actually what i like to do is take the calls from one to another but place
them in parent functions. sorta like,... from main-> to doBlock-> do first
half -> go back to doBlock with return -> depending do second half... so
then only parts of calls or 'nests' are done at once.
-----Original Message-----
From: Steve Sabram <[EMAIL PROTECTED]>
To: Palm Developer Forum <[EMAIL PROTECTED]>
Date: Thursday, June 22, 2000 2:08 PM
Subject: Re: Recursion?
>
>
>"Michael S. Davis" wrote:
>
>> On Thu, 22 Jun 2000, Charles Rezsonya wrote:
>>
>> > i keep hearing recursion should be avoided whiled devin' up an app.
what
>> > exactly does this mean? don't call too many loops or repeated
functions?
>> > any extra details or specs on what and what not to do would be
appriciated.
>> > brief is ok =)
>>
>> This has always puzzeled me also. Recursion means a routine that calls
>> itself. Computing a factorial is a classic example.
>>
>> But what confuses me is that a routine that recurses 3 times generally
>> takes up no more stack than a routine that calls another routine, which
>> calls a third routine.
>
>The overall problem with recursion in my experience isn't the utility of
it, but its often poor implementation. With heavy nesting of
>functions, you know that a function will be called only once and the stack
use is called in a consistent manner. With recursion,
>suddenly the stack use becomes data driven instead of code driven and
unknowns are introduced.
>
>>
>> It seems that the operative warning hers should be "don't nest
>> routines" too deep rather than "don't use recursion". Each time you
>> call a new function, you place a lot of data on the stack AND the stack
>> space is limited.
>>
>> In fact, it is quite possible that a routine that recurses 4 times may
>> use less stack that 3 separate routines that are nested.
>>
>> Anyone care to explain why there is a warning against "recursion" rather
>> than a warning against "nesting" of functions.
>
>It is almost a prejudice against academic coding styles and the AI
community in general. I did recursion on an piece of software to
>operate image processing for equipment that was focusing automatically upon
an image a few years ago. It was a very nice, iterative
>application and it worked fine. Each time the function was called, the
image became progressively more in focus 'til it terminated
>when the desired resolution was attained.
>
>However, when code review came up, the "senior" software guys screamed
bloody murder when they saw how I did it. Even though I was
>monitoring stack size in the loop, I was forced to rewrite the control
function in a traditional iterative for-loop because "we don't
>do that". Before I knew it, they were dramatizing about stories of system
crashes in mission critical projects in the early 80's when
>all of this stuff was just starting. They were not willing to listen to
how it could be done right. Since I was the new guy, they
>won over management.
>
>My attitude toward recursion is that if you do it, watch the use of stack
space every call and find a graceful way to exit just before
>you blow stack. Also, if it can be done in a regular iterative loop, do it
since the memory to hold the loop progression is usually
>just a single integer and no memory is used every iteration.
>
>Steve
>
>
>
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