Here's my earliest post about keyword args: http://arclanguage.org/item?id=10692. (Follow-up much later: http://arclanguage.org/item?id=13083)

That got me working on a fork of Arc with keyword args support: https://github.com/akkartik/arc. Original discussion about it: http://arclanguage.org/item?id=12657.

That eventually spiraled out into a whole language with easy keyword args at its core: http://akkartik.name/post/wart. Milestones along the way: http://arclanguage.org/item?id=12814; http://arclanguage.org/item?id=12943; http://arclanguage.org/item?id=15180.

Supporting keyword arguments also led me to param aliases: http://arclanguage.org/item?id=15254. Then to Haskell's as-params: http://arclanguage.org/item?id=16970. Then to multi-word functions, kinda inspired by Objective-C's keyword arguments: http://arclanguage.org/item?id=17233.

It's not clear how your macro works, though. When I expand the above call to labels I get this:

  (with (g20467 (fn nil nil)
         g20468 (fn nil nil))
    (with (collatz (fn a (apply g20467 a))
           worker  (fn a (apply g20468 a)))
      (with (collatz (fn (n) (if (even n) (/ n 2) (+ (* n 3) 1)))
             worker  (fn (n seq)
                       (if (is n 1)
                         (cons n seq)
                         (worker (collatz n) (cons n seq)))))
        (do (= g20467 collatz) (= g20468 worker))
        (rev (worker n 'nil)))))

    (labels ((even (n)
               (if (is n 0)
                 'even
                 (odd (- n 1))))
             (odd (n)
               (if (is n 0)
                 'odd
                 (even (- n 1)))))
      (even 5))

    ((fn (g3947 g3948)
      (with (even (fn a (apply g3947 a))
             odd  (fn a (apply g3948 a)))
        (with (even (fn (n) (if (is n 0) (quote even) (odd (- n 1))))
               odd  (fn (n) (if (is n 0) (quote odd) (even (- n 1)))))
          (do
            (= g3947 even)
            (= g3948 odd))
          (even 5))))
     (fn nil nil) (fn nil nil))

    (prn ((fn (g3947 g3948)
            (with (even (fn a (apply g3947 a))
                   odd  (fn a (apply g3948 a)))
              (with (even (fn (n) (if (is n 0) (quote even) (odd (- n 1))))
                     odd  (fn (n) (if (is n 0) (quote odd) (even (- n 1)))))
                (do
                  (= g3947 even)
                  (= g3948 odd))
                (even 5))))
          (fn nil nil) (fn nil nil)))

    ;; odd

    (prn ((fn (g3947 g3948)
            (with (even (fn (n) (if (is n 0) (quote even) (odd (- n 1))))
                   odd  (fn (n) (if (is n 0) (quote odd) (even (- n 1)))))
              (do
                (= g3947 even)
                (= g3948 odd))
              (even 5)))
          (fn nil nil) (fn nil nil)))

    ;; nil

  (with (even nil odd nil)
    (= even (fn (n)
              (if (is n 0)
                'even
                (odd (- n 1))))
       odd  (fn (n)
              (if (is n 0)
                'odd
                (even (- n 1)))))
    (even 5))

    (mac labels (fns . forms)
      (with (fnames (map car fns)
             fbodies (map (fn (f) `(fn ,@(cdr f))) fns))
        `(with ,(mappend (fn (name) `(,name nil)) fnames)
           (= ,@(mappend (fn (f) `(,(car f) ,@(cdr f))) 
                         (zip fnames fbodies)))
           ,@forms)))

    (def collatz-seq (n)
      (labels ((collatz (n)
                 (if (even n)
                   (/ n 2)
                   (+ (* n 3) 1)))
               (worker (n seq)
                 (if (is n 1)
                   (cons n seq)
                   (worker (collatz n) (cons n seq)))))
              (rev (worker n '()))))

    (def parity (n)
      (labels ((even (n)
                 (if (is n 0)
                   'even
                   (odd (- n 1))))
               (odd (n)
                 (if (is n 0)
                   'odd
                   (even (- n 1)))))
              (even n)))

    (prn (macex1 '(labels ((even (n)
                             (if (is n 0)
                               'even
                               (odd (- n 1))))
                           (odd (n)
                             (if (is n 0)
                               'odd
                               (even (- n 1)))))
                          (even n))))

    (prn (parity 17))
    (prn (parity 24))

    (prn (collatz-seq 21))

    ;; ---------------------------------------------

    ;; (with (even nil odd nil)
    ;;   (= even (fn (n)
    ;;             (if (is n 0)
    ;;               (quote even)
    ;;               (odd (- n 1))))
    ;;      odd (fn (n)
    ;;            (if (is n 0)
    ;;              (quote odd)
    ;;              (even (- n 1)))))
    ;;   (even n))
    ;; 
    ;; odd
    ;; even
    ;; (21 64 32 16 8 4 2 1)

Just to add to this, and at the risk of boring the veterans here to death by repeating myself :)

Reading between the lines of the implementation, I think the Arc way of dealing with the possibility of collisions is to not worry about them until they happen. When they happen Arc will show you a warning:

  *** redefining foo

This makes a lot more sense than adding prefixes because the names chosen are in the context of the application being built rather than some one-size-fits-all name chosen by a library. That makes them likely to be better names in the context of the application.

Avoiding prefixes also keeps most names from becoming unnecessarily long when they don't need to be.

I'm talking about "a namespace mechanism" here, without actually knowing how one in Arc would work.

Just thinking about it for a moment, I think you'd set the prefix

  (= namespace-prefix 'awesome-package)

  (def /awesome-function (...)
    (...))

  (w/namespace awesome-package
    ...
    (def /awesome-function (...)
      (...))
    ...)

In the end, you have to have some way of avoiding conflicts -- and all of these boil down to tacking something on the front (math.sqrt in python, for instance); I (personally) would rather have a better way of doing this than manually typing out `awesome-package` at the start of every function/macro/variable/whatever.

I think, given that Arc is supposed to be "a language for good programmers" [1], that it's silly to impose restrictions like withholding a namespacing mechanism to encourage a certain type of programming.

Though I like keeping codebases minimal, I also like freedom.

I try not to use words like 'freedom' in these discussions because navigating by them is a subtle business. While having a feature can sometimes provide freedom, in general I tend to assume that features cost freedom. Like the saying that your possessions own you. A namespace mechanism is more code to write, more places for bugs to be hiding in, more errors for the user to run into, more places for one programmer to hide things where they can trip another programmer up. All these issues are places for degrees of freedom to be used up rather than created.

So rather than importing a single big library in your application, you would instead import a lot of micro libraries (each of which is versioned separately, and might have their own dependencies).

What I would like to happen is that my application only contains dependencies it really needs, and that each dependency includes no superfluous/dead interfaces or code. Under these circumstances I would like to live in a world where I can go in and modify the libraries to have different names, with the difference in names making sense in the context of the application. Then I would bundle the application with all its libraries included.

Of course this doesn't scale to large libraries, because managing a fork today involves an amount of work that ranges from non-trivial to intractable. But this would be my ideal.

Past writings on this subject: http://akkartik.name/post/libraries; http://akkartik.name/post/libraries2. My current project which tries to make fork-management tractable: https://github.com/akkartik/mu

  Unrecorded reasoning, existing mainly in our minds.
  -->
  Codebases dedicated to proofs or tests.
  -->
  Proofs or tests located in the codebase they apply to.
  -->
  A type/contract declaring a module interface.
  -->
  A type/contract annotation for a function definition.
  -->
  A type/contract annotation for an individual expression.
  -->
  A type/contract annotation for an individual built-in operator, but at
  this point it becomes implicit in the operator itself, and we just
  have structured programming, enjoying properties by construction.

  Unrecorded how-to knowledge, existing mainly in our minds.
  -->
  Codebases or how-to guides dedicated to curated builds (e.g. distros).
  -->
  Build scripts and docs located in the codebase they apply to.
  -->
  Macroexpansion-time glue code, importing compiler extensions by name.
  -->
  Load-time glue code, importing runtime extensions by name.
  -->
  Service-startup-time glue code, obtaining dependency-injected fields
  by name.
  -->
  An expression, taking free variables from its lexical scope by name.
  (This is a build at "evaluation of this particular expression" time.)

And this means that even local syntactic concerns extrapolate to social decisions about how we expect to deal with our unrecorded knowledge. Every design decision has a lot to go by. :)

---

Another exciting part is that I think nested quasiquotation shows us a more general theory of lexical locality. If we're dealing with syntax as text, then locations in that text have an order, and we can isolate code snippets at intervals along that order (and mark them with parentheses). Intervals are partially ordered by containment, so we can isolate code snippets at meta-intervals between an outer interval and multiple nonoverlapping inner intervals (and mark them with parentheses with nonoverlapping parentheses-shaped holes: quasiquotations).

That "nonoverlapping" part seems awkward, but I think there's a simple concept somewhere in here.

With this concept of intervals, I'm considering higher degrees of lexical structure past quasiquotation, and I'm considering what kind of parentheses or quasiquotations would exist for non-textual syntaxes.

A module system deals with a non-textual syntax: The syntax of a bundle of modules. If the modules have no order to them, then we don't even have parentheses to work with, let alone quasiquotation. But they can have an order to them. We can impose one from outside:

  Module A precedes module B.

  Module A says, "..."
  Module B says, "..."
  Module C says, "Module A precedes module B."

  Module A says, "..."
  Module B says, "..."
  Module C says, "Module A precedes module B."
  Module D says, "Module B precedes module A."
  Module E says, "If module C and module D disagree, listen to module C."
  Module F says, "If module C and module D disagree, listen to module D."
  Module G says, "If module E and module F disagree, listen to module E."

With this ability to disambiguate when things go wrong, we can model lexical scope:

  Module A says, "Export foo = (import bar from system {B, C})."
  Module B says, "Export foo = 2."
  Module C says, "Export bar = foo + foo."
  
  Result: foo = 4.

If we really want access to bar at the top level, we can refer to it again, and we can even be sloppy about it and make up for our sloppiness with disambiguations:

  Module A says, "Export foo = (import bar from system {B, C})."
  Module B says, "Export foo = 2."
  Module C says, "Export bar = foo + foo."
  
  Module D says, "Export all imports from system {B, C}."
  Module E says, "If A and D export the same variable, listen to A."
  
  Result: foo = 4; bar = 4.

  Module A says, "Export foo = (import bar from system {B, C})."
  Module B says, "Export foo = 2."
  Module C says, "Export bar = foo + foo."
  
  Module D says, "Export all imports from system {A, B, C}."
  Module E says, "Export all imports from system {C, F}."
  Module F says, "Export foo = (import foo from system {A, B, C})."
  Module G says, "If D and E export the same variable, listen to D."
  
  Result: foo = 4; bar = 8.

  Module A says, "Export foo = (import bar from range R1)."
  Module B says, "Export interval R1, and begin it here."
  Module C says, "Export foo = 2."
  Module D says, "Export bar = foo + foo."
  Module E says, "End interval."
  Module F says, "These modules are in order: B, C, D, E."

Do you want to avoid the situation, wich happens in c, where when you need the sqrt you have to include the whole math file? I totally agree.

>Under these circumstances I would like to live in a world where I can go in and modify the libraries to have different names, with the difference in names making sense in the context of the application

This looks right to me. Perhaps it could be something like python's

    from library import function as good_name_for_your_project

Yes, definitely. In the Javascript world it's called tree-shaking: https://medium.com/@Rich_Harris/tree-shaking-versus-dead-cod...

> from library import function as good_name_for_your_project

What's happening here is that you're a) adding a feature in Python to support 'from..as', b) including an external library and c) continuing to keep around an old name that you don't really care about. You're essentially preserving the old name just because other people who your application doesn't care about use it.

Imagine a world where maintaining forks was tractable. Would this still be a good idea? Why not just do a search and replace and maintain a private fork, eliminating all this complexity in your private stack? Just delete 'from..as' from your private Python! :o)

> I'm not sure making a copy of a library is a good idea because it would lead the user to have many copies of the same libraries.

Yes, this is a fundamental difference in outlook/ideology. I think that copying isn't always bad. We culturally tend to emphasize the issues with copying a lot more than the costs of avoiding duplication.

A degenerate example is to observe that there are tons of 'e's in the novel I'm reading and try to deduplicate them. That is of course obviously farcical, but it at least serves to illustrate that there's a trade-off, and that always DRY'ing your code isn't obviously a good idea. Another example is to observe that the internet has many copies of the same libraries running at any given time. You can argue that they're on different machines, but then imagine a 'machine' consisting of multiple cores and private caches and non-uniform memory access and RAID-partitioned disks. Changing latency costs can make it reasonable to maintain multiple copies of some immutable data in a single 'machine'. Now consider that development is yet another cost that is open to variation. If (automatically) creating copies of something eases development, it's at least worth considering. For example, optimizing compilers can sometimes specialize a function differently for different callsites. That's duplication often inside a single binary, and it makes sense in some contexts.

Duplicating libraries isn't a problem: disk space for ease of development is an exchange which is getting more and more convenient.

Or, if it all needs to be bundled, you could have symlinks for the libraries you don't change.

If a name's already good, you're not going to change it; if it's bad, you should push that change upstream! (If the name's bad, it's likely that the original author didn't put much time into choosing the name, so I think it would be fairly straightforward to get that merged.)

But it's not just names per se. In that side-by-side comparison, they might also want to merge and branch parts of the code whose assumed invariants have now changed; invariants can act as Schelling points, like invisible names. Modifying code is something we do sometimes, and I think akkartik wants to see how much simplicity we'll get if everyone who wants a simpler system has the tooling support to modify the code and make it simpler themselves.

Personally, I find it fascinating how to design a language for multiple people to edit the code at the same time, a use case that can singlehandedly justify information hiding, modules, and versioning. But I think existing module systems enforce information hiding even more than they have to, so that in the cases where people do need to invade that hidden information, they face unnecessary difficulties. I think a good module system will support akkartik's way of pursuing simplicity.

But... my module system ideas aren't finished. At a high level:

- You can invade implementation details you already know. You can prove this by having their entire code as a first-class value with the expected hash.

Not necessarily. 'Good' and 'bad' are not absolute, they are extremely contextual. A name that is good for a general-use library might be sub-optimal for your application, or vice versa. Subjective taste is also a thing. So while you should certainly send out a pull request for the change, our model of the world shouldn't rely on the change actually getting pushed.

In general it is amazing to me how often a blindingly obvious Pull Request gets rejected or just sits in the queue, untouched. There's lots of different kinds of people out there. Which is why I tend to think more like a barbarian[1] about collaboration: think of other people as islands with whom you might collaborate if the stars align. But don't rely on the collaboration. Be self-sufficient.

[1] http://www.ribbonfarm.com/2011/03/10/the-return-of-the-barba...

---

"As much as I love this idea of implicit importing, I'm sure the explicit side -- which'll let you change whatever names you like -- will need to be there as well."

I actually interpreted your original post that kicked off this thread as implicit loading since Arc has no notion of modules or import. So the question of changing names did not arise. That seemed like a tangent to the original question.

These seem like separate questions:

1. Should Arc know how to react with implicit symbols?

2. Should Arc provide namespaces?

One the one hand, you can have implicit loading without needing a module/namespace system. On the other hand, I don't see how you can have implicit loading in the presence of namespaces. Without the "from..as" construct how would your system know which library to load a symbol from, if there's a collision?

From what I can see, you have to install (npm's equivalent of) the standard libraries you want in to the node_modules dir. (So it's not much of a win over the boilerplate import code.)

I wonder if there's a way to make (fn (x) ...) even more lightweight.

What if, to do the same thing, we had a new anonymous function syntax?

    {x ...}

    arc> (let my-fn {arg (string "I got " arg)}
              (my-fn "this thing"))
    "I got this thing"

    (let x ...)

    {(x y} ...)

    {{x y} ...};; this would be non-destructuring-bind
    {(x y) ...};; this is destructuring-bind
    {{(x y} ...);;; this is the same as #2; it would destructuring-bind the first argument, a list.

    [{x y} ...]

    (fn (x y) ...)

    ([prn _1 _2] "hello " "there")

    ([((a b) c) (prn c b a)] (list "is" "name ") "my ")

But this interferes with the arc special syntax of having lists act as functions on their indices. Because the following is already valid arc code:

    (let x (list 1 2 3)
      (x 2))
    ;; > 3

    (let x (list 1 2)
      ({((a b) c) (prn c b a)} x 3))

    (with (f {((a b) c)
               (prn c b a)}
           x (list 1 2))
      (f x 3))

> In that case having different delimiters might be the way to go. So your brace notation would be used for anonymous functions with full lambda list capability.

Yeah, I think you're right. The square-brace anonymous function could have optionally a curly-braced first argument. If that argument isn't there, it works as the square-braced anonymous function currently does. If that argument is there, it's the arguments to that function. Since curly braces aren't used anywhere else in Arc, it can only be parsed in that one way.

I don't think even the [] syntax really pulls its weight. Between (foo [bar baz _]) and (foo:fn_:bar baz _), the latter is already more convenient in some ways, and one advantage is that we can define variations of (fn_ ...) under different names without feeling like these variations are second-class.

a) what version of asdf (and sbcl and OS and processor...) you have tried and seen it working on,

b) which directory you put Clamp in when you clone it,

c) which directory you run sbcl from, and

d) what commands you use to load clamp after starting sbcl?

It would only take a few sentences/minutes, and it'll help immeasurably to get people unfamiliar with Common Lisp started with Clamp. Telling people how to get up and running (without needing to understand the dependencies you rely on) is the bare minimum prerequisite necessary to contemplate replacing Arc-on-Racket with Clamp-on-Common-Lisp.

It seems not a month passes without some new project I would find most interesting to try out, except it doesn't have a Readme, or it has a Readme with tons of prose except for the one primary thing I care about in the beginning: what are the precise concrete commands that have been known to have it do something, at least on some one computer? It's a super easy way to stand out among the crowd, and it only takes a few sentences compared to the thousands of lines of code you've already written.

[1] http://www.arclanguage.org/item?id=18895

  $ sudo apt-get install emacs
  $ emacs --version
  GNU Emacs 24.3.1

  $ cat .emacs
  ; from http://melpa.org/#/getting-started
  (require 'package) ;; You might already have this line
  (add-to-list 'package-archives
               '("melpa" . "https://melpa.org/packages/"))
  (when (< emacs-major-version 24)
    ;; For important compatibility libraries like cl-lib
    (add-to-list 'package-archives '("gnu" . "http://elpa.gnu.org/packages/")))
  (package-initialize) ;; You might already have this line

  ; from https://www.common-lisp.net/project/slime/doc/html/Installation.html
  (setq inferior-lisp-program "/usr/bin/sbcl")

  $ pwd
  /home/akkartik
  $ ls common-lisp
  Clamp/

  $ emacs
  M-x package-install RET slime RET
  # some errors
  M-x slime
  # seemed to work
  * (require :clamp)
  Don't know how to REQUIRE CLAMP.
     [Condition of type SB-INT:EXTENSION-FAILURE]

I didn't think this was a problem since https://common-lisp.net/project/asdf/#downloads suggested just using the version that comes with my CL. Should I upgrade my sbcl as well?

Everytime I consider installing asdf manually I'm stymied by that last link. It provides an asdf.lisp but doesn't say what to do with it. Do I just load it? I just tried that without luck. I also tried various incantations from these tabs I have open: https://www.common-lisp.net/project/asdf-install/tutorial/in...; https://www.common-lisp.net/project/asdf-install/tutorial/se....

Common Lisp's crap documentation is culturally recursively turtles all the way down, just like all the good things about it.. :/ This is why I'm rooting for you to break out of this cycle of suck and improve things. Would you consider starting with a pristine Ubuntu 14.04 without sbcl or anything on it, and saving all the commands you type in until you get to a working Clamp? That would be wonderful to include in the Readme.

Another option might be to eschew asdf since the default versions on the most common Ubuntu release interact so poorly. Just dump all notion of dependencies and directly include all the code you need in the appropriate relative paths. Give me a single "sbcl --load" command to rule them all, just like Arc 3.1's classic "racket -f as.scm".

(It's not just Common Lisp, by the way. I have yet to meet a language-specific package manager that didn't suck. Pip, RubyGems, CPAN, it's all utter garbage. NPM hasn't started to suck yet, but I'm constantly looking for signs of incipient over-complexification.)

No. It's just that asdf >=3.1.2 will check the ~/common-lisp directory by default. Prior to 3.1.2, you had to manually specify the directories you wanted asdf to check.

> https://common-lisp.net/project/asdf/#downloads suggested just using the version that comes with my CL. Should I upgrade my sbcl as well?

It looks like the version of sbcl you are using is old enough that the asdf version it comes with is older than 3.1.2. From that link, there is https://common-lisp.net/project/asdf/asdf.lisp Copy paste that into a file and add `(load "/foo/bar/asdf.lisp")` to your .sbclrc. I believe that Quicklisp comes with a more recent version of asdf, so you can also try setting that up and seeing if that configures asdf properly.

> I also tried various incantations from these tabs I have open

Those are for asdf-install which IS NOT asdf: http://www.cliki.net/asdf-install

asdf-install was the previous version of Quicklisp, but you should now be using Quicklisp instead.

> Those are for asdf-install which IS NOT asdf: http://www.cliki.net/asdf-install

  $ sudo apt-get install sbcl
  $ wget https://beta.quicklisp.org/quicklisp.lisp  # following instructions at https://quicklisp.org
  $ sbcl --load quicklisp.lisp
  * (quicklisp-quickstart:install)
  * (ql:add-to-init-file)
  * (quit)
  $ cd quicklisp/local-projects
  $ git clone https://github.com/malisper/Clamp

  $ sbcl
  * (ql:quickload :clamp)
  * (in-package :clamp)
  * (use-syntax :clamp)

  * (map [+ _ 1] '(1 2 3))
  (2 3 4)

  $ cat quicklisp/local-projects/Clamp/init.lisp
  (ql:quickload :clamp)
  (in-package :clamp)
  (use-syntax :clamp)
  $ sbcl --load quicklisp/local-projects/Clamp/init.lisp
  ; Loading "clamp"
  * (map [+ _ 1] '(1 2 3))
  The variable [+ is unbound.

You might want to consider trying to setup Slime, as it provides some really amazing Smalltalk-esque features. I detailed most of them in my blog series, Debugging Lisp[0]. Some of the ones I covered in the post are: recompilation of code at runtime, restarting of a stack frame at runtime, an object inspector, interactive restarts (restarts are a better form of try/catch), various forms of function lookup (e.g. list all functions who call function X). I haven't yet covered it, but I eventually want to, is slime-macrostep[1]. It lets you interactively expand parts of a macro step by step.

[0] http://malisper.me/2015/07/07/debugging-lisp-part-1-recompil...

  Cannot restart frame: #<SB-DI::COMPILED-FRAME EVAL>

  $ clamp

  $ emacs
  M-x slime RET
  # in the slime buffer
  * (ql:quickload :clamp)
  * (in-package :clamp)
  * (use-syntax :clamp)

Yes, that's what I typically do. If you wanted to, you could add those instructions to your .sbclrc, and that should load Clamp on start up.

> Also, when I try to C-x C-e an arc expression in some random buffer after the above steps, it doesn't seem to remember the above commands anymore.

You need to have slime-mode enable in the buffer you are editing. You can add the following code to your .emacs:

    (require 'slime)
    (add-hook 'lisp-mode-hook (lambda () (slime-mode t)))

Yes, customizing Emacs is really useful for making it better to use. To help with that, here are some of my config's settings for things you've mentioned. My show-paren-mode settings are here (https://bitbucket.org/zck/.emacs.d/src/default/init.el?filev...).

Instead of paredit, I use smartparens. They do similar things, but when I looked at the two, I thought smartparens was better, although I can't remember why right now. My config is here (https://bitbucket.org/zck/.emacs.d/src/default/init.el?filev...).

We need a compiler for that btw (ie. the arc macro Im talking about nearby?) because 1) language designers need a compiler and 2) right now, it is missing parts of Arc; specifically:

  ('(1 2 3) 0)
  (mylist 0)
  ("Yoopi" 0)
  (+ "Hello" " World")
  top level ssyntax
  What case are missing for destructuring?
  What am I forgetting? Do we have 'for'?

Run your lisp wherever you want and then:

  (asdf:load-system :clamp)
  (defpackage #:mypkg (:use clamp))
  (in-package #:mypkg)

> Telling people how to get up and running

  $ uname -a
  Linux akkartik 3.5.0-17-generic #28-Ubuntu SMP Tue Oct 9 19:32:08 UTC 2012 i686 i686 i686 GNU/Linux

  $ pwd
  /home/akkartik

  $ sbcl --version
  SBCL 1.1.14.debian

  $ ls quicklisp/local-projects
  Clamp/  system-index.txt

  $ rlwrap sbcl
  This is SBCL 1.1.14.debian, an implementation of ANSI Common Lisp.
  More information about SBCL is available at <http://www.sbcl.org/>.

  SBCL is free software, provided as is, with absolutely no warranty.
  It is mostly in the public domain; some portions are provided under
  BSD-style licenses.  See the CREDITS and COPYING files in the
  distribution for more information.
  * (require :asdf)

  ("ASDF")
  * (asdf:load-system :clamp)

  debugger invoked on a ASDF/FIND-SYSTEM:MISSING-COMPONENT in thread
  #<THREAD "main thread" RUNNING {ABFC8D1}>:
    Component :CLAMP not found

  Type HELP for debugger help, or (SB-EXT:EXIT) to exit from SBCL.

  restarts (invokable by number or by possibly-abbreviated name):
    0: [ABORT] Exit debugger, returning to top level.

  ((:METHOD ASDF/OPERATE:OPERATE (SYMBOL T)) ASDF/LISP-ACTION:LOAD-OP :CLAMP) [fast-method]
  0]
  *