[Yhc] Finfo flags

[Thomas Shackell]

Robert Dockins wrote:
> When would you use this flag?  Is this for combinators introduced, eg, 
> during lambda lifting?

I forget exactly but it's something like that. Certainly it's for things 
that were never in the source code but which the compiler has introduced 
itself.

> So this is particularly for anonymous functions, right?

Indeed.

> 
>>   FFL_PRIM_APPLY
>>      means this is the special inbuilt apply function that is so special
>>      you can't even write it in Haskell. So please trace it specially.
> 
> Is this also used for the STRING function?  Does it have other uses?

It's only used for apply because the way a Hat trace views the higher 
order application and the way the G-Machine views higher order 
application are somewhat different.

> Also, what happens if you get the flags wrong (like, set them all to 0 
> regardless of what they should be).   Is Hat the only think affected?  
> Will Hat crash if they're wrong?

Hat will be the only thing affected and it shouldn't crash it'll just 
give you an incorrect trace.

Thanks

Tom