Re: Proposal: rename Data.Map.fromAscList to Data.Map.unsafeFromAscList

Hi, On 24 apr 2009, at 14:51, Neil Mitchell wrote:

I totally disagree. unsafe/unchecked means nothing other than "beware of the bogey monster", or for most Haskell users, "just another function that might launch missiles". fromAscList has the specific precondition for this function in the name. Should we call unsafeHead? uncheckedHead? mightCrashIfNotConsHead?

No, but the functions you mentioned do fail immediately. If I use a head on an empty list I get an error immediately. If I use fromAscList incorrectly I get an error only when I try to lookup elements. This makes it hard to debug if you didn't make this error before. I don't mind a runtime error in this case, but I very much want to know where my bug is. Thanks, -chris

Thanks

Neil

On Fri, Apr 24, 2009 at 1:36 PM, Christian Maeder wrote:

...

There is an old thread about this, where Daan suggested "unchecked" instead of "unsafe". http://www.haskell.org/pipermail/haskell/2004-March/013787.html

"unsafe" reminds to "IO" stuff.

Didn't you read the comment about fromAscList? Isn't the name long enough to scare you?

Would you have not taken "unsafeFromAscList" under the same circumstances you've chosen "fromAscList"?

Cheers Christian

Chris Eidhof wrote:

...

Hey all,

I had some code where the function elems said a certain key was present, but looking it up returned a Nothing. After some debugging I found out that it did work if I used Prelude's lookup in combination with toList. After even more debugging it turned out there was a fromAscList somewhere deep down in my code where it should have been a fromList.

Now, I know that I shouldn't have used fromAscList and that it was totally my fault. I also realize this is something that can't easily be checked using the type system, so I propose we do the next best thing: prefix the name with 'unsafe'.

-chris

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