[bitc-dev] on mutable types

[Swaroop Sridhar]

Sam Mason wrote:
> It's probably a bit late for this, but I'm a bit confused by the "mutable"
> keyword.  It appears to do two things, firstly it allows the contents
> of a variable to be changed at runtime.  Secondly, in providing this
> mutability an extra level of indirection is introduced -- it is this that
> surprises me.  

No extra level of indirection is introduced. The mutable keyword 
qualifies the type of an expression, allowing it to be mutated. There is 
no `mutable' value constructor.

ex:

(define x:(mutable int32) 10)
(define y:int32 10)

Both x and y have the same representation. x is mutable, y is immutable.

Swaroop.