Weak.S(3)

💅 NAME 💅

Okay bestie, quick vibe check: this is Weak.S, the output signature of the functor Weak.Make, and we're in the OCaml library / Weak.S(3) corner of the universe. That's the manual-name drop, folded in cute and not copy-pasted.

🦋 Module type 🦋

Module type Weak.S

Module type S = sig end

Literally an empty signature sig end — iconic minimalism, no cap.

💖 Documentation 💖

The output signature of the functor Weak.Make.

• type data — the type of the elements stored in the table. This is the thing your weak hash set is full of. 🍓
• type t — the type of tables that contain elements of type data. Big warning bestie: weak hash sets cannot be marshaled using output_value or the functions of the Marshal module. Not me finding that out the hard way 😭.

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• val create : int -> t — create n creates a new empty weak hash set, of initial size n. The table will grow as needed. Slay, it scales. ✨
• val clear : t -> unit — remove all elements from the table. Poof, empty, periodt.
• val merge : t -> data -> data — merge t x returns an instance of x found in t if any, or else adds x to t and return x. (The manual says “return”; we're keeping the lore exact.)
• val add : t -> data -> unit — add t x adds x to t. If there is already an instance of x in t, it is unspecified which one will be returned by subsequent calls to find and merge. So don't come for the ordering, it's giving unspecified 💀.
• val remove : t -> data -> unit — remove t x removes from t one instance of x. Does nothing if there is no instance of x in t. Lowkey polite.
• val find : t -> data -> data — find t x returns an instance of x found in t. Raises Not_found if there is no such element. The audacity of a missing element, honestly 🙈.
• val find_opt : t -> data -> data option — find_opt t x returns an instance of x found in t or None if there is no such element. Since 4.05. This one said “no thanks to exceptions” and we respect it. 🫶
• val find_all : t -> data -> data list — find_all t x returns a list of all the instances of x found in t. Collector energy.
• val mem : t -> data -> bool — mem t x returns true if there is at least one instance of x in t, false otherwise. Bool check, very demure.
• val iter : (data -> unit) -> t -> unit — iter f t calls f on each element of t, in some unspecified order. It is not specified what happens if f tries to change t itself. So don't mutate the table mid-iter, bestie; that's chaos main character energy and the manual is not promising you anything.
• val fold : (data -> 'acc -> 'acc) -> t -> 'acc -> 'acc — fold f t init computes (f d1 (... (f dN init))) where d1 ... dN are the elements of t in some unspecified order. It is not specified what happens if f tries to change t itself. Same warning, same unspecified vibe check.
• val count : t -> int — counts the number of elements in the table. count t gives the same result as fold (fun _ n -> n+1) t 0 but does not delay the deallocation of the dead elements. It's not just folding with extra steps; it has a deallocation glow-up. 🧚
• val stats : t -> int * int * int * int * int * int — returns statistics on the table. The numbers are, in order: table length, number of entries, sum of bucket lengths, smallest bucket length, median bucket length, biggest bucket length. Six ints, one tuple, fully blessed data. 🔥

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Catch you later, bestie — this page came from OCamldoc, dated 2026-06-22, for Weak.S(3) in the OCaml library. Stay weak-hash-set-pilled 💅✨