On Tuesday, 12 November 2013 at 15:21:16 UTC, Ellery Newcomer
wrote:
On 11/12/2013 06:38 AM, John Colvin wrote:
On Tuesday, 12 November 2013 at 13:50:49 UTC, Jacob Carlborg
wrote:
auto person = Person.where(e => e.name == "John");
Translates to:
select * from person where name = 'John'
for those of us entirely unfamiliar with linq, what is this
supposed to
do? Select people with name "John" from a collection of
people, like in
sql? It seems trivial to do this using filter, or am I missing
something...?
linq provides an interface to query any collection, but what is
interesting in this case is
Person.where(e => e.name == "John")
invokes an engine that builds the necessary sql to issue an
equivalent query to your sql database and assembles the results
into a range of Person. And it can do this for any arbitrary
predicate (well, almost. It doesn't handle function calls to
arbitrary code too well).
the .NET framework can do this because it exposes an api for
querying, building, and compiling asts.
D cannot do this because it doesn't. (and I have tried to make
it work)
oh, I see. Would AST macros really be enough to make this work in
D? "Arbitrary code" is a huge feature space in D, including much
that doesn't map well to anything outside of a relatively
low-level language, let alone SQL.
I can see it quickly becoming a nightmare that would be worse
than just issuing the predicate as an sql string or some generic
equivalent.
