Hy equivalent to * operator in Python's function arguments that forces keyword arguments - hy

Recently I have been trying to write a simple bot in Hy with Discord.py. In Discord.py we can write a command like this to turn the last argument into a full string that includes spaces:
#commands.command(description="", help="")
async def say(self, ctx, level, *, remains):
...
But if I write this in Hy as:
##((commands.command :description "" :help "")
(defn/a say [self ctx level * remains]
...))
It will complain about missing required argument "text." What's even weirder is that the sample code in the defn part on Hy's official website:
(defn compare [a b * keyfn [reverse False]]
(setv result (keyfn a b))
(if (not reverse)
result
(- result)))
doesn't even work under hy --spy. Did I use it wrong or there's a correct way to handle this?


(defn compare…) works for me. Sounds like the version of Hy you're running doesn't match the version of the documentation you're reading.

Related

Requiring `hy' macro with `raise' function triggers `raise' on `require'

When trying to require the following macro in another file, the raise seems to be triggering immediately:
(defmacro assert [a [b True] [message None]]
`(unless (= ~a ~b) (raise (AssertionError (or ~message ~a)))))
This results in an AssertionError: True.
Steps to reproduce (sometimes works, and sometimes doesn't):
echo '(defmacro assert [a [b True] [message None]] `(unless (= ~a ~b) (raise (AssertionError (or ~message ~a)))))' > a.hy
echo '(require a [assert])' > b.hy
echo '(assert True)' >> b.hy
hy b.hy

In another instance of Python evaluating function arguments before names, as stated by Kodiologist in their comment here and their answer on one of my previous questions "Non-existent hy macros runs assertions, but fails appropriately with everything else", the issue was that unless didn't trigger a NameError when it didn't exist, since it was moved from the hy core to hyrule a little over a year ago.

difference yap and swi-prolog reading canonical lists

I have the following test code trying to read file into a list
open('raw250-split1.pl', read, Stream),
read(Stream,train_xs(TrainXs)),
length(TrainXs, MaxTrain).
I will omit part of the output due to the file is quite large.
It works well with yap,
➜ chill git:(master) ✗ yap [18/06/19| 5:48PM]
% Restoring file /usr/lib/Yap/startup.yss
YAP 6.2.2 (x86_64-linux): Sat Sep 17 13:59:03 UTC 2016
?- open('raw250-split1.pl', read, Stream),
read(Stream, train_xs(TrainXs)),
length(TrainXs, MaxTrain).
MaxTrain = 225,
Stream = '$stream'(3),
TrainXs = [[parse([which,rivers,run,through,states,bordering,new,mexico,/],answer(_A,(river(_A),traverse(_A,_B),next_to(_B,_C),const(_C,stateid('new mexico')))))],
<omited output>
,[parse([what,is,the,largest,state,capital,in,population,?],answer(_ST,largest(_SU,(capital(_ST),population(_ST,_SU)))))]]
But on swi-prolog, it will produce Type error
➜ chill git:(master) ✗ swipl [18/06/19| 7:24PM]
Welcome to SWI-Prolog (threaded, 64 bits, version 7.6.4)
SWI-Prolog comes with ABSOLUTELY NO WARRANTY. This is free software.
Please run ?- license. for legal details.
For online help and background, visit http://www.swi-prolog.org
For built-in help, use ?- help(Topic). or ?- apropos(Word).
?- open('raw250-split1.pl', read, Stream),
read(Stream, train_xs(TrainXs)),
length(TrainXs, MaxTrain).
ERROR: raw250-split1.pl:4:
Type error: `list' expected, found `parse(which.(rivers.(run.(through.(states.(bordering.(new.(mexico.((/).[])))))))),
<omited output>
,answer(_67604,(state(_67604),next_to(_67604,_67628),const(_67628,stateid(kentucky))))).[].(parse(what.((is).(the.(largest.(state.(capital.(in.(population.((?).[])))))))),answer(_67714,largest(_67720,(capital(_67714),population(_67714,_67720))))).[].[]))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))' (a compound)
In:
[10] throw(error(type_error(list,...),context(...,_67800)))
[7] <user>
Note: some frames are missing due to last-call optimization.
Re-run your program in debug mode (:- debug.) to get more detail.
What might be the problem for the error here?
File raw250-split1.pl can be found from the ftp url below, if you'd like to try it.
Thank you for the help!
I am trying to migrate an earlier code to SWI-Prolog, which was written in
SICStus 3 #3: Thu Sep 12 09:54:27 CDT 1996 or earlier
by Raymond J. Mooney ftp://ftp.cs.utexas.edu/pub/mooney/chill/.
All the questions with this tag are all related to this task. I'm new to prolog, helps and suggestions are welcomed!

The raw250-split1.pl was apparently written using canonical notation. The traditional list functor is ./2 but SWI-Prolog 7.x changed it to '[|]'/2 in order to use ./2 for other purposes. This results in the the variable TrainXs being instantiated by the read/2 call to a compound term whose argument is not a list:
?- open('raw250-split1.pl', read, Stream), read(Stream,train_xs(TrainXs)).
Stream = <stream>(0x7f8975e08e90),
TrainXs = parse(which.(rivers.(run.(through.(states.(bordering.(... . ...)))))), answer(_94, (river(_94), traverse(_94, _100), next_to(_100, _106), const(_106, stateid('new mexico'))))).[].(parse(what.((is).(the.(highest.(point.(... . ...))))), answer(_206, (high_point(_204, _206), const(_204, stateid(montana))))).[].(parse(what.((is).(the.(most.(... . ...)))), answer(_298, largest(_300, (population(_298, _300), state(...), ..., ...)))).[].(parse(through.(which.(states.(... . ...))), answer(_414, (state(_414), const(..., ...), traverse(..., ...)))).[].(parse(what.((is).(... . ...)), answer(_500, longest(_500, river(...)))).[].(parse(how.(... . ...), answer(_566, (..., ...))).[].(parse(... . ..., answer(..., ...)).[].(parse(..., ...).[].(... . ... .(... . ...))))))))).
YAP still uses the ./2 functor for lists, which explains why it can handle it. A workaround for SWI-Prolog is to start it with the --traditional command-line option:
$ swipl --traditional
...
?- open('raw250-split1.pl', read, Stream), read(Stream,train_xs(TrainXs)).
Stream = <stream>(0x7faeb2f77700),
TrainXs = [[parse([which, rivers, run, through, states, bordering|...], answer(_94, (river(_94), traverse(_94, _100), next_to(_100, _106), const(_106, stateid('new mexico')))))], [parse([what, is, the, highest, point|...], answer(_206, (high_point(_204, _206), const(_204, stateid(montana)))))], [parse([what, is, the, most|...], answer(_298, largest(_300, (population(_298, _300), state(...), ..., ...))))], [parse([through, which, states|...], answer(_414, (state(_414), const(..., ...), traverse(..., ...))))], [parse([what, is|...], answer(_500, longest(_500, river(...))))], [parse([how|...], answer(_566, (..., ...)))], [parse([...|...], answer(..., ...))], [parse(..., ...)], [...]|...].
The type error you get is due to the length/2 expecting a list when the first argument is bound.

There is a tilde as last character in that file, causing the syntax being invalid, so you should remove it before reading. I don't know why YAP accept the file as valid, should raise an error AFAIK.

There is a read option dotlists/2 in SWI-Prolog:
dotlists(Bool)
If true (default false), read .(a,[]) as a
list, even if lists are internally nor constructed
using the dot as functor. This is primarily intended
to read the output from write_canonical/1 from
other Prolog systems. See section 5.1.
http://www.swi-prolog.org/pldoc/man?predicate=read_term/2
This gives you the desired result, without changing the mode:
Welcome to SWI-Prolog (threaded, 64 bits, version 8.1.0)
?- read_term(X, [dotlists(true)]).
|: .(a,.(b,.(c,[]))).
X = [a, b, c].

Emacs executes `c-mode-hook` twice

Here's my emacs config
(require 'cc-mode)
(defun ffy-c-mode-hook ()
"This is settings for the C/C++ mode"
(message "ffy-c-mode-hook executed")
(electric-pair-mode +1)
(electric-indent-local-mode +1)
(if electric-indent-mode
(let ((binding (key-binding (kbd "RET"))))
(local-set-key (kbd "RET") (key-binding (kbd "C-j")))
(local-set-key (kbd "C-j") binding)))
(c-toggle-hungry-state +1)
(c-set-style "gnu")
(setq c-basic-offset 4))
(add-hook 'c-mode-hook #'ffy-c-mode-hook)
Apparently c-mode-hook is executed twice, because when I open a C file I see:
user-error: Beginning of history; no preceding item
ffy-c-mode-hook executed [2 times]
Is it a feature or a bug ? No other hooks are executed multiple times AFAIK. Plus it seems that now I can't toggle features in the hook.
I looked at the variable c-mode-hook and it its value is (ffy-c-mode-hook)
The versions of Emacs and CC-mode are
GNU Emacs 24.5.1 (i686-pc-mingw32) of 2015-04-11 on LEG570
Using CC Mode version 5.32.5
Stacktrace on ffy-c-mode-hook
ffy-c-mode-hook()
run-hooks(change-major-mode-after-body-hook prog-mode-hook c-mode-common-hook c-mode-hook c-mode-hook)
apply(run-hooks (change-major-mode-after-body-hook prog-mode-hook c-mode-common-hook c-mode-hook c-mode-hook))
run-mode-hooks(c-mode-hook)
c-mode()
set-auto-mode-0(c-mode nil)
set-auto-mode()

Following my comment about the bug report http://debbugs.gnu.org/cgi/bugreport.cgi?bug=16759 I don't think that language hooks are guaranteed to be executed once for a number of language modes. I suspect the issue is due to using define-derived-mode which is a lisp macro for defining a mode that already includes calls to hooks, this means the hooks called in the mode will be an additional execution.
You might want to try the initialization hook. The manual says:
Variable: c-initialization-hook
Hook run only once per Emacs session, when CC Mode is initialized. This is a good place to change
key bindings (or add new ones) in any of the CC Mode key maps. See
Sample Init File.
The sample it gives is here: https://www.gnu.org/software/emacs/manual/html_node/ccmode/Sample-Init-File.html#Sample-Init-File

monitoring file changes in racket (like tail -f)

I would like to implement a "tail -f" like behavior in Racket. That is, I would like to read from a file, and when I hit the end, be able making something like a "blocking" (read-line file), that shall return when some other process appends a line to file.
I tried synchronizing with (read-line-evt file) but, if I am at the end of file, instead of blocking until other data is available, it returns immediately.
Is there a way to do it?

I don't think that you have any way to avoid polling the file.
Note that all of Racket's input functions consider eof a value that should be returned when it reaches the end of the input stream -- so all of the events immediately return that when the end is reached. At least I don't see anything that looks like a "wait until some input is ready, not eof".
In any case, you also have the ffi, if you know about some system call that triggers a callback instead of polling the file. AFAICT, the linux source code for tail uses inotify, so you might be able to use an old package that interfaces that from racket called mzfam. (But it's pretty old and might need some update work.)

I don't know when Racket added file system change events, but I suspect it was since this question was asked many years ago. Now you can wait on such an event and see if you can read another line (It's not fine grained enough to tell specifically that more data was appended to the file, just that something changed about it.)
An example of a basic tail -f like program to demonstrate file-system-change-evt:
;;; tail.rkt
#lang racket/base
(require racket/list racket/port)
;;; Some utility functions and macros
;; Like take but return the list if it's less than n elements long
;; instead of raising an error
(define (take* list n)
(with-handlers ([exn:fail:contract? (lambda (e) list)])
(take list n)))
;; Repeat body forever until a break is received
(define-syntax-rule (forever body ...)
(with-handlers ([exn:break? (lambda (e) (void))])
(let loop ()
body ...
(loop))))
;; Display the last N lines of a file. Could be more efficient, but
;; this part's not the point...
(define (display-last-lines port n)
(for-each displayln
(reverse
(for/fold ([lines '()])
([line (in-lines port)])
(take* (cons line lines) n)))))
;; Wait for the file's status to change and try to read lines when it does.
(define (follow-tail file)
(call-with-input-file file
(lambda (port)
(display-last-lines port 10)
(forever
(sync (filesystem-change-evt file))
(for ([line (in-lines port)])
(displayln line))))))
(module+ main
(unless (= (vector-length (current-command-line-arguments)) 1)
(displayln "Usage: racket tail.rkt FILENAME" (current-error-port))
(exit 1))
(follow-tail (string->path (vector-ref (current-command-line-arguments) 0))))
After being inspired by this question and Eli's mention of inotify in his answer, and seeing that there still wasn't a Racket package to provide access to it (I think the standard file system change code uses it internally, but it's not exposed at any low level to users), I wrote it myself. A version of the core tail function from above using it:
(require inotify)
(define (follow-tail file)
(call-with-input-file file
(lambda (port)
(display-last-lines port 10)
(call-with-inotify-instance
`((,file (IN_MODIFY)))
(lambda (inotify wds)
(forever
(sync inotify)
(for ([line (in-lines port)])
(displayln line))))))))

How do you use Ruby/DL? Is this right?

I am trying to write an interface between RSPEC (ruby flavoured BDD) and a Windows application. The application itself is written in an obscure language, but it has a C API to provide access. I've gone with Ruby/DL but am having difficulties getting even the most basic call to a DLL method to work. Here is what I have so far, in a file called gt4r.rb:
require 'dl/import'
module Gt4r
extend DL::Importable
dlload 'c:\\gtdev\\r321\\bin\\gtvapi'
# GTD initialization/termination functions
extern 'int GTD_init(char *[], char *, char *)'
extern 'int GTD_initialize(char *, char *, char *)'
extern 'int GTD_done(void)'
extern 'int GTD_get_error_message(int, char **)'
end
My reading so far suggests that this is all I need to get going, so I wrote up a RSPEC example:
require 'gt4r'
##test_environment = "INCLUDE=C:\\graphtalk\\env\\aiadev\\config\\aiadev.ini"
##normal_user = "BMCHARGUE"
describe Gt4r do
it 'initializes' do
rv = Gt4r.gTD_initialize ##normal_user, ##normal_user, ##test_environment
rv.should == 0
end
end
And when run...
C:\code\GraphTalk>spec -fs -rgt4r gt4r_spec.rb
Gt4r
- initializes (FAILED - 1)
1)
'Gt4r initializes' FAILED
expected: 0,
got: 13 (using ==)
./gt4r_spec.rb:9:
Finished in 0.031 seconds
1 example, 1 failure
The return value (13) is an actual return code, meaning an error, but when I try to add the gTD_get_error_message call to my RSPEC, I can't get the parameters to work.
Am I heading in the right direction and can anyone point to the next thing I can try?
Thanks,
Brett
A follow up to this question, showing the part that fails when I try to get the error message from my target library:
require 'gt4r'
##test_environment = "INCLUDE=C:\\graphtalk\\env\\aiadev\\config\\aiadev.ini"
##normal_user = "BMCHARGUE"
describe Gt4r do
it 'initializes' do
rv = Gt4r.gTD_initialize ##normal_user, ##normal_user, ##test_environment
Gt4r.gTD_get_error_message rv, #msg
#msg.should == ""
rv.should == 0
end
end
I expect the error message to be returned in #msg, but when run I get the following:
Gt4r
(eval):5: [BUG] Segmentation fault
ruby 1.8.6 (2008-08-11) [i386-mswin32]
This application has requested the Runtime to terminate it in an unusual way.
Please contact the application's support team for more information.
And this if I use a symbol (:msg) instead:
C:\code\GraphTalk\gt4r_dl>spec -fs -rgt4r gt4r_spec.rb
Gt4r
- initializes (ERROR - 1)
1)
NoMethodError in 'Gt4r initializes'
undefined method `to_ptr' for :msg:Symbol
(eval):5:in `call'
(eval):5:in `gTD_get_error_message'
./gt4r_spec.rb:9:
Finished in 0.046 seconds
1 example, 1 failure
Clearly I am missing something about passing parameters between ruby and C, but what?

The general consensus is you want to avoid DL as much as possible. The (english) documentation is quite sketchy and the interface is difficult to use for anything but trivial examples.
Ruby native C interface is MUCH easier to program against. Or you could use FFI, which fills a similiar niche to DL, originally comes from the rubinius project and has recently been ported to "normal" ruby. It has a nicer interface and is much less painful to use:
http://blog.headius.com/2008/10/ffi-for-ruby-now-available.html

The return value (13) is an actual
return code, meaning an error, but
when I try to add the
gTD_get_error_message call to my
RSPEC, I can't get the parameters to
work.
It might help posting the error instead of the code that worked :)
Basically, once you start having to deal with pointers as in (int, char **), things get ugly.

You need to allocate the data pointer for msg to be written to, since otherise C will have nowhere to write the error messages. Use DL.mallo.

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