String lambdas

[Andrei Alexandrescu via Digitalmars-d]

https://github.com/dlang/phobos/pull/3882

I just closed with some regret a nice piece of engineering. Please 
comment if you think string lambdas have a lot of unexploited potential.

One thing we really need in order to 100% replace string lambdas with 
lambdas is function equivalence. Right now we're in the odd situation 
that SomeTemplate!((a, b) => a < b) has distinct types, one per 
instantiation.


Andrei