Subj : Re: Reversing a number
To   : comp.programming
From : Gerry Quinn
Date : Wed Sep 14 2005 11:43 am

In article <slrndieg38.16dg.willem@toad.stack.nl>, willem@stack.nl 
says...
> Gerry wrote:
> ) Essentially, that IS the problem specification.  It is, after all, the 
> ) simplest interpretation of the mathematical operation of 'reversing a 
> ) number', that is to say, determining an number that can be represented 
> ) in base-10 as the string of digits that is the reverse of the string 
> ) representing the original number.
> )
> ) How would you explain in detail the problem, without reference to 
> ) strings?
> 
> Why would I *want* to explain the problem without reference to strings ?
> That the prolem definition needs strings to be able to explain the
> requirements does *not* imply that the solution necessarily involves
> strings.
> 
> The problem definition is simply to take a number and return the result
> of reversing that number in base-10 notation.
> 
> If you want to argue that 'base-10 notation' involves strings, go right
> ahead, I won't argue with that.
> 
> But the solution (iteratively multiplying the output by ten, dividing
>  the input by ten and adding the remainder to the output until the input
>  becomes zero) does not involve strings directly.  It inputs a number and
> outputs a number.  No strings.  Unless you wish to claim that a number is
> secretly a string, of course.

Not directly, but conceptually it is all about manipulating the base-10 
string representation.  What are easily comprehensible in these terms 
turn into kludgy numeric operations instead.  When I take x % 10, I am 
determining a value that encodes a digit in the string representation.  
The right end of the string, as I look at the string representing the 
number.

- Gerry Quinn

.