RE: [Dev-C++] recursion

[Per W. <pw...@ia...>]

I think you got a bit confused about terminology.

Looping and iteration is actually the same thing.

However, recursion is not anything that should be specifically avoided.
It's a question of what problem to solve.

The trivial example of the faculty function seems to be the most quoted
example for the use of a loop instead of recursion, but the example is
quite bad, since it's faculty is easier to implement and runds faster as a
loop.

There are matematical rules that makes it possible to rewrite any
iterative function into a recursive function. And in the same way, any
recursive function may be converted to use state queues to store the
recursive state.

Use recursion when recursion results in faster run-time, or an easier
implementation. In other cases, select an iterative approach.

Examples where recursion faster and/or easier:
- light-tree evaluation in a ray tracer.
- parsing of mathematical expressions
- some recursively defined functions, such as Ackerman
- regular expression pattern matching


/Per W

On Fri, 14 Feb 2003, Jaap de Wolff wrote:

>
>
> > -----Original Message-----
> > From: Ioannis Vranos [mailto:no...@ho...]
> > Sent: Friday, February 14, 2003 07:25 AM
> > To: dev...@li...
> > Subject: Re: [Dev-C++] recursion
> >
> >
> > -------Original Message-------
> >
> > From: Santiago
> > Date: =D0=E1=F1=E1=F3=EA=E5=F5=DE, 14 =D6=E5=E2=F1=EF=F5=DC=F1=E9=EF=F2=
 2003 5:53:20 =F0=EC
> > To: dev-cpp-users-list
> > Subject: [Dev-C++] recursion
> >
> > Hello all,
> > Simple one: how often, critical, and necessary is the usage
> > of C++ recursion
> > in the "real world" programming field?
> >
> >
> > =3D=3D> It has its uses, but try to avoid using it. Use loops
> > instead (usually
> > iteration).
> >
> >
> >
> > Ioannis Vranos
>
> Iteration is usefull when you have to make more of the same (iterative)
> operations on the result of itself, before you have your result.
> A traditional example of anything which can't be solved without iteration=
 is
> the resolving of a regular expression.
> But of course there are more simple things which are far less complex usi=
ng
> iteration as by loops.
> As an example creating a hex string on stream.
>
> void ToHex(ostream &rstr, unsigned int n)
> {
> =09const char *HexChars =3D "0123456789ABCDEF";
> =09if (n >=3D 16)
> =09{
> =09=09ToHex(rstr, n/16);
> =09=09ToHex(rstr, n%16);
> =09}
> =09else
> =09{
> =09=09rstr << HexChars[n];
> =09}
> }
>
> Jaap
>
>
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