Metaprogramming without templates

[SealabJaster]

On Monday, 21 June 2021 at 13:18:21 UTC, Stefan Koch wrote:
> ...

Exciting, even if the end code looks like a complete hack!

Another thing: Entity Framework, when you give it something like:

```csharp
int age = 20; // Any external variable
MyDbContext.People.Where(person => person.Age >= age);
```

It's able to determine that `age` is an external variable, so 
essentially a parameter, and generates a prepared statement like:

```sql
SELECT * FROM people WHERE age >= $1;
```

And it will then automatically forward whatever's in `age` into 
parameter $1.

This is of course a very niche use-case, but it's one of the 
things that makes Entity Framework so fluent to use (i.e. your 
queries are written in normal C#, but are executed on the 
database instead of in the application's memory). Of course it 
falls back to client-side evaluation if it can't translate things.

This gets more complex the more conditions you tack on, as well 
as things like 
[.Include](https://docs.microsoft.com/en-us/ef/core/querying/related-data/eager).

This doesn't necessarily need the ability to rewrite the AST, but 
as you said, simply generate based off of the reflection of the 
AST.

And there's likely a lot more use cases outside of this example. 
But I'm now wondering what other things might be possible @_@