[rvba]

> In herd, everything is immutable unless declared with var

So basucally everything is var?

[jcparkyn]

I'm not sure if I understand the question?

There are two ways to define a variable binding:

    x = 1; // declares x as immutable
    var y = 2; // declares y as mutable

The "default" behaviour (if no keyword is used) is to define a new immutable variable.

[rvba]

I'm asking if the reality wouldn't be that "everything" is set as mutable by default and the non mutable part is ignored.