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Date: Tue, 17 Nov 2015 13:42:00 -0800 (PST)
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Subject: Re: Haskell, anyone?
From: Hadrien Grasland <hadrien.grasland@gmail.com>
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Xref: news.eternal-september.org comp.lang.ada:28426
Date: 2015-11-17T13:42:00-08:00
List-Id: <comp.lang.ada>

Le mardi 17 novembre 2015 19:04:53 UTC+1, Paul Rubin a =E9crit=A0:
> > I would say that recursion is the goto statement of functional
> > programming languages : necessary in order to achieve
> > Turing-completeness, and occasionally useful, but makes control flow
> > messy and programs very difficult to reason about,
>=20
> No that's continuations ;-).  Recursion works fine and is simpler
> than loops to reason about and simple to use.

Consider these two C code snippets:

int iterate_recursion(int n) {
...if (n < 2) {
......return 1;
...} else {
......return iterate_recursion(n-1);
...}
}

int iterate_goto(int n) {
...beginning:
...if (n < 2) {
......return 1;
...} else {
......n =3D n-1;
......goto beginning;
...}
}

You have to admit that in the end, the basic approach is almost exactly the=
 same, and people will need to reason about it in exactly the same way ("ok=
ay, so at the start of the iteration, the input parameter is indeed n, but =
after that, we'll decrement it and go back to the beginning of the function=
, this time with the input parameter equal to n-1, and then...").

Hence my claim that recursion is, indeed, the ultimate goto, including when=
 it comes to ease of understanding. Guy Steele will be most pleased.