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

Bhasker Kode bosky101@REDACTED
Mon Oct 6 07:28:19 CEST 2014

We erlangers, have much to thank tail recursion for many of the
benefits and constructs that it gives us.

1. Tail recursion after all is the foundation of processes. Without
which the call stack would keep growing.
2. Processes are the foundation of implementing state machines
3. And it was Lesie Lamport "Turing Award" winner and considered the
father of distributed computing, who said that distributed systems
should be represented as state machines since they're so many unknowns
and things are changing all the time.

Which is why I thought I'd give a talk about tail recursion at FuConf,
a functional programming conference next week.
=> http://functionalconf.com/ , ping me for a big discount or if
you're travelling to Bangalore for the first time )

But I was also fascinated investigating the history of recursion and
tail recursion itself.

Arguably the first programming language in which recursive procedures
were included was J. McCarthy’s LISP. However, it was added only 2/3
months before the first implementation of LISP was complete.

During the 60's, stories and conspiracies around Algol-60 run like a
bond-movie, from the accounts of Djikstra and P Naur many years later.
Its committee members calling it the "Amsterdam Plot". Resignations,
Secretly adding sentences to language drafts. Cross-country phone
calls. Much of the controversy I believe stemmed from including
recursion vs not.

- C compilers are known to tail call optimize.Talking about relatively
more modern languages:
- Python still doesn't have tail recursion although map, reduce, and
lambda's were introduced in 1994, through the work of an anonymous but
prolific early contributor.
- Java compiler doesn't tail call optimize.
- But Scala does. In fact you can define functions to be tail
recursive, and it won't compile until it "is" tail-recursive.

Which brings me to erlang. To the esteemed members of this list:

When was recursion or tail recursion introduced in erlang?
Was it a controversial decision? Was it an easy one?
Any anecdotes you'd like to share, even about inspirations for
recursion in erlang?


~Bosky | @bhaskerkode

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