package algaeff

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Signatures of read effects.

type env

The type of environments.

val read : unit -> env

Read the environment.

val scope : (env -> env) -> (unit -> 'a) -> 'a

scope f t runs the thunk t under the new environment that is the result of applying f to the current environment.

val run : env:env -> (unit -> 'a) -> 'a

run ~env t runs the thunk t which may perform reading effects on the value env.

val register_printer : ([ `Read ] -> string option) -> unit

register_printer p registers a printer p via Printexc.register_printer to convert the unhandled internal effect into a string for the OCaml runtime system to display. Ideally, the internal effect should have been handled by run and there is no need to use this function, but when it is not the case, this function can be helpful for debugging. The functor Reader.Make always registers a simple printer to suggest using run, but you can register new ones to override it. The return type of the printer p should return Some s where s is the resulting string, or None if it chooses not to convert a particular effect. The registered printers are tried in reverse order until one of them returns Some s for some s; that is, the last registered printer is tried first. Note that this function is a wrapper of Printexc.register_printer and all the registered printers (via this function or Printexc.register_printer) are put into the same list.

The input type of the printer p is a variant representation of the only internal effect used in this module. It corresponds to the effect trigger by read.

  • since 1.1.0

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