NetNews Offline 2/NetNews Offline Volume 2.iso/news/comp/lang/c-part2/13808

Internet Message Format | 1996-08-05 | 2.5 KB

Path: mail2news.demon.co.uk!genesis.demon.co.uk
From: Lawrence Kirby <[e-mail]>
Newsgroups: comp.lang.c
Subject: Re: Recursion
Date: Wed, 10 Apr 96 11:54:12 GMT
Organization: none
Message-ID: <[e-mail]>
References: <[e-mail]> <[e-mail]> <4k10q0$[e-mail]> <4k4n40$[e-mail]>
Reply-To: [e-mail]
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In article <4k4n40$[e-mail]>
           [e-mail] "Dann Corbit" writes:

>In article <4k10q0$[e-mail]>, [e-mail] says...
>>
>>Lawrence Kirby ([e-mail]) wrote:
>>
>>: I think you've picked a bad example. You really need an extra argument in
>>: this case to pass on a running accumulator. A more suitable problem would
>>: be to write a recursive function that is passed an integer (unsigned is
>>: easiest) and writes the character representation to stdout.
>>Absolutely WRONG.  The whole point of recursion is that you do not need a
>>running accumulator.  When written correctly, the return value of each
>>recursive loop will be the correct accumulated value.  ANyhow, here is a
>>better version of what I already posted...
>>
>>#include <stdio.h>
>>#include <stdlib.h>
>>#include <string.h>
>>#include <math.h>
>>
>>int convert(char *string)
>> {
>>  int value;
>>  int len = strlen(string);
>>
>>  if (string[0] == '\0')
>>    return(0);
>>  value = convert(string+1);
>>  value += ((string[0] - '0') * pow(10,len-1));
>>  return(value);
>> }
>>
>>void main()
>> {
>>  char *string = "1234";
>>
>>  printf("%d\n",convert(string));
>> }
>
>I have to agree, with Mr. Kirby that recursion is a most
>inelegant way to do this.  Here is another ugly recursive
>solution.  The elegant way is atoi().  Iterative is next
>best.  Recursive is downright silly.  But we all have our
>silly moments.

I'm not saying that recursion is inelegant. I'm saying that the elegant
way to solve this problem recursively is to use an accumulator. IMHO
Bill's is the most elegant solution posted so far (and uses an accumuator),
and not just because it is short. Elegance is one of recursion's great
strengths (when it is done right), however its practicality (at least in C)
is weaker.

...

>void main( )

There's no need to copy bad code! :-)

--
-----------------------------------------
Lawrence Kirby | [e-mail]
Wilts, England | [e-mail]
-----------------------------------------