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val sexp_of_t :
('a -> Ppx_sexp_conv_lib.Sexp.t) ->
'a t ->
Ppx_sexp_conv_lib.Sexp.t
val create : ?use_current_scope:bool -> 'a -> 'a t
By default, a variable is created in Scope.top
, on the theory that its value depends on external stimuli (via Var.set
), not on the current scope. However, in some situations it is useful to supply ~use_current_scope:true
to create a variable that is invalidated when the current scope is invalidated, e.g. if one wants to use on_update (watch var) ~f:(function Invalidated -> ... | ...)
to remove the external stimulus that was setting var
.
It is allowed to do let t = create a
during stabilization; for that stabilization, watch t
will have value a
.
val set : 'a t -> 'a -> unit
set t a
sets the value of t
to a
. Outside of stabilization, subsequent calls to Var.value t
will see a
, but the set
will not have any effect on incrementals until the next stabilization, at which point watch t
will take on whatever value t
was at the start of stabilization, causing incremental recomputation as usual.
During a stabilization, calling set
will behave as if set
was called after stabilization finished: the new value will not be seen (by value v
or watch v
) until after the stabilization finishes.
val watch : 'a t -> 'a incremental
watch t
returns an incremental that tracks the value of t
. For a given t
, all calls to watch t
return the same incremental.
val value : 'a t -> 'a
value t
returns the value most recently set
for t
outside of stabilization.
val latest_value : 'a t -> 'a
latest_value t
returns the value most recently set
for t
. It can differ from value t
only during stabilization.