Tail call elimination

BCS ao at pathlink.com
Wed Dec 3 09:46:18 PST 2008

Reply to Nick,

> "bearophile" <bearophileHUGS at lycos.com> wrote in message
> news:ggmm4n$o6d$1 at digitalmars.com...
>> - I know it's not necessary, just as closures aren't necessary in an
>> OO
>> language,
>> because you can create a class every time you may want a closure. But
>> functional
>> programmers are used to use certain idioms, such idioms they are part
>> of
>> the
>> functional style of mind (and they are useful because you can build
>> over
>> them.
>> Functional programming is all about building functions using other
>> functions). If
>> you want to push some functional-style in D (and I think it's a good
>> thing) then
>> several things are necessary (quite useful) to allow such style of
>> mind
>> (even if
>> some of them may look redundant to nonfunctional programmer, like
>> closures).
>> This is why I think things tail call elimination and a little may be
>> useful if D wants
>> to become more functional.
> Maybe I'm just too new to functional programming and tail call
> elimination, but I don't see how TCE could be needed for a functional
> frame of mind. It's just an optimization, right? And as I understand
> it, it just decreases performance hits from function call overhead and
> prevents the call stack from growing proportionally to the depth of
> recursion (or more simply, it just keeps the size of the call stack
> down). Can you provide an example situation where a lack of TCE would
> be a problem for a functional programmer?

Some not exactly function programs (Lisp programs that accept user input) 
have infinite recursion. Without TCE they will always crash sooner or later, 
with it they run just fine.

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