can't use Racket's better-monads library - functional-programming

I'm trying to make use of Racket's better-monads library.
I have the following program :
(module bmonads racket
(provide add)
(require functional/better-monads)
(define (add)
(mlet* ((x 10)
(y 11))
(+ x y))))
When I try to load this file into the REPL(geiser), I get the following error message :
Welcome to Racket v5.3.4.
racket#> (require (file "bmonads.rkt"))
bmonads.rkt:4:11: functional/better-monads: standard-module-name-resolver: collection not found
collection: "functional"
in collection directories:
/home/me/.racket/5.3.4/collects
/usr/share/racket/collects
/home/me/.emacs.d/geiser-0.5/scheme/racket/
in: functional/better-monads
context...:
standard-module-name-resolver
standard-module-name-resolver
/usr/share/racket/collects/racket/private/misc.rkt:87:7
racket#>

Because better-monads is part of the PLT package functional.plt, you will need to load it via PlaneT.
(require (planet "better-monads.rkt" ("toups" "functional.plt" 1 1)))
Specific documentation for loading the library: http://planet.racket-lang.org/display.ss?package=functional.plt&owner=toups
General documentation on PlaneT: http://docs.racket-lang.org/planet/Using_PLaneT.html?q=planeT&q=monand

Related

How to set iolib timeout

I'm using IOLIB with this code to resolve a hostname:
(sockets:address-to-string (sockets:lookup-hostname name))
I works, but the functions does not take any timeout paramenter, and i cannot figure out how to set these using socket options.
Unfortunately this is not easy to find (in particular, this is not documented), but following the chain of calls from lookup-hostname (M-. in Emacs), you can see your code eventually calls dns-query:
(defun dns-query (name &key (type :a) (search *dns-search-domain*)
(nameservers *dns-nameservers*) decode
(repeat *dns-repeat*) (timeout *dns-timeout*))
...)
The timeout argument defaults to a special variable iolib/sockets::*dns-timeout*, which is globally bound to 10. You then only need to bind it around your code to set a different timeout:
(let ((iolib/sockets::*dns-timeout* 1))
...)
The variable is not exported, but dns-query is, maybe it is better to call that function directly.
CL-USER> (iolib:dns-query "http://example.com" :timeout 0.0001)
NIL
CL-USER> (iolib:dns-query "http://example.com" :timeout 1)
#<DNS RESPONSE Id: 61273, Question: #(#<"http://example.com." A IN>) Flags: :OP/S :RD :RA :NAME-ERROR, Sections: QD(1) AN(0) NS(1) AD(0)>

How to search for files with a wildcard in Common Lisp?

I am not satisfied to find files matching a string like this:
(remove-if-not (lambda (it)
(search "wildcard" (namestring it)))
(uiop:directory-files "./"))
;; I'll ignore case with str:contains?
;; https://github.com/vindarel/cl-str
How would one search for files with unix-style wildcards ?
If it is not built-in, I'd enjoy a solution with uiop. Maybe there is with Osicat or cl-fad (with which it doesn't seem so, the documentation oftentimes says "non-wild pathname").
Bonus if it is possible to use the double wildcard to traverse directories recursively (./**/*.jpg).
edit: I have tried variants of (directory #p"./**/*.jpg") and it returns nil :( Also tried #p".*jpg", #p"./.*jpg",…
(wild-pathname-p (pathname "*.jpg"))
(:WILD :WILD-INFERIORS)
(make-pathname :name :wild :type "jpg")
#P"*.jpg"
The following gets me files by jpg extension, but it isn't a proper wildcard yet:
(directory *)
(#P"/home/vince/cl-cookbook/AppendixA.jpg"
#P"/home/vince/cl-cookbook/AppendixB.jpg"
#P"/home/vince/cl-cookbook/AppendixC.jpg")
Documentation on pathnames and make-pathname: http://gigamonkeys.com/book/files-and-file-io.html (no mentions of wildcards)
SBCL
SBCL supports wildcards in names. First, create some files:
(loop
with stem = #P"/tmp/stack/_.txt"
initially (ensure-directories-exist stem)
for name in '("abc" "def" "cadar" "cdadr" "cddr")
for path = (make-pathname :name name :defaults stem)
do (open path :direction :probe :if-does-not-exist :create))
Then, list all files that contains an "a":
CL-USER> (directory #P"/tmp/stack/*a*.txt")
(#P"/tmp/stack/abc.txt" #P"/tmp/stack/cadar.txt" #P"/tmp/stack/cdadr.txt")
The pathname contains an implementation-specific (valid) name component:
CL-USER> (describe #P"/tmp/stack/*a*.txt")
#P"/tmp/stack/*a*.txt"
[structure-object]
Slots with :INSTANCE allocation:
HOST = #<SB-IMPL::UNIX-HOST {10000F3FF3}>
DEVICE = NIL
DIRECTORY = (:ABSOLUTE "tmp" "stack")
NAME = #<SB-IMPL::PATTERN :MULTI-CHAR-WILD "a" :MULTI-CHAR-WILD>
TYPE = "txt"
VERSION = :NEWEST
; No value
SBCL also defines sb-ext:map-directory, which process files one by one, instead of first collecting all files in a list.
Portable solutions
If you need to stick to standard pathname components, you can first call directory with normal wildcards, and filter the resulting list:
CL-USER> (remove-if-not (wildcard "*a*")
(directory #P"/tmp/stack/*.txt")
:key #'pathname-name)
(#P"/tmp/stack/abc.txt" #P"/tmp/stack/cadar.txt" #P"/tmp/stack/cdadr.txt")
... where wildcard might be based on regex (PPCRE):
(defun parse-wildcard (string)
(delete ""
(map 'list
(lambda (string)
(or (cdr (assoc string
'(("*" . :wild)
("?" . :char))
:test #'string=))
string))
(ppcre:split '(:sequence
(:negative-lookbehind #\\)
(:register (:alternation #\* #\?)))
string
:with-registers-p t))
:test #'string=))
(note: the above negative lookbehind does not eliminate escaped backslashes)
(defun wildcard-regex (wildcard)
`(:sequence
:start-anchor
,#(loop
for token in wildcard
collect (case token
(:char :everything)
(:wild '(:greedy-repetition 0 nil :everything))
(t token)))
:end-anchor))
(defun wildcard (string)
(let ((scanner (ppcre:create-scanner
(wildcard-regex (parse-wildcard string)))))
(lambda (string)
(ppcre:scan scanner string))))
Intermediate functions:
CL-USER> (parse-wildcard "*a*a\\*a?\\?a")
(:WILD "a" :WILD "a\\*a" :CHAR "\\?a")
CL-USER> (wildcard-regex (parse-wildcard "*a*a\\*a?\\?a"))
(:SEQUENCE :START-ANCHOR #1=(:GREEDY-REPETITION 0 NIL :EVERYTHING) "a" #1# "a\\*a" :EVERYTHING "\\?a" :END-ANCHOR)
no current directory and no home directory characters
The concept of . denoting the current directory does not exist in portable Common Lisp. This may exist in specific filesystems and specific implementations.
Also ~ to denote the home directory does not exist. They may be recognized by some implementations as non-portable extensions.
In pathname strings you have * and ** as wildcards. This works in absolute and relative pathnames.
defaults for the default pathname
Common Lisp has *default-pathname-defaults* which provides a default for some pathname operations.
Examples
CL-USER 46 > (directory "/bin/*")
(#P"/bin/[" #P"/bin/bash" #P"/bin/cat" .... )
Now in above it is already slightly undefined or diverging what implementations do on Unix:
resolve symbolic links?
include 'hidden' files?
include files with types?
Next:
CL-USER 47 > (directory "/bin/*sh")
(#P"/bin/zsh" #P"/bin/tcsh" #P"/bin/sh" #P"/bin/ksh" #P"/bin/csh" #P"/bin/bash")
Using a relative pathname:
CL-USER 48 > (let ((*default-pathname-defaults* (pathname "/bin/")))
(directory "*sh"))
(#P"/bin/zsh" #P"/bin/tcsh" #P"/bin/sh" #P"/bin/ksh" #P"/bin/csh" #P"/bin/bash")
Files in your home directory:
CL-USER 49 > (let ((*default-pathname-defaults* (user-homedir-pathname)))
(directory "*"))
The same:
CL-USER 54 > (directory (make-pathname :name "*"
:defaults (user-homedir-pathname)))
Finding all files ending with sh in /usr/local/ and below:
CL-USER 54 > (directory "/usr/local/**/*sh")
Constructing pathnames with MAKE-PATHNAME
Three ways to find all .h files under /usr/local/:
(directory "/usr/local/**/*.h")
(directory (make-pathname :name :wild
:type "h"
:defaults "/usr/local/**/")
(directory
(make-pathname :name :wild
:type "h"
:directory '(:ABSOLUTE "usr" "local" :WILD-INFERIORS)))
Problems
There are a lot of different interpretations of implementations across platforms ('windows', 'unix', 'mac', ...) and even on the same platform (especially 'windows' or 'unix'). Stuff like unicode in pathnames creates additional complexity - not describe in the CL standard.
We still have a lot of different filesystems ( https://en.wikipedia.org/wiki/List_of_file_systems ), but they are different or different in capabilities from what was typical when Common Lisp was designed. Implementations may have tracked the changes, but not necessarily in portable ways.

How to use Clozure CL on IPv6 only network?

I've tried to replace SBCL with Clozure CL when working in IPv6 only network, but encountered an error like that:
MIGRATIONS> (ignore-errors (ccl:make-socket :remote-host "ya.ru" :remote-port 443))
NIL
#<CCL:NO-APPLICABLE-METHOD-EXISTS #x302005215E5D>
MIGRATIONS> (ignore-errors (ccl:make-socket :remote-host "ya.ru" :remote-port 443 :address-family :internet))
NIL
#<CCL:NO-APPLICABLE-METHOD-EXISTS #x3020052549AD>
MIGRATIONS> (ignore-errors (ccl:make-socket :remote-host "ya.ru" :remote-port 443 :address-family :internet6))
#<BASIC-TCP-STREAM ISO-8859-1 (SOCKET/16) #x3020051D4A9D>
The problem is that many libraries when using CCL:MAKE-TCP-SOCKET don't specify address-family or specify an :internet.
Is there is a way to patch ccl:make-socket at runtime to override this setting?
Advise a function
Several implementations of Common Lisp allow advising (-> patching) of normal functions. Advising is a non-standard feature and different implementations provide it in slightly different ways. A related mechanism is standardized for CLOS generic functions with :before, :after and :around methods.
The purpose is to add one or more patches to a function, after it has been defined and without altering the original source code.
Typically this requires that the function call to this function is not inlined.
The macro ADVISE in Clozure Common Lisp
Patching functions in Clozure CL can be done with the macro ADVISE. See the documentation for advising.
Let's say we have a function FOOBAR:
? (defun foobar (a b &key c (d :foobar)) (list a b c d))
FOOBAR
FOOBAR gets called inside TEST:
? (defun test (a) (foobar a 20 :c 30))
TEST
? (test 10)
(10 20 30 :FOOBAR)
We now want to patch FOOBAR such that named arg :D gets called with a different value.
We change the arglist to insert the new named argument after the two required args:
? (advise foobar (let ((arglist (list* (first arglist)
(second arglist)
:d :ipv6
(cddr arglist))))
(:do-it)) ; calling the original function
:when :around ; advise around it
:name :ipv6) ; the name of this advise
#<Compiled-function (CCL::ADVISED 'FOOBAR) (Non-Global) #x3020010D1CCF>
Now we can call our TEST function and it will call the advised function FOOBAR.
? (test 10)
(10 20 30 :IPV6)
Advise for CCL:MAKE-SOCKET
You could write a similar advise for CCL:MAKE-SOCKET.
Untested:
(advise ccl:make-socket (let ((arglist (list* :address-family
:internet6
arglist)))
(:do-it))
:when :around
:name :internet6)
This can be done!
First make a copy of the original make-socket
(IN-PACKAGE :ccl)
(DEFPARAMETER original-make-socket #'make-socket)
Then redefine make-socket. Note: You will have to provide the full spec for all keyword parameters. As it is, I've used only the ones from your question for demonstration.
(defun make-socket (&key (remote-host "defau.lt")
(remote-port 443)
(address-family :internet6))
(declare (ignore address-family))
(format t "Calling new make-socket with address-family as internet6!")
(funcall original-make-socket
:remote-host remote-host
:remote-port remote-port
:address-family :internet6))
This will signal a continuable error.
Type :go at the repl to continue.
This will successfully patch make-socket.
Now any calls to make-socket will be to the new definition. Try:
(IN-PACKAGE :cl-user)
(ccl:make-socket :remote-host "ya.ru" :remote-port 443 :address-family :IRRELEVANT)
Another way to do it, would be to override the global variable *warn-if-redefine-kernel* before redefining make-socket.
(setf *warn-if-redefine-kernel* nil)
This will avoid the continuable error signal, and straight patch the kernel function.

How to integrate flowtype with spacemacs

I'm spacemacs fan. I want to use Facebook Flow but I have not idea how to integrate it with spacemacs. I'm using flow with nuclide but I need to relearn everything to be productive. There is this script on flow repository to use it with emacs. I need a guide for how to use it within spacemacs.
Thanks.
I used Bodil's flow flycheck config here: https://github.com/bodil/emacs.d/blob/d28264cf072bb8a62459a48813d0cb30804b4f5b/bodil/bodil-js.el#L121-L154
I made it work with spacemacs's react-mode and default eslint flychecker by adding the following to my dotspacemacs/user-config (https://github.com/saltycrane/.spacemacs.d/blob/9d985ace9251529c2b8d7857e2ec9835b103084c/init.el#L383-L414):
;; Flow (JS) flycheck config (http://flowtype.org)
;; from https://github.com/bodil/emacs.d/blob/master/bodil/bodil-js.el
(require 'f)
(require 'json)
(require 'flycheck)
(defun flycheck-parse-flow (output checker buffer)
(let ((json-array-type 'list))
(let ((o (json-read-from-string output)))
(mapcar #'(lambda (errp)
(let ((err (cadr (assoc 'message errp))))
(flycheck-error-new
:line (cdr (assoc 'line err))
:column (cdr (assoc 'start err))
:level 'error
:message (cdr (assoc 'descr err))
:filename (f-relative
(cdr (assoc 'path err))
(f-dirname (file-truename
(buffer-file-name))))
:buffer buffer
:checker checker)))
(cdr (assoc 'errors o))))))
(flycheck-define-checker javascript-flow
"Javascript type checking using Flow."
:command ("flow" "--json" source-original)
:error-parser flycheck-parse-flow
:modes react-mode
:next-checkers ((error . javascript-eslint))
)
(add-to-list 'flycheck-checkers 'javascript-flow)
Also be sure the Flow command line tool is installed. Install it like this:
npm install -g flow-bin
I think Bodil intended to make the messages short, but I would like to have flycheck display more verbose messages. If anyone knows how to do that, I'd appreciate it.
EDIT 2016-08-12: the original version I posted gave a Symbol's function definition is void: flycheck-define-checker error on initial load. I updated the code above to add a require 'flycheck to get rid of that error.
The answer by saltycrane worked fine for me. Thanks! The solution gives a very short error messages as he points out. I have improved the error messages to be more verbose and look more like the output from flow cli output.
A note to new users who wants to use this script is to make sure you edit it to use the correct mode in flycheck-define-checker at the bottom. I use this in js2-mode, and saltycrane uses react-mode. Edit it to use whatever you are using.
(require 'f)
(require 'json)
(require 'flycheck)
(defun flycheck-parse-flow (output checker buffer)
(let ((json-array-type 'list))
(let ((o (json-read-from-string output)))
(mapcar #'(lambda (errp)
(let ((err (cadr (assoc 'message errp)))
(err2 (cadr (cdr (assoc 'message errp)))))
(flycheck-error-new
:line (cdr (assoc 'line err))
:column (cdr (assoc 'start err))
:level 'error
:message (concat (cdr (assoc 'descr err)) ". " (cdr (assoc 'descr err2)))
:filename (f-relative
(cdr (assoc 'path err))
(f-dirname (file-truename
(buffer-file-name))))
:buffer buffer
:checker checker)))
(cdr (assoc 'errors o))))))
(flycheck-define-checker javascript-flow
"Static type checking using Flow."
:command ("flow" "--json" source-original)
:error-parser flycheck-parse-flow
:modes js2-mode)
(add-to-list 'flycheck-checkers 'javascript-flow)

Does a Clojure proxy always invoke super.method()?

While using Clojure proxies, fns passed to proxy should override existing methods or are they called in conjunction with super.method()?
In the following code, RequestHandler.get() is invoked along with the proxy get [].
;see: http://github.com/paulosuzart/JTornado
(ns org.ctornadoweb)
(import '(org.jtornadoweb Web$RequestHandler))
(import '(org.jtornadoweb HttpServer Web$Application))
(let [myHandler (proxy [Web$RequestHandler] []
(get []
(.write "Hi CLJ"))
(post []
(.write "POST")))]
(.listen
(HttpServer.
(.add (Web$Application.) "/" (class myHandler))
false nil false) 8089))
The same happens to the compiled/inheritance version:
; Starts a JTornado HTTP Server and a sample RequestHandler.
; Bit verbose due to compilation directives. Recommendation is to generate
; a set of macros to hide this.
(ns org.ctornadoweb
; Compiled and implements a static main method to start the server
(:import (org.jtornadoweb HttpServer)
(org.jtornadoweb.Web$Application)
(org.jtornadoweb.Web$RequestHandler))
(:gen-class :prefix "server-"))
(gen-class
:name org.ctornadoweb.MyHandler
:extends org.jtornadoweb.Web$RequestHandler
:prefix "do")
(defn do-get [this]
"Handles the HTTP GET method"
(.write "hello clojure"))
(defn do-post [this]
"Handles the HTTP POST method"
(.write (.getArgument "name" "default" false)))
(defn server-main []
"main method"
(.listen
(org.jtornadoweb.HttpServer.
(.add (org.jtornadoweb.Web$Application.) "/" org.ctornadoweb.MyHandler)
false nil false) 8089))
;use (compile 'org.ctornadoweb)
The trace shows the proxy get being invoked and then the super.get, what throws (by default) an exception.
HTTP 405: Method Not Allowed
at org.jtornadoweb.Web$RequestHandler.get(Web.java:72)
at org.ctornadoweb.proxy$org.jtornadoweb.Web$RequestHandler$0.get(Unknown Source)
I tried to find some words about the actual behavior of Clojure Proxies. Can someone give this help?
No, the super method will not be called automatically, though you can explicitly call it with proxy-super.
The following test case shows things working as they should:
user=> (def foo
(proxy [java.util.ArrayList] []
(clear [] (println "not clearing"))))
#'user/foo
user=> (.size foo)
0
user=> (.add foo "hi")
true
user=> (.add foo "bye")
true
user=> (.size foo)
2
user=> (.clear foo)
not clearing
nil
user=> (.size foo)
2
If super.clear() were getting called, the size would show as 0.

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