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From: Paul Rubin <no.email@nospam.invalid>
Newsgroups: comp.lang.ada
Subject: Re: Introductory Presentations, especially aimed at C++ programmers!
Date: Thu, 15 Dec 2016 23:41:00 -0800
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Date: 2016-12-15T23:41:00-08:00
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"Jeffrey R. Carter" <spam.jrcarter.not@spam.not.acm.org> writes:
> list_length ([]) ->
>    0;
> list_length ([First | Rest]) ->
>    1 + list_length (Rest).
> is considered tail recursion and is required to be optimized away, so
> that's how I was using the term.

That's not tail recursion because after the recursive call, the result
has to be passed to +.  You'd write it tail recursively something like:

    list_length(X) -> go(X, 0).

    go([], n) -> n;
    go([First|Rest], n) -> go(Rest, n+1).

That lets the compiler transform the recursive call into a jump.  I
don't remember the name of this trick of using an extra argument to make
something tail recursive, but it's idiomatic in functional programming.