# Structure Meta

Identifier index | Structure index
--- | ---

    (* Meta -- functions available only in interactive Moscow ML sessions *)

    val printVal         : 'a -> 'a
    val printDepth       : int ref
    val printLength      : int ref
    val installPP        : (ppstream -> 'a -> unit) -> unit

    val liberal          : unit -> unit
    val conservative     : unit -> unit
    val orthodox         : unit -> unit

    val use              : string -> unit
    val compile          : string -> unit
    val compileToplevel  : string list -> string -> unit
    val compileStructure : string list -> string -> unit

    val load             : string -> unit
    val loadOne          : string -> unit
    val loaded           : unit -> string list
    val loadPath         : string list ref

    val quietdec         : bool ref
    val verbose          : bool ref

    val quotation        : bool ref
    val valuepoly        : bool ref

    val quit             : unit -> 'a

    (*
       These values and functions are available in the Moscow ML
       interactive system only.

       [printVal e] prints the value of expression e to standard output
       exactly as it would be printed at top-level, and returns the value
       of e.  Output is flushed immediately.  This function is provided as
       a simple debugging aid.  The effect of printVal is similar to that
       of `print' in Edinburgh ML or Umeaa ML.  For string arguments, the
       effect of SML/NJ print can be achieved by the function
       TextIO.print : string -> unit.

       [printDepth] determines the depth (in terms of nested constructors,
       records, tuples, lists, and vectors) to which values are printed by
       the top-level value printer and the function printVal.  The components
       of the value whose depth is greater than printDepth are printed as
       `#'.  The initial value of printDepth is 20. This value can be
       changed at any moment, by evaluating, for example,
            printDepth := 17;

       [printLength] determines the way in which list values are printed
       by the top-level value printer and the function printVal.  If the
       length of a list is greater than printLength, then only the first
       printLength elements are printed, and the remaining elements are
       printed as `...'.  The initial value of printLength is 200.  This
       value can be changed at any moment, by evaluating, for example,
            printLength := 500;

       [quit ()] quits Moscow ML immediately.

       [installPP pp] installs the prettyprinter pp : ppstream -> ty -> unit
       at type ty.  The type ty must be a nullary (parameter-less) type
       constructor representing a datatype, either built-in (such as bool)
       or user-defined.  Whenever a value of type ty is about to be
       printed by the interactive system, or function printVal is invoked
       on an argument of type ty, the pretty-printer pp will be invoked to
       print it.  See library unit PP for more information.

       [use "f"] causes ML declarations to be read from file f as if they
       were entered from the console.  A file loaded by use may, in turn,
       evaluate calls to use.  For best results, use `use' only at top
       level, or at top level within a use'd file.

       [liberal ()] sets liberal mode for the compilation functions:
       accept (without warnings) all extensions to the SML Modules
       language.  The extensions are: higher-order modules (functors
       defined within structures and functors); first-order modules
       (structures can be packed as values, and values can be unpacked as
       structures); and recursively defined modules (signatures and
       structures). The liberal, conservative, and orthodox modes affect
       the functions compile, compileStructure, and compileToplevel.  The
       liberal mode may be set also by the mosml option -liberal.

       [conservative ()] sets conservative mode for the compilation
       functions: accept all extensions to the SML Modules language, but
       issue a warning for each use.  The conservative mode may be set
       also by the mosml option -conservative.  This is the default.

       [orthodox ()] sets orthodox mode for the compilation functions:
       reject all uses of the extensions to the SML Modules language.
       That is, accept only SML Modules syntax.  The orthodox mode may be
       set also by the mosml option -orthodox.

       [compile "U.sig"] will compile and elaborate the specifications in
       file U.sig in structure mode, producing a compiled signature U in
       file U.ui.  This function is backwards compatible with Moscow ML
       1.44 and earlier.  Equivalent to compileStructure [] "U.sig".

       [compile "U.sml"] will elaborate and compile the declarations in
       file U.sml in structure mode, producing a compiled structure U in
       bytecode file U.uo.  If there is an explicit signature file U.sig,
       then file U.ui must exist, and the unit body must match the
       signature.  If there is no U.sig, then an inferred signature file
       U.ui will be produced also.  No evaluation takes place.  This
       function is backwards compatible with Moscow ML 1.44 and earlier.
       Equivalent to compileStructure [] "U.sml".

       The declared identifiers will be reported if verbose is true (see
       below); otherwise compilation will be silent.  In any case,
       compilation warnings are reported, and compilation errors abort the
       compilation and raise the exception Fail with a string argument.

       [compileStructure opnunits "U.sig"] compiles the specifications
       in file U.sig as if they form a signature declaration
            signature U = sig ... contents of U.sig ... end
       The contents of opnunits is added to the compilation context in
       which the specifications in U.sig are compiled.  The result is a
       compiled signature file U.ui.  This
       corresponds to invoking the batch compiler as follows:
            mosmlc -c U1.ui ... Un.ui -structure U.sig
       where opnunits equals ["U1", ..., "Un"].

       [compileStructure opnunits "U.sml"] compiles the declarations in
       file U.sml as if they formed a structure declaration
            structure U = struct ... contents of U.sml ... end
       The contents of opnunits is added to the compilation context in
       which the declarations in U.sml are compiled.  If U.ui exists
       already and represents a signature called U, then the compiled
       declarations are matched against it.  The result is a bytecode file
       U.uo.  If no file U.ui existed, then also a file U.ui is created,
       containing the inferred signature of structure U.  This
       corresponds to invoking the batch compiler as follows:
            mosmlc -c U1.ui ... Un.ui -structure U.sml
       where opnunits equals ["U1", ..., "Un"].

       [compileToplevel opnunits "U.sig"] compiles the specifications in
       file U.sig, in a context in which all declarations from opnunits
       are visible, creating a compiled signature file U.ui.  This
       corresponds to invoking the batch compiler as follows:
            mosmlc -c U1.ui ... Un.ui -toplevel U.sig
       where opnunits equals ["U1", ..., "Un"].

       [compileToplevel opnunits "U.sml"] compiles the declarations in
       file U.sml, in a context in which all declarations from opnunits
       are visible, creating a bytecode file U.uo.  If U.ui exists
       already, then the compiled declarations are matched against it;
       otherwise the file U.ui is created.  This corresponds to invoking the
       batch compiler as follows
            mosmlc -c U1.ui ... Un.ui -toplevel U.sml
       where opnunits equals ["U1", ..., "Un"].

       [load "U"] will load and evaluate the compiled unit body from file
       U.uo.  The resulting values are not reported, but exceptions are
       reported, and cause evaluation and loading to stop.  If U is
       already loaded, then load "U" has no effect.  If any other unit is
       mentioned by U but not yet loaded, then it will be loaded
       automatically before U.

       After loading a unit, it can be opened with `open U'.  Opening it
       at top-level will list the identifiers declared in the unit.

       When loading U, it is checked that the signatures of units
       mentioned by U agree with the signatures used when compiling U, and
       it is checked that the signature of U has not been modified since U
       was compiled; these checks are necessary for type safety.  The
       exception Fail is raised if these signature checks fail, or if the
       file containing U or a unit mentioned by U does not exist.

       [loadOne "U"] is similar to `load "U"', but raises exception Fail
       if U is already loaded or if some unit mentioned by U is not yet
       loaded.  That is, it does not automatically load any units
       mentioned by U.  It performs the same signature checks as `load'.

       [loaded ()] returns a list of the names of all compiled units that
       have been loaded so far.  The names appear in some random order.

       [loadPath] determines the load path: which directories will be
       searched for interface files (.ui files), bytecode files (.uo
       files), and source files (.sml files).  This variable affects the
       load, loadOne, and use functions.  The current directory is always
       searched first, followed by the directories in loadPath, in order.
       By default, only the standard library directory is in the list, but
       if additional directories are specified using option -I, then these
       directories are prepended to loadPath.

       [quietdec] when true, turns off the interactive system's prompt and
       responses, except warnings and error messages.  Useful for writing
       scripts in SML.  The default value is false; can be set to true
       with the -quietdec command line option.

       [verbose] determines whether the signature inferred by a call to
       compile will be printed.  The printed signature follows the syntax
       of Moscow ML signatures, so the output of compile "U.sml" can be
       edited to subsequently create file U.sig.  The default value is
       ref false.

       [quotation] determines whether quotations and antiquotations are
       permitted in declarations entered at top-level and in files
       compiled with compile.  A quotation is a piece of text surrounded
       by backquote characters `a b c` and is used to embed object
       language phrases in ML programs; see the Moscow ML Owner's Manual
       for a brief explanation of quotations.  When quotation is false,
       the backquote character is an ordinary symbol which can be used in
       ML symbolic identifiers.  When quotation is true, the backquote
       character is illegal in symbolic identifiers, and a quotation `a b
       c` will be recognized by the parser and evaluated to an object of
       type 'a General.frag list.  False by default.

       [valuepoly] determines whether value polymorphism is used or not in
       the type checker.  With value polymorphism (the default), there is
       no distinction between imperative ('_a) and applicative ('a) type
       variables, and type variables are generalized only in bindings to
       non-expansive expressions.  Non-generalized type variables are left
       free, to be instantiated when the bound identifier is used.  An
       expression is non-expansive if it is a variable, a special
       constant, a function, a tuple or record of non-expansive
       expressions, a parenthesized or typed non-expansive expression, or
       the application of an exception or value constructor (other than
       ref) to a non-expansive expression.  If valuepoly is false, then
       the type checker will distinguish imperative and applicative type
       variables, generalize all applicative type variables, and
       generalize imperative type variables only in non-expansive
       expressions.  True by default.
    *)

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Moscow ML 2.00