TDNR without new operators or syntax changes

[Evan Laforge]

On Sat, May 28, 2016 at 3:13 AM, AntC <anthony_clayden at clear.net.nz> wrote:
>> Evan Laforge <qdunkan <at> gmail.com> writes:
>
>> ... what would happen if you tried to do records
>> just like C structs?  So e.g. a•b requires 'a' to be a record with a
>> 'b' field, and is just one identifier, no functions involved, and 'b'
>> is not a separate value.
>
> Hi Evan, um, that's the original TDNR isn't it?
> http://hackage.haskell.org/trac/haskell-prime/wiki/
> TypeDirectedNameResolution
> As per Jeremy's ref in the first post in this thread.
>
> If you're talking C then that blobby thing between a and b
> should be a dot(?) as postfix operator.
> And it is an operator, not "just one identifier".

That's why I was trying to emphasize "not an operator".  TDNR is
complicated is because the field name is a first class value, so it's
a function applied to a record, and now we have to disambiguate the
function.  I didn't meant that.

I guess C (and Java and all the others) does call "." an operator
because it parses as one and has precedence, but it works with
identifiers, not values, and has special grammar.  It's not an
operator from the haskell point of view.  The C compiler isn't doing
any overloading or disambiguation.  As far as I understand it the
implementation is straightforward.  Could ghc do something similarly
straightforward?  It already does for qualified module names, and in
the same way in M.a, ".a" is not a function that gets something out of
an M.