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> There is nothing about recursion in documentation.<br>
The only doc that I've managed to find about the subject is the link
from my initial post
(<a class="moz-txt-link-freetext" href="http://erlang.org/doc/reference_manual/functions.html#id78464">http://erlang.org/doc/reference_manual/functions.html#id78464</a>).<br>
And it says about recursion: in sub-chapter's header, in sub-chapter
itself and in the example (all in all, everywhere). Is there another
documentation that you mean?<br>
<br>
<div class="moz-cite-prefix">On 10/17/2016 03:36 PM, Dmytro
Lytovchenko wrote:<br>
</div>
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cite="mid:CAOUb9CE=2bAAzKWkheRKLmKRWWdD-T2yFMSJ+HjSC-S8J2-UHQ@mail.gmail.com"
type="cite">
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<div>There is nothing about recursion in documentation.<br>
<br>
</div>
Your module:<br>
-module(tc).<br>
-export([a/0]).<br>
a() -> b().<br>
b() -> c().<br>
c() -> z().<br>
z() -> self().<br>
<br>
Compiles to (memory dump):<br>
00007F07875A2DA8: i_func_info_IaaI 0 tc a 0.<br>
00007F07875A2DD0: i_call_only_f tc:b/0.<br>
<br>
00007F07875A2DE0: i_func_info_IaaI 0 tc b 0.<br>
00007F07875A2E08: i_call_only_f tc:c/0.<br>
<br>
00007F07875A2E18: i_func_info_IaaI 0 tc c 0.<br>
00007F07875A2E40: i_call_only_f tc:z/0.<br>
<br>
00007F07875A2E50: i_func_info_IaaI 0 tc z 0.<br>
00007F07875A2E78: self_r x(0).<br>
00007F07875A2E80: return.<br>
<br>
</div>
Note the call_only functions. These are the tail calls.<br>
<div><br>
</div>
</div>
<div class="gmail_extra"><br>
<div class="gmail_quote">2016-10-17 14:28 GMT+02:00 Salikhov
Dinislam <span dir="ltr"><<a moz-do-not-send="true"
href="mailto:Dinislam.Salikhov@kaspersky.com"
target="_blank">Dinislam.Salikhov@kaspersky.com</a>></span>:<br>
<blockquote class="gmail_quote" style="margin:0 0 0
.8ex;border-left:1px #ccc solid;padding-left:1ex">
<div bgcolor="#FFFFFF" text="#000000"> The confusing thing
is that the doc says about tail <b>recursive</b> call.<br>
For example, if I have a call chain:<br>
a() -><br>
% some code<br>
b().<br>
b() -><br>
% some code<br>
c().<br>
% ...<br>
y() -><br>
%some code<br>
z().<br>
Recursion is <b>not</b> involved here. And I'd like to
know if erlang requires (and guarantees) that all tail
callees in the chain above use the stack of the caller.<br>
AFAIU, compiler is free to not apply the optimization if
it is not stated in the specification (and it is pure luck
that the compiler does).<span class="HOEnZb"><font
color="#888888"><br>
<br>
Salikhov Dinislam</font></span>
<div>
<div class="h5"><br>
<br>
<div class="m_-5841299804546824751moz-cite-prefix">On
10/17/2016 03:00 PM, Dmytro Lytovchenko wrote:<br>
</div>
<blockquote type="cite">
<div dir="ltr">
<div>In the doc page you linked:<br>
> If the last expression of a function body
is a function call, a <strong>tail recursive</strong>
call is done.<br>
<br>
</div>
<div>Compiler will replace call opcode with a tail
call (call_last, call_ext_last, apply_last). You
can check it with "erl -S test.erl" to see
assembly, and in erl console: "l(modulename)."
to load the module then
"erts_debug:df(modulename)." to create
disassembly from BEAM VM memory (it will be a
bit different from the erl -S output).<br>
<br>
</div>
<div>See that your calls are replaced with one of:
call_last, call_ext_last, apply_last.</div>
</div>
<div class="gmail_extra"><br>
<div class="gmail_quote">2016-10-17 10:58
GMT+02:00 Salikhov Dinislam <span dir="ltr"><<a
moz-do-not-send="true"
href="mailto:Dinislam.Salikhov@kaspersky.com"
target="_blank">Dinislam.Salikhov@kaspersky.<wbr>com</a>></span>:<br>
<blockquote class="gmail_quote" style="margin:0
0 0 .8ex;border-left:1px #ccc
solid;padding-left:1ex">
<div bgcolor="#FFFFFF" text="#000000">
<div
class="m_-5841299804546824751m_-6524208612865981557moz-text-flowed"
style="font-family:-moz-fixed;font-size:12px" lang="x-unicode">Hello. <br>
<br>
Erlang guarantees tail recursion
optimization and states it in the
documentation: <br>
<a moz-do-not-send="true"
class="m_-5841299804546824751m_-6524208612865981557moz-txt-link-freetext"
href="http://erlang.org/doc/reference_manual/functions.html#id78464"
target="_blank">http://erlang.org/doc/referenc<wbr>e_manual/functions.html#<wbr>id78464</a>
<br>
<br>
Does erlang guarantee that tail call
optimization is done in a generic case,
without recursion? <br>
Say, we have a function calling a function
from another module as its final
statement: <br>
alpha() -> <br>
xxx:beta(). <br>
Is it guaranteed that xxx:beta() will use
the stack of alpha() regardless whether
recursion is involved. <br>
I mean whether the language guarantees it
rather than virtual machine may provide
such optimization. <br>
<br>
Thanks in advance, <br>
Salikhov Dinislam <br>
</div>
</div>
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</blockquote>
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