# [erlang-questions] Are recursive record definitions allowed?

Thu Jul 29 18:16:50 CEST 2010

```And you can try the book "Algorithms: A Functional Programming Approach."
Essential functional programming techniques.

On Fri, Jul 30, 2010 at 12:00 AM, James Aimonetti <
> wrote:

> I found Chris Okasaki's Purely Functional Data Structures to be
> helpful in expanding my Erlang, data structures (duh), and functional
> programming skills as well. Sometimes the conversion from imperative
> to functional doesn't match up and this book helped bridge the gap a
> bit. I should probably dust it off and go through it again :)
>
> On Thu, Jul 29, 2010 at 5:22 AM, Brian Williams <>
> wrote:
> > This is essentially what I'm doing, but using the undefined atom. Leaf
> > technically is a node that has a value, but no children. it's not
> > really the name of an empty left or right node pointer. Here, new_node
> > generates a leaf.
> >
> > new_node(Value) ->
> >    #btreenode{left = undefined, right = undefined, value = Value}.
> >
> > insert([], Tree) -> Tree;
> > insert(Value, undefined) -> new_node(Value);
> > insert(Value, Tree = #btreenode{value = Value}) -> Tree;
> > insert(Value, #btreenode{left = Left, right = Right, value =
> CurrentValue})
> >    when Value < CurrentValue ->
> >        #btreenode{left = insert(Value, Left), right = Right, value =
> > CurrentValue};
> > insert(Value, #btreenode{left = Left, right = Right, value =
> CurrentValue})
> >    when Value > CurrentValue ->
> >        #btreenode{left = Left, right = insert(Value, Right), value =
> > CurrentValue}.
> >
> > Writing somre more complicated operations and homework assignments
> > next. I have found rewriting old homework assignments from Algorithms
> > and AI classes to be very helpful in teaching myself the language.
> >
> > On Thu, Jul 29, 2010 at 7:17 AM, Fredrik Andersson <>
> wrote:
> >> On Wed, Jul 28, 2010 at 7:39 PM, Tony Arcieri <>
> wrote:
> >>> On Tue, Jul 27, 2010 at 1:28 PM, Brian Williams <>
> wrote:
> >>>
> >>>> I'm working on some algorithm analysis and am trying to define a
> >>>> fairly simple binary search tree with a record definition:
> >>>> -record(btreenode, {left = #btreenode{}, right = #btreenode{},
> value}).
> >>>
> >>>
> >>> Wouldn't you want the defaults to be for the leaf nodes, and if so,
> >>> shouldn't they be some sort of nil/null/void atom to indicate there are
> no
> >>> left/right branches?
> >>>
> >>> --
> >>> Tony Arcieri
> >>> Medioh! A Kudelski Brand
> >>>
> >>
> >> Why not even make them the atom leaf? :)
> >>
> >
> >
> >
> > --
> > Brian E. Williams
> >
> > http://www.techhouse.us/wordpress-mu/brianw
> >
> > "Never attribute to malice that which can be adequately
> > explained by stupidity." - Hanlon's Razor
> >
> > ________________________________________________________________
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> > See http://www.erlang.org/faq.html
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> >
>
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```