Effect(3) OCaml library Effect(3)

# [NAME](#NAME)

Effect - Effects.

# [Module](#Module)

Module Effect

# [Documentation](#Documentation)

Module **Effect**  
: **sig end**

Effects.

See 'Language extensions/Effect handlers' section in the manual.

**Since** 5.0

**Alert unstable.** The Effect interface may change in incompatible ways in the future.

*type* **'a** *t* = **'a eff** = ..

The type of effects.

*exception Unhandled* **:** **'a t** **->** **exn**

**Unhandled e** is raised when effect **e** is performed and there is no handler for it.

*exception Continuation\_already\_resumed*

Exception raised when a continuation is continued or discontinued more than once.

*val perform* : **'a t -> 'a**

**perform e** performs an effect **e** .

**Raises Unhandled** if there is no handler for **e** .

*module Deep :* **sig end**

*module Shallow :* **sig end**

2026-10-01 OCamldoc

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Document: Effect(3o) from ocaml 5.5.1-r1 (Chainguard OS)
Source: https://github.com/ocaml/ocaml