tfeb-lisp-tools

TFEB.ORG Lisp tools

This repo contains a system which will be a collection of fairly miscellaneous Common Lisp tools, which I have written over the years in order to generally get stuff done. Currently only two are published here:

I hope to add more tools as I disentangle them from the things they’re currently entangled with and modernise them where needed. All of the tools are intended to be portable CL except where documented.

The descriptions here are at best partial1.

General

Portability

These tools purport to be portable Common Lisp. If they’re not that’s either a bug in the tools or a bug in the CL implementation. In the former case I very definitely want to know, and I am also willing to add workarounds for the latter although I may be unable to test them on implementations I don’t use.

Zero history

All of these tools have long and varied histories. However these histories are entangled with a lot of other code which is not public, so that history is not represented in the publication repo where you are probably reading this.

Naming conventions

All of these tools make use of, and often work best with, domain-structured names: packages, modules, features and so on have names which start with a DNS domain name in reverse order and then may continue to divide further. In this case the prefix is org.tfeb.tools: org.tfeb is the DNS component and tools is the division within the DNS part.

This naming convention ensures uniqueness of things like package names. It does make typing package-qualified names somewhat irritating: the solution is not to do that but to construct packages which import or use the symbols you need. CL’s default package system is very well up to solving this problem, rumours to the contrary notwithstanding: conduit packages can make it a little simpler to express what you want to do.

Nothing actually cares that names correspond to real DNS domains: some things do care that the namespace is hierarchically structured and big-endian.


Requiring modules with searching: require-module

Although CL now has competent tools for defining and distributing ‘systems’ of code, in the form of ASDF and particularly Quicklisp, not all bits of code are large enough to justify their use. In particular it’s in the nature of the incremental and exploratory programming style encouraged by CL that people2 tend to write a bunch of little tools and utilities, living in single source files, which help them get their work done and which they reuse over time. Some of these may be portable, some not, and many of them can be quite small: a tool I use very often is under 50 lines excluding noise, but including docstrings and comments, and I have had smaller ones.

Turning these small tools into ASDF systems3 either means combining them into some larger conglomeration of code such as this one, or doubling the number of files you have to deal with because of the system definition files for each small tool. Combining them into a larger conglomeration of code means everything takes longer and costs more; doubling the number of files means the same. Also, of course, the ancestor of require-module predates the common availability of portable system definition tools by many years.

Well, CL has require, provide and *modules* and although these are deprecated, they’re not going away any time soon, or in fact ever. So a reasonable approach is to make all the small tools into modules by adding suitable provide incantations, and then to use require to load them. This still leaves the problem that require needs to know where to find the module being required is in the filesystem, and I didn’t want to fill code with explicit pathnames, even though logical pathnames make things at least a little better.

require-module provides a variant of require which has a portable mechanism for searching for and locating files corresponding to modules. In particular it understands how to combine domain-structured module names (org.tfeb.hax.collecting say) with a search list of pathnames to locate a file corresponding to the name which, when loaded, should provide the module. There are mechanisms to define what directories should be searched and in which order, and to wrap code around the process of requiring a module in the manner of CLOS around methods. Finally it also provides a wrapper for provide which keeps a record of the file which provided a given module, which can be used by install-providers (below) to install modules where it expects them to be.

Logical pathnames

require-module doesn’t need you to use logical pathnames, but it does work well with them and I have usually used it that way. Using logical pathnames gives you two advantages:

In summary you don’t have to use logical pathnames, but it can make things easier.

Case

Module names are case sensitive: requireuses string= to compare them. Depending on how you write module names this can make life a little complicated4. This is made more interesting because logical pathnames are really all upper-case. require-module tries to be smart about this:

This typically works reasonably well: if you use module names which are symbols, are searching a physical pathname, and prefer lowercase filenames, then it will find a lowercase filename on the second try.

The search algorithm

The search process starts by splitting up a domain-structured module name into a list of strings, which it will then variously use as directory and name components for the search:

These lists, and parts of them, are then used as parts of pathname specifications after possible case fiddling.

There is a list of path specifications to search: see below for how the list is maintained and exactly what can be in it. A path specification should generally specify a wild or partly-wild lisp source file name. Each path specification is searched in turn, and finally a desperation search is done on all of them using only the last part of the module name. The search continues until either a hit is found or there’s nothing left to search.

Example: searching for :org.tfeb.tools.require-module in "CLEY:LIB;MODULES;*.LISP". This is a logical path specification, so only upper-case variants will be tried. Both the compiled file (via compile-file-pathname) and the source file for the following pathnames will be tried5: if both exist then the compiled file will be taken if it is newer, otherwise the source file (with a warning):

  1. "CLEY:LIB;MODULES;ORG;TFEB;TOOLS;REQUIRE-MODULE;REQUIRE-MODULE.LISP";
  2. "CLEY:LIB;MODULES;ORG;TFEB;TOOLS;REQUIRE-MODULE.LISP";
  3. (all the other path specifications are searched the same way);
  4. "CLEY:LIB;MODULES;REQUIRE-MODULE;REQUIRE-MODULE.LISP"(desperation search, part 1);
  5. "CLEY:LIB;MODULES;REQUIRE-MODULE.LISP" (desperation search, part 2).

Example: searching for "org.tfeb.HAX" in "/local/lisp/*-loader.lisp". This is a physical path specification so things are more complicated:

  1. "/local/lisp/org/tfeb/hax/HAX-loader.lisp"(case as is);
  2. "/local/lisp/org/tfeb/HAX-loader.lisp" (case as is);
  3. "/local/lisp/org/tfeb/hax/hax-loader.lisp" (downcase 1);
  4. "/local/lisp/org/tfeb/hax-loader.lisp" (downcase 2);
  5. "/local/lisp/ORG/TFEB/HAX/HAX-loader.lisp" (upcase 1);
  6. "/local/lisp/ORG/TFEB/HAX-loader.lisp" (upcase 2);
  7. (all the other path specifications);
  8. (equivalent desperation searches, trying downcase and upcase variants as before, a total of 6 more searches).

Package, module, feature

Everything below is exported from org.tfeb.tools.require-module. :org.tfeb.tools.require-module will also be present in both *modules* and *features* once this module is loaded – the latter helps a lot with conditionals in init files.

Requiring and locating modules

require-module will search for and require modules. It has one mandatory argument which is the module name, and a number of keyword arguments:

Wrappers are not yet documented.

require-module returns:

require-module relies on require to do the actual work of loading the file and most of the work of maintaining *modules*. It will only search (and thus only call require on the results of the search) if the module is not already present on *modules*, either because it was not there before the call or because it’s just removed it due to the force option.

It is not an error if a module doesn’t define a package with its own name when the use option is given, but there will be a warning unless quiet is also given.

locate-module locates a module: it’s what require-module uses. It has one mandatory argument which is the module name, and two keyword arguments:

locate-module will return:

The reason for this behaviour is that the file located is often a tiny ‘loader’ shim which never gets compiled6, so in this case there’s nothing wrong if there is no compiled file. If there is a compiled file but it is out of date it’s best to return the source file: it’s current, and anything that calls locate-module can choose to compile the file before loading, which is something require-module can do.

require-modules is a shim around require-module which expects a list of module descriptions instead of a module name. It takes all the same keyword arguments as require-module. A module description is either

In the second case require-module is called with the two sets of arguments appended to each other, with those from the module specification first. Because CL uses the first of any repeated keyword arguments, this means that individual module specifications can override the keyword arguments provided to the function as a whole. require-modules returns a list of lists of the two values returned by each require-module it calls.

requires is a NOSPREAD version of require-modules with a fallback to require: (requires x y) is (require-modules (list x y) :fallback #'require). So requires lets you say that you want one or more modules, and if require-module doesn’t know how to get them then the system should try require in case it does.

needs lets you express a dependency on modules at compile time: it is requires wrapped in a suitable eval-when, but its arguments are quoted. Note that needs quotes its arguments: an older version didn’t so this is an incompatible change. If you use strings or keywords as module names this doesn’t matter, but it makes things like (needs (:org.tfeb.hax.collecting :use t)) more natural7.

The search list

The list of path descriptions is *module-path-descriptions*. Each entry in this list isa path description, which is one of:

The initial value of *module-path-descriptions* is ().

It is perfectly possible to maintain *module-path-descriptions* manually, and that’s how it worked for a long time. There is now a macro which makes this a little easier, perhaps.

define-module-path-descriptions defines module path descriptions. It does this for a particular host (this is one of the reasons logical pathnames are useful), and there are a bunch of options: the most simple ones control whether to add the descriptions before or after the existing ones, and whether to replace existing descriptions for the same host. Rather than describe it in detail here are a couple of examples (yes, this is copping out);

(define-module-path-descriptions ("QL" :after t)
  "QL:LOCAL-PROJECTS;*-LOADER.LISP"
  "QL:LOCAL-PROJECTS;LOADER.LISP"
  "QL:LOCAL-PROJECTS;*.LISP")

This will add a bunch of pathname descriptions for a logical host named "QL and it will add them after any existing ones. It will replace any descriptions for the "QL" logical host.

(define-module-path-descriptions "-"
  (lambda ()
    (make-pathname :name "*-loader" :type "lisp"
                   :defaults (pathname (sb-posix:getcwd))))
  (lambda ()
    (make-pathname :name "loader" :type "lisp"
                   :defaults (pathname (sb-posix:getcwd))))
  (lambda ()
    (make-pathname :name "*" :type "lisp"
                     :defaults (pathname (sb-posix:getcwd)))))

This is from my SBCL init file, where it is the first thing that adds to *module-path-descriptions*. The "-" host doesn’t exist: it’s just there because the macro needs something to be there. Each form in the body is a function which will return a pathname based on the current directory, which means that subdirectories of the current directory get searched first.

There is a weirdness here which is worth noting: define-module-path-descriptions doesn’t normally evaluate the forms in its body. But it does arrange for them to be evaluated if they are lists whose first element is lambda, which is why the above works. This is a horrible hack.

define-module-path-descriptions uses a function called add-module-path-descriptions to do most of its work. You’ll need to look at the source to what it does.

Providing modules

As an interface to install-providers, below, there is a function called provide-module: it does exactly what provide does (it relies on provide to do the work) but also maintains an alist, *module-providers* which maps from module names to the files that provided them (from *load-truename*).

Additionally, provides is a counterpart to requires and needs: it lets you state what module or modules a given file provides. Unlike needs it’s not a macro because modules should not be provided until they are loaded.

Running code after a module is provided

after-require-module is a macro which can be used in a module, to arrange for the forms in its body to be run after the module has been provided. The forms are wrapped in a block also called after-require-module. This can be used any number of times, and if the module is being loaded some other way it will simply do nothing. For example:

(defun interface (...)
  ...)

...

(after-require-module
  (register-interface #'interface))

This is particularly useful for modules consisting of several files (with a ‘loader’ file to load them all): the forms given in after-require-module are run after the whole module is loaded.

Other functionality

There is a mechanism for adding wrappers around the process of actually providing a module (after its file has been located). I’m not going to document this here, but its main use has been to arrange to forget about system definitions for modules which involve some system definition tool, so the LispWorks development environment doesn’t get cluttered up with system definitions that are not interesting. It’s also used to implement after-require-module, above.

Examples

Given

(defvar *my-mpds* '())

(define-module-path-descriptions ("TFB"
                                  :module-path-descriptions *my-mpds*)
  "TFB:LIB;MODULES;*.LISP"
  "TFB:LIB;MODULES;*-LOADER.LISP"
  "TFB:LIB;MODULES;LOADER.LISP")

then

> *my-mpds*
("TFB:LIB;MODULES;*.LISP"
 "TFB:LIB;MODULES;*-LOADER.LISP"
 "TFB:LIB;MODULES;LOADER.LISP")

> (locate-module :org.tfeb.pretend
                 :module-path-descriptions *my-mpds*
                 :verbose t)
Looking for module :org.tfeb.pretend
Probing TFB:LIB;MODULES;ORG;TFEB;PRETEND;PRETEND.LISP
 as     /Users/tfb/lib/lw/modules/org/tfeb/pretend/pretend.lisp
 from "TFB:LIB;MODULES;*.LISP"
Probing TFB:LIB;MODULES;ORG;TFEB;PRETEND.LISP
 as     /Users/tfb/lib/lw/modules/org/tfeb/pretend.lisp
 from "TFB:LIB;MODULES;*.LISP"
Probing TFB:LIB;MODULES;ORG;TFEB;PRETEND;PRETEND-LOADER.LISP
 as     /Users/tfb/lib/lw/modules/org/tfeb/pretend/pretend-loader.lisp
 from "TFB:LIB;MODULES;*-LOADER.LISP"
Probing TFB:LIB;MODULES;ORG;TFEB;PRETEND-LOADER.LISP
 as     /Users/tfb/lib/lw/modules/org/tfeb/pretend-loader.lisp
 from "TFB:LIB;MODULES;*-LOADER.LISP"
Probing TFB:LIB;MODULES;ORG;TFEB;PRETEND;LOADER.LISP.NEWEST
 as     /Users/tfb/lib/lw/modules/org/tfeb/pretend/loader.lisp
 from "TFB:LIB;MODULES;LOADER.LISP"
Probing TFB:LIB;MODULES;PRETEND;PRETEND.LISP
 as     /Users/tfb/lib/lw/modules/pretend/pretend.lisp
 from "TFB:LIB;MODULES;*.LISP"
Probing TFB:LIB;MODULES;PRETEND.LISP
 as     /Users/tfb/lib/lw/modules/pretend.lisp
 from "TFB:LIB;MODULES;*.LISP"
Probing TFB:LIB;MODULES;PRETEND;PRETEND-LOADER.LISP
 as     /Users/tfb/lib/lw/modules/pretend/pretend-loader.lisp
 from "TFB:LIB;MODULES;*-LOADER.LISP"
Probing TFB:LIB;MODULES;PRETEND-LOADER.LISP
 as     /Users/tfb/lib/lw/modules/pretend-loader.lisp
 from "TFB:LIB;MODULES;*-LOADER.LISP"
Probing TFB:LIB;MODULES;PRETEND;LOADER.LISP.NEWEST
 as     /Users/tfb/lib/lw/modules/pretend/loader.lisp
 from "TFB:LIB;MODULES;LOADER.LISP"
nil

But instead if we had

(defvar *my-mpds* '())

(define-module-path-descriptions ("-"
                                  :module-path-descriptions *my-mpds*
                                  :after t)
  "/Local/packages/lispworks/lib/modules/*.lisp"
  "/Local/packages/lispworks/lib/modules/*-loader.lisp"
  "/Local/packages/lispworks/lib/modules/loader.lisp")

then

> *my-mpds*
("/Local/packages/lispworks/lib/modules/*.lisp"
 "/Local/packages/lispworks/lib/modules/*-loader.lisp"
 "/Local/packages/lispworks/lib/modules/loader.lisp")

> (locate-module :org.tfeb.utilities.permutations
                 :module-path-descriptions *my-mpds*
                 :verbose t)
Looking for module :org.tfeb.utilities.permutations
Probing /Local/packages/lispworks/lib/modules/ORG/TFEB/UTILITIES/PERMUTATIONS/PERMUTATIONS.lisp
 from "/Local/packages/lispworks/lib/modules/*.lisp"
Probing /Local/packages/lispworks/lib/modules/ORG/TFEB/UTILITIES/PERMUTATIONS.lisp
 from "/Local/packages/lispworks/lib/modules/*.lisp"
Found /Local/packages/lispworks/lib/modules/ORG/TFEB/UTILITIES/PERMUTATIONS.64xfasl
#P"/Local/packages/lispworks/lib/modules/ORG/TFEB/UTILITIES/PERMUTATIONS.64xfasl"

This second example is betraying the fact that I’m on a Mac: the mac’s filesystem is case-insensitive / case-preserving, so the file is being found with an uppercase filename, when its name is ‘really’ lowercase.

Notes

require-module does quite a lot of processing of pathnames. It is all intended to be portable but it also turns out to explore some of the boundaries of what implementations support. As an example, SBCL can’t currently deal with making partly-wild logical pathnames, so in SBCL you often need to provide stringy logical pathnames in configurations.

All of the functions accept strings or symbols as module names: they’ll complain about anything else rather than blindly calling string.

needs has changed incompatibly so it now quotes its arguments.

Installing modules automagically: install-providers

I now use makefiles to install my personal CL modules and systems, and either ASDF or the LispWorks system definition tool to build them once installed8. Previously I used an ancestor of this code. It lives in the org.tfeb.tools.install-providers package and will add :org.tfeb.tools.install-providers to *modules*.

install-providers will install a set of modules from the files they were originally loaded from into a directory tree under a specified root. It has one argument which is the root under which to install things. The remaining keyword arguments are:

The function returns an alist of (source target) of the files copied.

Example

 > *module-providers*
(("ORG.TFEB.TOOLS.INSTALL-PROVIDERS"
  . #P"/Users/tfb/src/lisp/systems/tools/install-providers.64xfasl")
 ("ORG.TFEB.LW.LW-COMMANDS"
  . #P"/Local/packages/lispworks/lib/modules/org/tfeb/lw/lw-commands.64xfasl")
 ("ORG.TFEB.TOOLS.REQUIRE-MODULE"
  . #P"/Users/tfb/src/lisp/systems/tools/require-module.64xfasl"))

> (install-providers "/tmp/")
Would
 ensure dirs for /tmp/org/tfeb/tools/install-providers.64xfasl
 copy /Users/tfb/src/lisp/systems/tools/install-providers.64xfasl
   to /tmp/org/tfeb/tools/install-providers.64xfasl
Would
 ensure dirs for /tmp/org/tfeb/lw/lw-commands.64xfasl
 copy /Local/packages/lispworks/lib/modules/org/tfeb/lw/lw-commands.64xfasl
   to /tmp/org/tfeb/lw/lw-commands.64xfasl
Would
 ensure dirs for /tmp/org/tfeb/tools/require-module.64xfasl
 copy /Users/tfb/src/lisp/systems/tools/require-module.64xfasl
   to /tmp/org/tfeb/tools/require-module.64xfasl
nil

The TFEB.ORG tools are copyright 2002, 2012, 2020-2021 Tim Bradshaw. See LICENSE for the license.


  1. This README also has footnotes which GitHub does not support. You’ll just have to make sense of that. 

  2. Well, I don’t know how other CL programmers work: I do know that I do this though. 

  3. Or systems in one of the system definition facilities which existed before ASDF, of course. 

  4. I write them as keyword symbols, so my modules always end up with upper-case names. 

  5. Note that, here and below, I am writing pathnames as strings. This is just because I am being lazy: the system works in terms of pathnames, not strings. 

  6. And, in fact, such loader shims often can’t be compiled as they rely on things changing during the load of their source. 

  7. It’s hard to see a case where having needs not quote its arguments is useful since whatever values it uses would need to be available at compile-time anyway, which means you’d already almost certainly have to use eval-when. In any case, if you want what needs does without the autoquoting, you should now use (eval-when (...) (requires ...))

  8. A key to making this work with ASDF is to turn off output translations and keep the compiled files alongside their sources.