On Thursday, 29 September 2016 at 19:39:35 UTC, Jonathan M Davis
wrote:
The language can't stop you from doing at least some arbitrary
stuff with them (like making + do subtraction), but the whole
goal was for user-defined types to be able to act like the
built-in types, and as such, it would make no sense to alter
them towards being treated like symbols that you can do
whatever you want with.
Having `+` do subtraction isn't something you'd normally see.
It's not a use case that would normally exist.
Having `+` do addition, but do so in a database layer is a use
case that actually may exist. The operator still behaves like a
built-in type. It may perform addition as part of a SQL query,
for example.
Whether the expression `a + b` is translated into machine
language, or translated into SQL, both still perform addition. A
value represented by `a` is added to a value represented by `b`.
Whether `a` and `b` are variables in D, or columns in a database
table is irrelevant.
And as it stands, D can already do this. It's the inability to
perform an equivalent action for the expression `a > b`.
