[erlang-questions] The history of recursion in languages. Any stories from erlang?

Bhasker Kode bosky101@REDACTED
Thu Oct 9 15:59:56 CEST 2014

another erlang specific question.


      X ->

both the above functions are tail-call optimized and happen to be recursive.

if i run foo(), would its callstack remain unchanged? will beam bring it down?
how does it compare with the procedural while (1) { //do something }


On Tue, Oct 7, 2014 at 12:42 PM, zxq9 <zxq9@REDACTED> wrote:
> Bah... forgot to send to list...
> On Tuesday 07 October 2014 18:14:32 Richard A. O'Keefe wrote:
>> It is someone 'revisionist' to suggest that looping constructs
>> are the innovation.  For example, look at
>> http://bitsavers.informatik.uni-stuttgart.de/pdf/ibm/650/28-4028_FOR_TRANSIT
>> .pdf the reference manual for the FOR TRANSIT programming language
>> on the IBM 650, developed in 1958.
>> The control statements of FOR TRANSIT included
>>     GOTO label               ! simple goto
>>     GOTO (label,...), index  ! switch
>>     IF (expr) neg,zro,pos    ! 3-way conditional (on sign)
>>     DO label var = first,last[,step] ! loop
> This (and your other) examples illustrate the exact point I am trying to make.
> The original demonstrations of what a computable thing is were recursive as
> per Church's work in 1936 -- before the machines even existed (but "computer"
> meant an office girl armed with a calculation machine who knew how to execute
> prose or formal algorithms). McCarthy published his LISP specification in 1958
> (the same year as FOR TRANSIT which contains that DO instruction). Plankalkül
> had procedure definitions in 1945.
> To say that Algol 60 "introduced recursion to many programmers" I think is a
> bit of a stretch. Recursion was very well established, even at the root of,
> computing theory.
> It seems, though, that while recursion is simply the way things were noted
> from very early on, with machines that lacked languages entirely one was
> forced to plot jumps manually, which I can easily see would lead directly to
> development of a GOTO as an early language construct before loop or procedure
> definitions came along. From there the common pattern of "GOTO label_a ... IF
> NOT b GOTO label_a" would quickly emerge -- not from the theoretical folks,
> but from the technical folks who are trying to abstract their most common
> patterns in complex control words within their early languages.
> From there it probably *did* take some time before folks who worked with
> machines worked out a formal, reliable method for optimizing recursive calls
> outside of the lisp machines of the early 1970's.
> So I suppose its really a question of whether one approaches the OP's theme
> from a theoretical or technical perspective. Recursion has been around for a
> long time in the formal languages that prompted the development of the
> electric computer, but both loop constructs and recursive procedure definitions
> took a rather long time to finally be implemented on machines, with TCO outside
> of Lisp machines being the last to the party.
> I have been spoiled, being fortunate enough to start messing with computers in
> the 1980's, long after most of this was sorted.
> -Craig
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