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LAZY(3O) - Linux man page online | Library functions

Deferred computations.

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Lazy - Deferred computations. Module Module Lazy Documentation Module Lazy : sig end Deferred computations. type 'a t = 'a lazy_t A value of type 'a Lazy.t is a deferred computation, called a suspension, that has a result of type 'a . The special expression syntax lazy (expr) makes a suspension of the computation of expr , without computing expr itself yet. "Forcing" the suspension will then compute expr and return its result. Note: lazy_t is the built-in type constructor used by the compiler for the lazy keyword. You should not use it directly. Always use Lazy.t instead. Note: Lazy.force is not thread-safe. If you use this module in a multi-threaded program, you will need to add some locks. Note: if the program is compiled with the -rectypes option, ill-founded recursive defini‐ tions of the form let rec x = lazy x or let rec x = lazy(lazy(...(lazy x))) are accepted by the type-checker and lead, when forced, to ill-formed values that trigger infinite loops in the garbage collector and other parts of the run-time system. Without the -rec‐ types option, such ill-founded recursive definitions are rejected by the type-checker. exception Undefined val force : 'a t -> 'a force x forces the suspension x and returns its result. If x has already been forced, Lazy.force x returns the same value again without recomputing it. If it raised an excep‐ tion, the same exception is raised again. Raise Lazy.Undefined if the forcing of x tries to force x itself recursively. val force_val : 'a t -> 'a force_val x forces the suspension x and returns its result. If x has already been forced, force_val x returns the same value again without recomputing it. Raise Lazy.Undefined if the forcing of x tries to force x itself recursively. If the computation of x raises an exception, it is unspecified whether force_val x raises the same exception or Lazy.Unde‐ fined . val from_fun : (unit -> 'a) -> 'a t from_fun f is the same as lazy (f ()) but slightly more efficient. from_fun should only be used if the function f is already defined. In particular it is always less efficient to write from_fun (fun () -> expr) than lazy expr . Since 4.00.0 val from_val : 'a -> 'a t from_val v returns an already-forced suspension of v . This is for special purposes only and should not be confused with lazy (v) . Since 4.00.0 val is_val : 'a t -> bool is_val x returns true if x has already been forced and did not raise an exception. Since 4.00.0 val lazy_from_fun : (unit -> 'a) -> 'a t Deprecated. synonym for from_fun . val lazy_from_val : 'a -> 'a t Deprecated. synonym for from_val . val lazy_is_val : 'a t -> bool Deprecated. synonym for is_val .
2017-10-20 source: Lazy(3o)
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