type tlet g,h = Weak_glass.create is analogous to
let g = Glass.create () and h = watch g except it also lets you see when it's
unwatched. It is a guarantee that after unwatched g becomes determined,
break g will no longer have any effect (because the user has lost all references
to all hearts derived from h).
let g,h = Weak_glass.create is analogous to
let g = Glass.create () and h = watch g except it also lets you see when it's
unwatched. It is a guarantee that after unwatched g becomes determined,
break g will no longer have any effect (because the user has lost all references
to all hearts derived from h).