dynamic-import

Documentation

A dynamic import facility for CHICKEN Scheme.

Usage

(import dynamic-import)

Note strongly suggest warnings be disabled before using dynamic-import: (enable-warnings #f).

"Warning: imported identifier doesn't exist in module ..." can occur due to missing exported identifiers during module search. Also, warnings from dynamic-import flow thru a different channel.

dynamic-import

(dynamic-import (MD ...) (ID ...) [DEF])(dynamic-import MD ... (ID ...) [DEF])(dynamic-import (MD ...) ID ... [DEF])

Attempts to import the identifiers ID ... from a module, in the listed module MD ... order. Should no module succeed, the default specification DEF is used to bind the identifiers.

The extend module identifier syntax, ex: (srfi 1) & (main sub1 sub1-1), is supported. However, use does need to be as ((srfi 1) (main sub1 sub1-1)), to prevent misunderstanding.

MD ; (or symbol (list symbol fixnum) (list-of (or symbol number)))
ID ; (symbol)
DEF: (default * ...) ; literal default is (* ...)
DEF: procedure ; default is the result of (DEF IDs)

The IDs are assigned from the default list, w/ an element for each ID.

dynamic-import-warning

[parameter] (dynamic-import-warning [WARN]) -> procedure

: WARN ; (#!rest -> void) ; warning procedure; default warning

dynamic-importer

[procedure] (dynamic-importer MDS IDS [DEFAULT]) -> (or false list)

Performs runtime import.

MDS: see dynamic-import
IDS: see dynamic-import
DEFAULT: (or false list (import-names -> (or false list)))

Dynamic Plugin

Usage

(import dynamic-plugin)

import-plugin

[procedure] (import-plugin MDS IDS) -> (or false list)

Performs runtime import. Returns a list of the imports or #f.

Arguments MDS & IDS are like those of dynamic-importer but allow an atomic form.

import-plugin-option

[procedure] (import-plugin-option MDS IDS) -> (or false list)

Performs runtime import. Returns a list of the imports or #f.

Arguments MDS & IDS are like those of dynamic-importer but add string & allow an atomic form.

The addition of string is of dubious utility.

Examples

;;;; preferred list of TCP implementations
(import dynamic-import)

(parameterize ((enable-warnings #f) ;see note in documentation above
               (dynamic-import-warning void))
  ; tcp-listen ... from tcp6 else (chicken tcp) else stub
  ;
  ; default is procedure and called unlike the example below
  ;
    (dynamic-import (tcp6 (chicken tcp))
      (tcp-listen tcp-listener-fileno tcp-listener-port
       tcp-accept tcp-accept-ready? tcp-close
       tcp-abandon-port tcp-buffer-size tcp-connect
       tcp-read-timeout tcp-write-timeout)
      ; make, named, failure defaults for the imports
      (lambda (ids) (map (lambda (id) (lambda _ (error id "no dynamic import"))) ids)))
  ;
  ; NOTE on import failure: (tcp-read-timeout ...)
  ; => Error: (tcp-read-timeout) no such import

  ; ssl-connect* from openssl else stub
  ;
  ; default is literal, a procedure but not called as above.
  ;
  ; only one import so only one default; one per import.
  (dynamic-import openssl ssl-connect* (default (lambda _ (values #f #f))))
  ;
  ; NOTE on import failure: (ssl-connect* ...)
  ; => #f #f
)

Bugs & Limitations

Very not portable Scheme.
The toplevel is polluted due to lack of lexical scope.

Notes

Inspired by Feb 12 '22 #chicken irc discussion.

Requirements

Test dependencies only

test test-utils srfi-1

Author

Kon Lovett

Repository

This egg is hosted on the CHICKEN Subversion repository:

https://anonymous@code.call-cc.org/svn/chicken-eggs/release/5/dynamic-import

If you want to check out the source code repository of this egg and you are not familiar with Subversion, see this page.

Version history

1.6.0: Add import-plugin
1.5.1: Fix dynamic-plugin signature.
1.5.0: Add dynamic-plugin
1.4.2: Default #f valid.
1.4.1: Restrict import defaults.
1.4.1: Expose dynamic-importer.
1.3.0: CHICKEN 6 Release.

License

This code is in the public domain.