lazy(3o) [debian man page]

Lazy(3o)							   OCaml library							  Lazy(3o)

NAME

       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 definitions 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	-rectypes  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 with-
       out recomputing it. If it raised an exception, the same exception is raised again.  Raise 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 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 Undefined .

       val lazy_from_fun : (unit -> 'a) -> 'a t

       lazy_from_fun f is the same as lazy (f ()) but slightly more efficient.

       val lazy_from_val : 'a -> 'a t

       lazy_from_val v returns an already-forced suspension of v This is for special purposes only and should not be confused with lazy (v) .

       val lazy_is_val : 'a t -> bool

       lazy_is_val x returns true if x has already been forced and did not raise an exception.

OCamldoc							    2012-06-26								  Lazy(3o)

Printexc(3o)							   OCaml library						      Printexc(3o)

NAME

       Printexc - Facilities for printing exceptions.

Module
       Module	Printexc

Documentation
       Module Printexc
	: sig end

       Facilities for printing exceptions.

       val to_string : exn -> string

       Printexc.to_string e returns a string representation of the exception e .

       val print : ('a -> 'b) -> 'a -> 'b

       Printexc.print  fn  x applies fn to x and returns the result.  If the evaluation of fn x raises any exception, the name of the exception is
       printed on standard error output, and the exception is raised again.  The typical use is to catch and report exceptions that escape a func-
       tion application.

       val catch : ('a -> 'b) -> 'a -> 'b

       Printexc.catch  fn  x  is  similar to Printexc.print , but aborts the program with exit code 2 after printing the uncaught exception.  This
       function is deprecated: the runtime system is now able to print uncaught exceptions as precisely as Printexc.catch does.  Moreover, calling
       Printexc.catch  makes  it harder to track the location of the exception using the debugger or the stack backtrace facility.  So, do not use
       Printexc.catch in new code.

       val print_backtrace : Pervasives.out_channel -> unit

       Printexc.print_backtrace oc prints an exception backtrace on the output channel oc .  The backtrace lists the program locations	where  the
       most-recently raised exception was raised and where it was propagated through function calls.

       Since 3.11.0

       val get_backtrace : unit -> string

       Printexc.get_backtrace () returns a string containing the same exception backtrace that Printexc.print_backtrace would print.

       Since 3.11.0

       val record_backtrace : bool -> unit

       Printexc.record_backtrace  b  turns  recording of exception backtraces on (if b = true ) or off (if b = false ).  Initially, backtraces are
       not recorded, unless the b flag is given to the program through the OCAMLRUNPARAM variable.

       Since 3.11.0

       val backtrace_status : unit -> bool

       Printexc.backtrace_status() returns true if exception backtraces are currently recorded, false if not.

       Since 3.11.0

       val register_printer : (exn -> string option) -> unit

       Printexc.register_printer fn registers fn as an exception printer.  The printer should return None or raise an exception  if  it  does  not
       know  how to convert the passed exception, and Some s with s the resulting string if it can convert the passed exception. Exceptions raised
       by the printer are ignored.

       When converting an exception into a string, the printers will be invoked in the reverse order  of  their  registrations,  until	a  printer
       returns a Some s value (if no such printer exists, the runtime will use a generic printer).

       Since 3.11.2

OCamldoc							    2012-06-26							      Printexc(3o)