Operations on references.
References are mutable values, i.e. "variables" which may actually change value during their life-time, as variables in imperative languages. References can be understood as 1-cell arrays and are typically used to implement imperative algorithms in OCaml.
References are useful but don't abuse them.
Return a fresh reference containing the given value.
!r returns the current contents of reference r. Equivalent to fun r -> r.contents.
val (:=) : 'a ref -> 'a -> r := a stores the value of a in reference r. Equivalent to fun r v -> r.contents <- v.
val set : 'a ref -> 'a -> copy r returns a new reference with the same initial content as r.
val pre : 'a ref -> ('a -> 'a ) -> 'a Perform an operation on a reference and return the new value of that reference.
For instance, if x is a reference to 1, pre x ( ( + ) 1) returns 2 and sets x to 2.
val post : 'a ref -> ('a -> 'a ) -> 'a Perform an operation on a reference and return the previous value of that reference.
For instance, if x is a reference to 1, post x ( ( + ) 1) returns 1 and sets x to 2.
val swap : 'a ref -> 'a ref -> swap a b puts !b in a and !a in b
val post_incr : int ref -> Increment an integer, return the old value.
Comparable to C or Java's i++.
val post_decr : int ref -> Decrement an integer, return the old value.
Comparable to C or Java 's i--.
val pre_incr : int ref -> Increment an integer, return the new value.
Comparable to C or Java's ++i.
val pre_decr : int ref -> Increment an integer, return the new value.
Comparable to C or Java's --i.
val protect : 'a ref -> 'a -> (unit -> 'b ) -> 'b Assign a reference temporarily.
protect r v body sets the value of r to v and executes body. Once body has been executed, whether termination happens as a consequence of regular evaluation or exception, the previous value of r is restored.
val toggle : bool ref -> Invert the boolean stored in the reference
val oset : 'a optionref -> 'a -> Set the given option ref to Some x
val oget_exn : 'a optionref -> 'a Get a value from an option ref;
Given a printing function for the value in the ref, produce a printing function for the ref.
Example: IO.to_string (Ref.print Int.print) (ref 20) = "20"
Given a comparison function, produce a comparison function for refs of that type.
Example: let a = ref 10 and b = ref 20 in Ref.compare Int.compare a b = -1
Given an ordering function, produce an ordering function for refs of that type.
Example: let a = ref 10 and b = ref 20 in Ref.ord Int.ord a b = Ord.Lt