On Thursday, 19 May 2016 at 13:45:18 UTC, Andrei Alexandrescu
wrote:
On 05/19/2016 08:38 AM, Steven Schveighoffer wrote:
Yep. chain uses voldemort type, map does not.
We definitely need to fix Voldemort types. Walter and I bounced
a few ideas during DConf.
1. Do the cleartext/compress/hash troika everywhere (currently
we do it on Windows). That should help in several places.
2. For Voldemort types, simply generate a GUID-style random
string of e.g. 64 bytes. Currently the name of the type is
composed out of its full scope, with some
exponentially-increasing repetition of substrings. That would
compress well, but it's just a lot of work to produce and then
compress the name. A random string is cheap to produce and
adequate for Voldemort types (you don't care for their name
anyway... Voldemort... get it?).
I very much advocate slapping a 64-long random string for all
Voldermort returns and calling it a day. I bet Liran's code
will get a lot quicker to build and smaller to boot.
Andrei
I have an Idea of reproducible, less-than-exponential time
mangling, although I don't know how actionable.
Leave mangling as is, but pretend that you are mangling something
different, for example when the input is
foo!(boo!(bar!(baz!(int))), bar!(baz!(int)), baz!(int))
pretend that you are mangling
foo!(boo!(bar!(baz!(int))), #1, #2)
Where #1 and #2 are special symbols that refer to stuff that was
**already in the name**, particularly:
#1: bar!(baz!(int))
#2: baz!(int)
Now, this is an reduction of the exponential computation time
only if you can detect repetitions before you go inside them, for
example, in case of #1, detect the existence of bar!(baz!(int))
without looking inside it and seeing baz!(int). Do you think it
could be done?
You would also need a deterministic way to assign those symbols
#1, #2, #3... to the stuff in the name.
Compression can also be done at the end if necessary to reduce
the polynomial growth.
