I put failing.asd
(in-package :asdf-user)
(defsystem "failing"
:description "some code destined to fail"
:version "0.1"
:author "me"
:components ((:file "package")))
and package.lisp
(defpackage :failing
(:export :foo :bar))
(in-package :failing)
(defun foo () 42)
(defmacro bar ()
(let ((x (foo)))
`(print ,x)))
(bar)
into ~/quicklisp/local-projects/failing. Using Clozure CL with Quicklisp installed, I run
(ql:quickload :failing)
which gives me
To load "failing":
Load 1 ASDF system:
failing
; Loading "failing"
[package failing]
> Error: Undefined function FOO called with arguments () .
> While executing: BAR, in process listener(1).
> Type :GO to continue, :POP to abort, :R for a list of available restarts.
> If continued: Retry applying FOO to NIL.
> Type :? for other options.
It seems I can't call a function from a macro inside the package. Why not?
That can only happen when the file gets compiled before loaded. Generally it has nothing to do with ASDF (which is a tool to manage file dependencies and to compile/load code) or packages (which are namespaces and are not in any way related to ASDF).
It has to do with how file compilation works in Common Lisp:
The file compiler sees the function foo and compiles it -> the code for it gets written to a file. It does not (!) load the code into the compile-time environment.
The file compiler then sees the macro bar and compiles it -> the code gets written to a file. It does (!) load the code into the compile-time environment.
The file compiler then sees the macro form (bar) and wants to expand it. It calls the macro function bar. Which calls foo, which is undefined, since it is not in the compile-time environment.
Solutions:
put the function definition in a separate file in the ASDF system and compile/load it earlier.
put the function inside the macro as a local function
put (EVAL-WHEN (:COMPILE-TOPLEVEL :LOAD-TOPLEVEL :EXECUTE) ...) around the function definition. It causes the definition to be executed at compile-time.
Remember: the file compiler needs to know macro functions -> otherwise it would not be able to macroexpand code. Ordinary functions just get compiled, but not loaded at compile time, during compilation of a file.
Related
Lets say i define a macro
(defmacro foo(x)
(print x))
Now i want to be able to always load this macro in all my lisp files in future where should i save this macro?
Every CL implementation has an init file it calls on start. For SBCL that is ~/.sbclrc. Usually also quicklisp has some setup code in there if you installed quicklisp.
So you could add a line:
(load #P"path/to/your/macro/file.lisp")
And it'll get loaded each time you start SBCL.
You want to have a library.
A library can contain any number of definitions, not only macros.
The de facto standard way to define systems (which is a more general term for libraries, frameworks, and applications — units of software) is to use ASDF.
Let's say that you put your macro into a lisp file:
;;;; my-util.lisp
(in-package cl-user)
(defpackage my-util
(:use cl))
(in-package my-util)
(defmacro foo (x)
`(whatever ,x etc))
Then you put that under a directory that is known to ASDF. One useful directory for that is ~/common-lisp/, so let's use ~/common-lisp/my-util/. In the same directory, put the system definition file:
;;;; my-util.asd
(in-package asdf-user)
(defsystem "my-util"
:components ((:file "my-util")))
Now you can load this utility into any lisp interaction, e. g. on the repl:
CL-USER> (asdf:load-system "my-util")
Or in a different system:
;;;; my-application.asd
(in-package asdf-user)
(defsystem "my-application"
:depends-on ("my-util")
...)
In the case of utility libraries, you often want to use their package so that you don't need to package-qualify the symbols.
If you want things that only work on your computer (like shortcuts for your REPL use or one-off scripts), you can sometimes get away with adding things to your implementation's init file.
This is example.lisp:
(defun f (x)
(* x 2))
(defconstant +n+ (f 1))
When I compile try to compile the file using (compile-file "example.lisp"), I get an error when compiling the constant: The function COMMON-LISP-USER::F is undefined. How can this be? I have already defined the function f before using it to define the constant. How do I define a constant whose value is the return value of a function?
I am using SBCL 2.0.1.
From DEFCONSTANT:
[...] users must ensure that the initial-value can be evaluated at compile time (regardless of whether or not references to name appear in the file) and that it always evaluates to the same value.
But COMPILE-FILE and 3.2.3 File Compilation only require the DEFUN form to establish that F exists, not that is may be evaluated during compilation.
You need to LOAD the resulting file for the definition to be available in your environment (e.g. Slime compiles a file and loads the result). Likewise, when you evaluate forms one at a time in the REPL, the definition becomes available right away, as-if a small compile-load cycle was done.
You have two main options:
wrap the defun in an eval-when form
(eval-when (:compile-toplevel :load-toplevel :execute)
(defun f (x) (* x 2)))
put the two forms in distinct files, and have the second one depends in the system (in the defsystem sense) on the first one:
(defsystem "foo"
:components ((:file "define-f")
(:file "define-constant"))
:serial t)
I want to create a source file in which most of the functions there defined, are local to that source file. It's the same purpose that would be served in C by marking the functions static; in C++ one could also surround them with namespace { ... }. I get the impression in Lisp, the package system is the appropriate tool. However, my attempts so far are not working.
This is what I currently have, but SBCL rejects it with the claim that global-fun is undefined. Explicitly referring to it as cl-user:global-fun, produces similar results. What should I be doing?
(defun global-fun ()
(format t "global~%"))
(defpackage :local-package
(:use :common-lisp)
(:use :cl-user))
(in-package :local-package)
(defun local-fun ()
(global-fun)
(format t "local~%"))
You're nearly there. You might use Slime's autocompletion to find out.
Either export global-fun, or access it with a double colon: (cl-user::global-fun).
With another global-package:
(defpackage :global-package
(:use :common-lisp) ;; <-- can be :cl
;; (:use :cl-user) <-- not necessary
(:export :global-fun))
(in-package :global-package)
(defun global-fun () …)
(defpackage :local-package
(:use :cl
:global-defun)) ;; <-- one ":use" is possible
(in-package :local-package)
; etc
There seem to be some misconceptions here.
There is no such thing as a “global function” in Common Lisp. The thing you defined first in your file, global-fun is in some package, most likely the cl-user package.
There is also no direct correspondence between packages and files. You can define things for different packages in a single file, and you can define things for a single package in multiple files. To make things unambiguous and easy to read, there is a very sensible convention to always start a source file with an in-package form (in some styles preceded by a defpackage form), and to never put another in-package somewhere later in the file.
When you write a symbol without package, e. g. somefun or myarray, it is interned (i. e. a sort of idempotent registration) into the current package (see below what that is). This is independent from whether you currently define something or refer to it, because it is done by the reader when reading your source code forms. In both of the following forms, the symbol named foo is interned into the current package (and both result in the identical symbol to be used):
(defun foo ()
…)
(foo)
In order to refer to a symbol from a different package, you need to put the package name as a prefix with :: as separator, as in my-package::foo, but this is usually a code smell because…
… you should export any symbols that a user of your package is intended to use, from your package definition:
(defpackage my-package
(:use common-lisp)
(:export foo))
You can refer to exported symbols from another package with a single colon as separator, as in my-package:foo, and this is good style.
Now, the current package is just the value of the variable *package*. If you look at it from the point of view of a REPL session, this is the argument of the most recent in-package call. In the context of whole file compilation, it is the value of the lexically closest preceding in-package form. In the context of single-form compilation in a file, the IDE will (in any case I have seen) look for that preceding in-package form even if it is not evaluated explicitly. In a pristine Lisp image, the starting package is common-lisp-user, which has a nickname cl-user.
I'm using HT-SIMPLE-AJAX to provide a simple JSON structure over AJAX. It works beautifully if the function defined by defun-ajaxis compiled after the lisp image and the server is started.
If I load the lisp program (with ccl --load) with the function defined, I get this error:
Error: Unbound variable: *AJAX-PROCESSOR*
While executing: #, in process listener(1).
Type :GO to continue, :POP to abort, :R for a list of available restarts.
If continued: Skip loading "/home/hunchentoot/quicklisp/local-projects/gac-man/run.lisp"
Type :? for other options.
The function is as follows:
(defun-ajax machine-info (serial) (*ajax-processor*)
(let* ((serialn (remove #\" serial)))
(concatenate 'string
"Lots of boring stuff" "here")))
The ajax processor is created in another function, called at the start of the program:
(defun start ()
(setup)
(connect-to-database)
(defvar *web-server* (start (make-instance 'hunchentoot:easy-acceptor :port 8080
:document-root #p"~/www/")))
(defvar *ajax-processor*
(make-instance 'ajax-processor :server-uri "/ajax"))
(print "Starting web server...")
(setf *show-lisp-errors-p* t
*show-lisp-backtraces-p* t)
(define-easy-handler (docroot :uri "/") () (docroot)
....
....
(setq *dispatch-table* (list 'dispatch-easy-handlers
(create-ajax-dispatcher *ajax-processor*)))))
And yet if I start everything and then compile in the function through slime later, it works just fine. Why is this error occurring?
I'm using Clozure Common Lisp on 64-bit Linux.
It seems that your defun-ajax form is loaded before the start function has run. That is not surprising. Usually, all code is loaded, and only then the entry point is called.
You should always be very suspicious of defvar, defun, defparameter etc. forms appearing in a function body. They don't belong there. Put them as toplevel forms, so they are loaded as part of the program. Most of the things defined during the run of the start function shown should really be toplevel forms.
Here's a strange situation. I have this code:
(eval-when (:compile-toplevel :load-toplevel :execute)
(ql:quickload "cffi-grovel")
(setf cffi-grovel::*cc* "mpicc")) ; <--- this is the line it complains about.
Which I belive has to load cffi-grovel package before setting cffi-grovel::*cc* variable. When this form is executed from SLIME it works, but it doesn't work when loaded directly by SBCL, here's the output:
$ sbcl --noinfo
* (ql:quickload "cl-mpi")
debugger invoked on a LOAD-SYSTEM-DEFINITION-ERROR in thread
#<THREAD "main thread" RUNNING {10029C0E43}>:
Error while trying to load definition for system cl-mpi from pathname
/home/wvxvw/quicklisp/local-projects/cl-mpi/cl-mpi.asd:
READ error during COMPILE-FILE:
Package CFFI-GROVEL does not exist.
Line: 6, Column: 25, File-Position: 264
< restarts ... >
* (ql:quickload "cffi-grovel")
To load "cffi-grovel":
Load 1 ASDF system:
cffi-grovel
; Loading "cffi-grovel"
..
("cffi-grovel")
* (ql:quickload "cl-mpi")
To load "cffi-grovel":
Load 1 ASDF system:
cffi-grovel
; Loading "cffi-grovel"
To load "cl-mpi":
Load 1 ASDF system:
cl-mpi
; Loading "cl-mpi"
; mpicc -m64 ...
; ...
.
("cl-mpi")
Why does it fail the first time?
PS. I also tried #.cffi-grovel::*cc* instead - same result.
It fails because Lisp reads every form before executing it. And when it reads it, package cffi-grovel indeed does not exist yet, because cffi-grovel is loaded at execution time (whatever it means for form wrapped with eval-when).
Try spliting the eval-when form into two eval-whens: ql:quickload and setf. Or write something like this:
(setf (symbol-value (find-symbol "*CC*" "CFFI-GROVEL"))
"mpicc")
monoid gives a good answer. Here is a slightly shorter form.
Find the symbol at runtime, when the package actually exists. Note the use of SET, not SETF here:
(set (find-symbol "*CC*" "CFFI-GROVEL") "mpicc")
To make it more robust, one would need to check that FIND-SYMBOL actually finds the symbol.
The following function also gives you meaningful error messages and restarts:
(defun set-runtime-symbol (name package value)
(assert (find-package package) (package))
(assert (find-symbol name package) (name))
(set (find-symbol name package) value))
Alternatively use two EVAL-WHEN statements, instead of one.
OK, finally figured it I can do it like so:
(setf #.(intern "cffi-grovel::*cc*") "mpicc")
But I'm not sure how much this is fail-safe.