guess running out of RAM will do that :)
>
>Regards
>Tony
>
>
Not Nesesarily.
Euphoria is pretty tricky about how it copies sequences.
Initially, it only copies a pointer to the sequence.
The sequence will only be actually copied when one of the
two(or more) variables that is assigned to it is modified.
So basically if they're read only, you can make any number
of copies of a sequence for virtually no memory overhead,
you only 'pay' for the copy when you modify it.
What are you doing? Will a local sequence of some kind
that all instances can work on do the job?
Graeme.
----------------------------------------------------
6. Re: Recursion question?
Also of note on sequences/pointers is their
effect of large structure access, consider:
for i = 1 to 10 do
setText( textbox[i], myseq[x][y][z][i] )
end for
now consider:
sequence ptr
ptr=myseq[x][y][z]
for i = 1 to 10 do
setText( textbox[i], ptr[i] )
end for
myseq[x][y][z] is not copied.
ptr is simply assigned as a pointer to that
element, which is, of course a sequence in it's
own right.
now each time the loop executes it only looks up
ptr...[i]
Graeme.
----------------------------------------------------
7. Re: Recursion question?
On Fri, 15 Dec 2000 00:47:55 +1100, Graeme <graemeburke at CROSSWINDS.NET>
wrote:
>At 08:26 AM 14/12/00 -0500, you wrote:
>>On Thu, 14 Dec 2000 19:38:01 +1100, Graeme <graemeburke at CROSSWINDS.NET>
>>wrote:
>> <SNIP!>
>
>What are you doing? Will a local sequence of some kind
>that all instances can work on do the job?
>
>Graeme.
>
>----------------------------------------------------
G'day all
Graeme, I'm not doing anything serious with this, just experimenting with
large sequences, and ran across the recursion issue sort of by accident. My
original question was more out of curiousity than needing to "fix"
something. Still, I've learnt from the replies I got, so thanks to you and
Dan for the responses.
Regards
Tony
