FunctoriaSourceFunctoria is a DSL to describe a set of modules and functors, their types and how to apply them in order to produce a complete application.
The main use case is mirage. See the Mirage documentation for details.
Functoria is a DSL to write configuration files for functor-heavy applications. Such configuration files (imaginatively called config.ml) usually contains three parts: one for defining toplevel modules, one for defining configuration kyes and one for defining applications using these modules and keys.
To define toplevel modules, use the main function. Among its various arguments, it takes the module name and its signature. The type is assembled with the Type combinators, like the @-> operator, which represents a functor arrow.
let main = main "Unikernel.Main" (m @-> job) This declares that the functor Unikernel.Main takes a module of type m and returns a module of type DSL.job. job has a specific meaning for functoria: it is a module which defines at least a function start, which should have one argument per functor argument and should return unit.
It is up to the user to ensure that the declaration matches the implementation, or be rewarded by a compiler error later on. If the declaration is correct, everything that follows will be.
A configuration key is composed of:
Consider a multilingual application: we want to pass the default language as a parameter. We will use a simple string, so we can use the predefined description Key.Arg.string. We want to be able to define it both at configure and run time, so we use the stage Both. This gives us the following code:
let lang_key =
let doc =
Key.Arg.info ~doc:"The default language for the application."
[ "l"; "lang" ]
in
Key.create "language" @@ Key.Arg.(opt ~stage:`Both string "en" doc)Here, we defined both a long option "--lang" and a short one "-l" (the format is similar to the one used by Cmdliner. In the application code, the value is retrieved with Key_gen.language ().
The option is also documented in the "--help" option for both the configure subcommand (at configure time) and ./app.exe (at startup time).
-l VAL, --lang=VAL (absent=en) The default language for the application.
To register a new application, use register:
let () = register "app" [ main $ impl ] This function (which should only be called once) takes as argument the name of the application and a list of jobs. The jobs are defined using the Impl DSL; for instance the operator $ is used to apply the functor main (aka Unikernel.Main) to the default console.
Once an application is registered, it can be configured and built using command-line arguments.
Configuration keys we can use be used to switch implementation at configure time. This is done by using the Key DSL, for instance to check whether lang_key is instanciated with a given string:
let lang_is "s" = Key.(pure (( = ) s) $ value lang_key) Then by using the if_impl combinator to choose between two implementations depending on the value of the key:
let impl = if_impl (is "fi") finnish_impl not_finnish_implementation The Functoria DSL allows users to describe how to create portable and flexible applications. It allows to pass application parameters easily using command-line arguments either at configure-time or at runtime.
include DSLConstruct a functor type from a type and an existing functor type. This corresponds to prepending a parameter to the list of functor parameters. For example:
kv_ro @-> ip @-> kv_ro This describes a functor type that accepts two arguments -- a kv_ro and an ip device -- and returns a kv_ro.
Same as impl but with hidden type.
dep t is the (build-time) dependency towards t.
The type for keys' parsing context. See Key.context.
if_impl v impl1 impl2 is impl1 if v is resolved to true and impl2 otherwise.
match_impl v cases ~default chooses the implementation amongst cases by matching the v's value. default is chosen if no value matches.
For specifying opam package dependencies, the type package is used. It consists of the opam package name, the ocamlfind names, and optional lower and upper bounds. The version constraints are merged with other modules.
Installation scope of a package.
val package :
?scope:scope ->
?build:bool ->
?sublibs:string list ->
?libs:string list ->
?min:string ->
?max:string ->
?pin:string ->
?pin_version:string ->
string ->
packageSame as Functoria.Package.v
Values of type impl are tied to concrete module implementation with the device and foreign construct. Module implementations of type job can then be registered into an application builder. The builder is in charge if parsing the command-line arguments and of generating code for the final application. See Functoria.Lib for details.
val foreign :
?packages:package list ->
?packages_v:package list value ->
?keys:abstract_key list ->
?deps:abstract_impl list ->
string ->
'a typ ->
'a implAlias for main, where ?extra_deps has been renamed to ?deps.
val main :
?packages:package list ->
?packages_v:package list value ->
?keys:abstract_key list ->
?extra_deps:abstract_impl list ->
string ->
'a typ ->
'a implforeign name typ is the functor name, having the module type typ. The connect code will call <name>.start.
packages or packages_v is set, then the given packages are installed before compiling the current application.keys is set, use the given keys to parse at configure and runtime the command-line arguments before calling <name>.connect.extra_deps is set, the given list of abstract implementations is added as data-dependencies: they will be initialized before calling <name>.connect.val impl :
?packages:package list ->
?packages_v:package list Key.value ->
?install:(Info.t -> Install.t) ->
?install_v:(Info.t -> Install.t Key.value) ->
?keys:Key.t list ->
?extra_deps:abstract_impl list ->
?connect:(info -> string -> string list -> string) ->
?dune:(info -> Dune.stanza list) ->
?configure:(info -> unit Action.t) ->
?files:(info -> Fpath.t list) ->
string ->
'a typ ->
'a implimpl ... is of_device @@ Device.v ...
module type KEY =
module type of Key
with type 'a Arg.converter = 'a Key.Arg.converter
and type 'a Arg.t = 'a Key.Arg.t
and type Arg.info = Key.Arg.info
and type 'a value = 'a Key.value
and type 'a key = 'a Key.key
and type t = Key.t
and type Set.t = Key.Set.t
and type 'a Alias.t = 'a Key.Alias.t
and type context = Key.contextThe signature for run-time and configure-time command-line keys.
Signature for functoria devices. A device is a module implementation which contains a runtime state which can be set either at configuration time (by the application builder) or at runtime, using command-line arguments.
noop is an implementation of job that holds no state, does nothing and has no dependency.
The type for command-line arguments, similar to the usual Sys.argv.
sys_argv is a device providing command-line arguments by using Sys.argv.
keys a is an implementation of job that holds the parsed command-line arguments. By default runtime_package is "functoria-runtime" and runtime_modname is "Functoria_runtime".
val app_info :
?runtime_package:string ->
?build_info:(string * string) list ->
?gen_modname:string ->
?modname:string ->
unit ->
info implapp_info is the module implementation whose state contains all the information available at configure-time.
gen_modname: if not set, it is Info_gen.modname is the name of the runtime module defining values of type info. By default it's Functoria_runtime.Application builder. API for building libraries to link with config.ml
The Functoria DSL allows users to describe how to create portable and flexible applications. It allows to pass application parameters easily using command-line arguments either at configure-time or at runtime.