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Tail Calls off by default in visual studio?

f#functional scala

I noticed that the latest CTP defaults to not doing tail call elimination by default when building in visual studio (in the debug configuration). This seems to me to be a poor default, since it breaks idiomatic functional code that is carefully written to be tail recursive. I understand that it can make code more difficult to debug, but seems like ease of debugging is a poor tradeoff for breaking correct code.

In case there are folks on the fsharp team who read this, is this a choice that can be reconsidered for the final release? Otherwise we might as well be coding in scala :-P

.Reply

We put a lot of thought into this; the idea is that if you're using 'Debug', you want good debugging (so turn off tail calls that may elide stack frames that can be useful for debugging). If you want them back on, just tick the checkbox (project properties, 'build' tab, 'generate tail calls' checkbox).

It's a tough trade-off here, and you can't please everyone with defaults, so you go after what's hopefully the majority customer/scenario, and make the rest easy to configure/switch. If you need tail calls for your app correctness while debugging, then just go tick the one checkbox and you're golden.

EDIT

Here's a nice blog entry on the topic:

[link:thevalerios.net]

By brianmcn on 6/13/2009 1:12 PM (permalink)Reply