---
name: "Weak.S"
section: "3o"
platform: "linux"
package: "ocaml"
version: "5.5.0-1"
release: "Arch Linux 2026-11-01"
platforms: ["linux"]
url: "https://new.carta.tech/Weak.S"
---

# Weak.S(3o)

The output signature of the functor Weak.Make.

## NAME

Weak.S - The output signature of the functor Weak.Make.

## Module type

Module type   Weak.S

## Documentation

Module type **S**\
  \=  **sig end**

The output signature of the functor  **Weak.Make** .

*type data*

The type of the elements stored in the table.

*type t*

The type of tables that contain elements of type  **data** . Note that weak hash sets cannot be marshaled using **output\_value** or the functions of the  **Marshal** module.

*val create* :  **int -\> t**

**create n** creates a new empty weak hash set, of initial size  **n** .  The table will grow as needed.

*val clear* :  **t -\> unit**

Remove all elements from the table.

*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** .

*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** .

*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** .

*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.

*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

*val find\_all* :  **t -\> data -\> data list**

**find\_all t x** returns a list of all the instances of  **x** found in  **t** .

*val mem* :  **t -\> data -\> bool**

**mem t x** returns  **true** if there is at least one instance of  **x** in  **t** , false otherwise.

*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.

*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.

*val count* :  **t -\> int**

Count 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.

*val stats* :  **t -\> int \* int \* int \* int \* int \* int**

Return 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.