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)
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Sys(3) OCaml library Sys(3) NAME
Sys - System interface. Module Module Sys Documentation Module Sys : sig end System interface. val argv : string array The command line arguments given to the process. The first element is the command name used to invoke the program. The following elements are the command-line arguments given to the program. val executable_name : string The name of the file containing the executable currently running. val file_exists : string -> bool Test if a file with the given name exists. val is_directory : string -> bool Returns true if the given name refers to a directory, false if it refers to another kind of file. Raise Sys_error if no file exists with the given name. Since 3.10.0 val remove : string -> unit Remove the given file name from the file system. val rename : string -> string -> unit Rename a file. The first argument is the old name and the second is the new name. If there is already another file under the new name, rename may replace it, or raise an exception, depending on your operating system. val getenv : string -> string Return the value associated to a variable in the process environment. Raise Not_found if the variable is unbound. val command : string -> int Execute the given shell command and return its exit code. val time : unit -> float Return the processor time, in seconds, used by the program since the beginning of execution. val chdir : string -> unit Change the current working directory of the process. val getcwd : unit -> string Return the current working directory of the process. val readdir : string -> string array Return the names of all files present in the given directory. Names denoting the current directory and the parent directory ( . and .. in Unix) are not returned. Each string in the result is a file name rather than a complete path. There is no guarantee that the name strings in the resulting array will appear in any specific order; they are not, in particular, guaranteed to appear in alphabetical order. val interactive : bool Pervasives.ref This reference is initially set to false in standalone programs and to true if the code is being executed under the interactive toplevel system ocaml . val os_type : string Operating system currently executing the OCaml program. One of - Unix (for all Unix versions, including Linux and Mac OS X), - Win32 (for MS-Windows, OCaml compiled with MSVC++ or Mingw), - Cygwin (for MS-Windows, OCaml compiled with Cygwin). val word_size : int Size of one word on the machine currently executing the OCaml program, in bits: 32 or 64. val big_endian : bool Whether the machine currently executing the Caml program is big-endian. Since 4.00.0 val max_string_length : int Maximum length of a string. val max_array_length : int Maximum length of a normal array. The maximum length of a float array is max_array_length/2 on 32-bit machines and max_array_length on 64-bit machines. === Signal handling === type signal_behavior = | Signal_default | Signal_ignore | Signal_handle of (int -> unit) (* What to do when receiving a signal: - Signal_default : take the default behavior (usually: abort the program) - Signal_ignore : ignore the signal - Signal_handle f : call function f , giving it the signal number as argument. *) val signal : int -> signal_behavior -> signal_behavior Set the behavior of the system on receipt of a given signal. The first argument is the signal number. Return the behavior previously associated with the signal. If the signal number is invalid (or not available on your system), an Invalid_argument exception is raised. val set_signal : int -> signal_behavior -> unit Same as Sys.signal but return value is ignored. === Signal numbers for the standard POSIX signals. === val sigabrt : int Abnormal termination val sigalrm : int Timeout val sigfpe : int Arithmetic exception val sighup : int Hangup on controlling terminal val sigill : int Invalid hardware instruction val sigint : int Interactive interrupt (ctrl-C) val sigkill : int Termination (cannot be ignored) val sigpipe : int Broken pipe val sigquit : int Interactive termination val sigsegv : int Invalid memory reference val sigterm : int Termination val sigusr1 : int Application-defined signal 1 val sigusr2 : int Application-defined signal 2 val sigchld : int Child process terminated val sigcont : int Continue val sigstop : int Stop val sigtstp : int Interactive stop val sigttin : int Terminal read from background process val sigttou : int Terminal write from background process val sigvtalrm : int Timeout in virtual time val sigprof : int Profiling interrupt exception Break Exception raised on interactive interrupt if Sys.catch_break is on. val catch_break : bool -> unit catch_break governs whether interactive interrupt (ctrl-C) terminates the program or raises the Break exception. Call catch_break true to enable raising Break , and catch_break false to let the system terminate the program on user interrupt. val ocaml_version : string ocaml_version is the version of OCaml. It is a string of the form major.minor[.patchlevel][+additional-info] , where major , minor , and patchlevel are integers, and additional-info is an arbitrary string. The [.patchlevel] and [+additional-info] parts may be absent. OCamldoc 2014-06-09 Sys(3)