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static-modules

static-modules

Description

static-modules is a Scheme implementation of the module system described by Xavier Leroy in the paper A Modular Module System.

Library Procedures

Identifiers

[procedure] (ident? X) -> BOOL

Returns #t if X is an identifier, #f otherwise.

[procedure] (ident-name IDENT) -> STRING

Returns the string name associated with the given identifier.

[procedure] (ident-stamp IDENT) -> INT

Returns the unique stamp of the given identifier.

[procedure] (ident-create NAME) -> IDENT

Returns a fresh identifier associated with the given name.

[procedure] (ident-equal? IDENT IDENT) -> BOOL

Returns #t if the stamps of the given identifiers are equal, #f otherwise.

[procedure] (ident-empty) -> IDENV

Returns an empty identifier environment.

[procedure] (ident-add IDENT DATA IDENV) -> IDENV

Adds the given identifier and associated data to the given identifier environment.

[procedure] (ident-find IDENT IDENV) -> DATA

Looks up the given identifier in the given identifier environment and returns the associated data, or #f if not found.

We refer to named types, values (variables), and modules either by identifier (if we are in the scope of their binding) or via the dot notation, e.g. M.x to refer to component x of module M. Access paths represent both kinds of references.

[procedure] (path? X) -> BOOL

Returns #t if X is an access path, #f otherwise.

[procedure] (Pident IDENT) -> PATH

Returns a path consisting of the given identifier.

[procedure] (Pdot PATH STRING) -> PATH

Returns an access path for the given path and field.

[procedure] (path-equal? PATH PATH) -> BOOL

Returns #t if the two given paths are equal, #f otherwise.

Substitutions

[procedure] (subst-add IDENT PATH IDENV) -> IDENV

Extends the substition environment with the given identifier and path.

[procedure] (subst-path PATH IDENV) -> PATH

Applies the given substitutions to the given path.

[procedure] (subst-identity) -> IDENV

Returns an empty substitution environment.

Abstract syntax for the base language

[procedure] (make-core-syntax term? valtype? deftype? kind? make-valtype make-deftype subst-valtype subst-deftype subst-kind)

This procedure creates the structure describing base language syntax. The meaning of the fields is as follows:

term?: predicate for value expressions
valtype?: predicate for type expressions
deftype?: predicate for type definitions
kind?: predicate for the kinds that a type definition can have
make-valtype: constructor for type expressions
make-deftype: constructor for type definitions
subst-valtype: substitution function for type expressions
subst-deftype: substitution function for type definitions
subst-kind: substitution function for kinds

Abstract syntax for the module language

[procedure] (make-mod-syntax core)

This procedure creates the structure describing module language syntax. core is an object created by make-core-syntax. This procedure returns multiple values with the following meaning:

modtype? Signature Functorty: predicate and constructors for module type definitions
modspec? Value_sig Type_sig Module_sig: predicate and constructors for module type expressions
modterm? Modid Structure Functor Mapply Constraint: module term constructors
moddef? Value_def Type_def Module_def: predicate and constructor for module definitions
subst-modtype subst-modspec subst-typedecl: substitution procedures

Type-checking the base language

[procedure] (make-core-typing type-term kind-deftype check-valtype check-kind valtype-match deftype-equiv kind-match deftype-of-path)

This procedure creates the structure describing base language type checking. The meaning of the fields is as follows:

type-term: the main typing function, which takes a type and an environment, and returns the principal type of the term in the given environment
kind-deftype: infers and returns the kind of the given definable type
check-valtype check-kind: check the well-formedness of type and kind expressions in the base language
valtype-match deftype-equiv kind-match: checking values vs. signatures
deftype-of-path: transforms a type path and its kind into the corresponding definable type

Type-checking the module language

[procedure] (make-mod-typing core-syntax core-typing)

This procedure creates the structure describing module language type checking. core-syntax is an object created by make-core-syntax, and core-typing is an object created by make-core-typing. This procedure returns multiple values with the following meaning:

check-modtype: checks the well-formedness of a module type
check-signature: checks the well-formedness of a signature
type-modterm: infers and returns the type of a module term
type-moddef: infers and returns the type of a module definition (sequence of definitions)
type-definition: infers and returns the type of a definition (inside a module or at toplevel)

Scoping

This library implements generic scoping pass for the module language. This pass is not described in the paper.

Scoping is the act of associating identifiers with their binding location. We assume that the parser generates fresh identifiers each time it encounters an occurrence of a lexical identifier in the program, and stores those fresh identifiers in the abstract syntax tree it constructs. The scoping pass rewrites the abstract syntax tree to use identical identifiers at a binding site and at all its usage sites.

[procedure] st-empty

Empty scoping table.

[procedure] (st-enter-value ID SC) -> SC

Enters a value identifier in the given scoping table.

[procedure] (st-enter-type ID SC) -> SC

Enters a type identifier in the given scoping table.

[procedure] (st-enter-module ID SC) -> SC

Enters a module identifier in the given scoping table.

[procedure] (st-value-path PATH SC) -> PATH
[procedure] (st-type-path PATH SC) -> PATH
[procedure] (st-module-path PATH SC) -> PATH
[procedure] (st-scope-module PATH SC) -> PATH

Evaluation

[procedure] (make-mod-eval core-syntax core-eval enter-val)

This procedure creates the structure describing module language type checking. core-syntax is an object created by make-core-syntax, and core-eval is a procedure to evalue core syntactic terms. This procedure returns multiple values with the following meaning:

modval?: predicate for module values
Structure_v: constructor for a structure of values
Mclosure_v: constructor for a structure closure
path-find-val: given a path and value environment, returns the corresponding value, if it exists in the environment
find-module-val: like path-find-val, but only for modules
mod-eval: given an evaluation environment and a list of module definitions, evaluates and returns the corresponding value

Version History

1.7 Added record printer for moddef datatype
1.4 Bug fix in evaluation of constraint terms
1.3 Bug fix in signature checking
1.2 Changed make-mod-eval interface to be consistent with the rest of the procedures [thanks to Peter Bex]
1.1 Removed exports of internally-defined modtype data constructors [thanks to Peter Bex]
1.0 Initial Release

License

static-modules is based on the code and paper by Xavier Leroy (2000): A modular module system. Journal of Functional Programming, 10, pp 269-303

Copyright 2010-2013 Ivan Raikov and the Okinawa Institute of
Science and Technology.

This program is free software: you can redistribute it and/or
modify it under the terms of the GNU General Public License as
published by the Free Software Foundation, either version 3 of the
License, or (at your option) any later version.

This program is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
General Public License for more details.

A full copy of the GPL license can be found at
<http://www.gnu.org/licenses/>.