Re: What is this notation? "-a"
https://stackoverflow.com/questions/10846423/is-there-a-clojure-convention-for-naming-private-functions/10853372 On Saturday, December 25, 2021 at 6:53:56 PM UTC-5 hank@gmail.com wrote: > Hello -- > > Sometimes I see a notation that uses a prefix "-", as in: > > user> (def -a (atom [])) > #'user/-a > > Is there a special meaning/convention regarding this use of a hyphen > prefix? > TIA > -- Hank > > -- You received this message because you are subscribed to the Google Groups "Clojure" group. To post to this group, send email to clojure@googlegroups.com Note that posts from new members are moderated - please be patient with your first post. To unsubscribe from this group, send email to clojure+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/clojure?hl=en --- You received this message because you are subscribed to the Google Groups "Clojure" group. To unsubscribe from this group and stop receiving emails from it, send an email to clojure+unsubscr...@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/clojure/dd81c045-f6a3-4c31-94ea-1f252e0fa86an%40googlegroups.com.
Re: Pesky java interop bug with 0xFFFFFFF error in BuferredReader
Hank,
Just a message to give you the solution [spoiler alert]
Don't read it, if you still want to search :)
SPOILER
SPOILER
;; ugly version using the fact that java objects are mutable in place
(defn ugly-read-chars-one-by-one
[reader]
(let [sb (StringBuilder.)]
(loop []
(let [v (.read reader)]
(if (neg? v)
(.toString sb)
(do (.append sb (char v))
(recur)))
;; "better" version using loop bindings
(defn read-chars-one-by-one
[reader]
(loop [sb (StringBuilder.)
v (.read reader)]
(if (neg? v)
(.toString sb)
(recur (.append sb (char v))
(.read reader)
;; usage
(require '[clojure.java.io :as io])
(with-open [rdr (io/reader "some-file.txt")]
(read-chars-one-by-one rdr))
Regards,
Laurent
Le dimanche 26 décembre 2021 à 18:12:56 UTC+1, hank@gmail.com a écrit :
> Hi --
> Thanks for taking the time to help me.
> As far as I understand the examples, loop has this template:
>
> loop [binding]
> (condition
> (statement)
> (recur (binding)))
> And in 'recur' the loop is re-executed with new bindings.
>
> There was indeed an issue with the 'recur' outside 'when'. Thanks for
> pointing that out.
> I corrected that in the version below.
>
> I also changed to a smaller file (UTF-8 encoded in Linux), called
> 'ribs.txt', with the following content:
>
> source/txt on master [!?]
> ❯ cat ribs.txt
> Try my delicious pork-chop ribs!
>
> source/txt on master [!?]
> ❯ cat ribs.hexdump
> : 54 72 79 20 6d 79 20 64 65 6c 69 63 69 6f 75 73 Try my delicious
> 0010: 20 70 6f 72 6b 2d 63 68 6f 70 20 72 69 62 73 21 pork-chop ribs!
> 0020: 0a .
>
>
> (defn pt8 [file]
>(let [afr (FileReader. file); instances of FileReader, BufferedReader,
> StringBuffer
> bfr (BufferedReader. afr)
> ct (StringBuilder.)
> this-list (list afr bfr ct)]
> ; (apply println this-list)
> ; put recur INSIDE THE WHEN
> (loop [val (.read bfr)]
>(when (not (= val -1))
> (.append ct (Character/toChars (.read bfr)))
>(recur [val (.read bfr)])))
> ; when finished...
> (.toString ct)))
>
> I think this fixed the 'recur', because it does rebinding to a new call to
> "read()".
> However, the errors remains.
>
> user> (pt8 ribs)
> Execution error (IllegalArgumentException) at java.lang.Character/toChars
> (Character.java:8572).
> Not a valid Unicode code point: 0x
>
> The file used is sufficiently small so that we can walk the bytes using
> jshell:
>
> jshell> FileReader afr = new FileReader("/home/hank/source/txt/ribs.txt/")
> afr ==> java.io.FileReader@1698c449
>
> jshell> BufferedReader bfr = new BufferedReader(afr)
> bfr ==> java.io.BufferedReader@5ef04b5
>
> jshell> StringBuilder ct = new StringBuilder()
> ct ==>
>
> FileReader reads 2 bytes per character so, to get to the end, of the first
> hexdump line, let's walk 32 bytes:
>
> jshell> for (int i=0; i < 31; i++) {
>...> if ((value = bfr.read()) != -1) { ct.append((char) value); }
>...> i++;
>...> }
>
> jshell> ct
> ct ==> Try my delicious
>
> : 54 72 79 20 6d 79 20 64 65 6c 69 63 69 6f 75 73 Try my delicious
> T r y SP m y SP d e l i c i o u s (< YOU ARE
> HERE)
>
> : 54 72 79 20 6d 79 20 64 65 6c 69 63 69 6f 75 73 Try my delicious
> 0010: 20 70 6f 72 6b 2d 63 68 6f 70 20 72 69 62 73 21 pork-chop ribs!
> 0020: 0a .
>
> Now we iterate 31 more bytes, stopping short of the last character:
> jshell> for (int i=0; i < 30; i++) {
>...> if ((value = bfr.read()) != -1) { ct.append((char) value); }
>...> i++;
>...> }
>
> jshell> ct
> ct ==> Try my delicious pork-chop ribs
>
> : 54 72 79 20 6d 79 20 64 65 6c 69 63 69 6f 75 73 Try my delicious
> 0010: 20 70 6f 72 6b 2d 63 68 6f 70 20 72 69 62 73 21 pork-chop ribs!
> ^ we stopped here
>
> We just advance one more:
>
> jshell> if ((value = bfr.read()) != -1) { ct.append((char) value); }
>...>
>
> jshell> ct
> ct ==> Try my delicious pork-chop ribs!
>
> And one more time, to see if it borks:
> jshell> if ((value = bfr.read()) != -1) { ct.append((char) value); }
>
> jshell> ct
> ct ==> Try my delicious pork-chop ribs!
>
> Nope, everything looks fine. Now where does that '0xFFF" come from?!
> -- Hank
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Re: Pesky java interop bug with 0xFFFFFFF error in BuferredReader
Hi Hank,
That loop/recur is still wrong because `loop` set bindings to define names
and gives initial values but `recur` does *not set bindings*, it just
provides new values.
So `recur` does not need a vector of bindings like `loop`
The pattern is as follow:
(loop [a-local-var "initial-value"]
(if (should-stop-looping? a-local-var)
(execute-last-expression a-local-var)
(recur a-new-local-var)))
In your pt8 function, you are reading your stream to many times in a loop,
if I write your pt8 function in procedural pseudo-code, this is what I get:
bfr = input-stream()
ct = string-buffer()
set loop-start // set loop point
with val, // set loop args
val = read(bfr) // set args initial value, first read
if !(val == -1) {
ct.append(char(read(bfr))) // read again! and lose previous byte!!
goto loop-start
with val = vector(val, read(bfr)) // read again! this byte will
be lost soon :(
}
ct.toString()
Regards,
Laurent
Le dimanche 26 décembre 2021 à 18:12:56 UTC+1, hank@gmail.com a écrit :
> Hi --
> Thanks for taking the time to help me.
> As far as I understand the examples, loop has this template:
>
> loop [binding]
> (condition
> (statement)
> (recur (binding)))
> And in 'recur' the loop is re-executed with new bindings.
>
> There was indeed an issue with the 'recur' outside 'when'. Thanks for
> pointing that out.
> I corrected that in the version below.
>
> I also changed to a smaller file (UTF-8 encoded in Linux), called
> 'ribs.txt', with the following content:
>
> source/txt on master [!?]
> ❯ cat ribs.txt
> Try my delicious pork-chop ribs!
>
> source/txt on master [!?]
> ❯ cat ribs.hexdump
> : 54 72 79 20 6d 79 20 64 65 6c 69 63 69 6f 75 73 Try my delicious
> 0010: 20 70 6f 72 6b 2d 63 68 6f 70 20 72 69 62 73 21 pork-chop ribs!
> 0020: 0a .
>
>
> (defn pt8 [file]
>(let [afr (FileReader. file); instances of FileReader, BufferedReader,
> StringBuffer
> bfr (BufferedReader. afr)
> ct (StringBuilder.)
> this-list (list afr bfr ct)]
> ; (apply println this-list)
> ; put recur INSIDE THE WHEN
> (loop [val (.read bfr)]
>(when (not (= val -1))
> (.append ct (Character/toChars (.read bfr)))
>(recur [val (.read bfr)])))
> ; when finished...
> (.toString ct)))
>
> I think this fixed the 'recur', because it does rebinding to a new call to
> "read()".
> However, the errors remains.
>
> user> (pt8 ribs)
> Execution error (IllegalArgumentException) at java.lang.Character/toChars
> (Character.java:8572).
> Not a valid Unicode code point: 0x
>
> The file used is sufficiently small so that we can walk the bytes using
> jshell:
>
> jshell> FileReader afr = new FileReader("/home/hank/source/txt/ribs.txt/")
> afr ==> java.io.FileReader@1698c449
>
> jshell> BufferedReader bfr = new BufferedReader(afr)
> bfr ==> java.io.BufferedReader@5ef04b5
>
> jshell> StringBuilder ct = new StringBuilder()
> ct ==>
>
> FileReader reads 2 bytes per character so, to get to the end, of the first
> hexdump line, let's walk 32 bytes:
>
> jshell> for (int i=0; i < 31; i++) {
>...> if ((value = bfr.read()) != -1) { ct.append((char) value); }
>...> i++;
>...> }
>
> jshell> ct
> ct ==> Try my delicious
>
> : 54 72 79 20 6d 79 20 64 65 6c 69 63 69 6f 75 73 Try my delicious
> T r y SP m y SP d e l i c i o u s (< YOU ARE
> HERE)
>
> : 54 72 79 20 6d 79 20 64 65 6c 69 63 69 6f 75 73 Try my delicious
> 0010: 20 70 6f 72 6b 2d 63 68 6f 70 20 72 69 62 73 21 pork-chop ribs!
> 0020: 0a .
>
> Now we iterate 31 more bytes, stopping short of the last character:
> jshell> for (int i=0; i < 30; i++) {
>...> if ((value = bfr.read()) != -1) { ct.append((char) value); }
>...> i++;
>...> }
>
> jshell> ct
> ct ==> Try my delicious pork-chop ribs
>
> : 54 72 79 20 6d 79 20 64 65 6c 69 63 69 6f 75 73 Try my delicious
> 0010: 20 70 6f 72 6b 2d 63 68 6f 70 20 72 69 62 73 21 pork-chop ribs!
> ^ we stopped here
>
> We just advance one more:
>
> jshell> if ((value = bfr.read()) != -1) { ct.append((char) value); }
>...>
>
> jshell> ct
> ct ==> Try my delicious pork-chop ribs!
>
> And one more time, to see if it borks:
> jshell> if ((value = bfr.read()) != -1) { ct.append((char) value); }
>
> jshell> ct
> ct ==> Try my delicious pork-chop ribs!
>
> Nope, everything looks fine. Now where does that '0xFFF" come from?!
> -- Hank
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Re: Pesky java interop bug with 0xFFFFFFF error in BuferredReader
Hi --
Thanks for taking the time to help me.
As far as I understand the examples, loop has this template:
loop [binding]
(condition
(statement)
(recur (binding)))
And in 'recur' the loop is re-executed with new bindings.
There was indeed an issue with the 'recur' outside 'when'. Thanks for
pointing that out.
I corrected that in the version below.
I also changed to a smaller file (UTF-8 encoded in Linux), called
'ribs.txt', with the following content:
source/txt on master [!?]
❯ cat ribs.txt
Try my delicious pork-chop ribs!
source/txt on master [!?]
❯ cat ribs.hexdump
: 54 72 79 20 6d 79 20 64 65 6c 69 63 69 6f 75 73 Try my delicious
0010: 20 70 6f 72 6b 2d 63 68 6f 70 20 72 69 62 73 21 pork-chop ribs!
0020: 0a .
(defn pt8 [file]
(let [afr (FileReader. file); instances of FileReader, BufferedReader,
StringBuffer
bfr (BufferedReader. afr)
ct (StringBuilder.)
this-list (list afr bfr ct)]
; (apply println this-list)
; put recur INSIDE THE WHEN
(loop [val (.read bfr)]
(when (not (= val -1))
(.append ct (Character/toChars (.read bfr)))
(recur [val (.read bfr)])))
; when finished...
(.toString ct)))
I think this fixed the 'recur', because it does rebinding to a new call to
"read()".
However, the errors remains.
user> (pt8 ribs)
Execution error (IllegalArgumentException) at java.lang.Character/toChars
(Character.java:8572).
Not a valid Unicode code point: 0x
The file used is sufficiently small so that we can walk the bytes using
jshell:
jshell> FileReader afr = new FileReader("/home/hank/source/txt/ribs.txt/")
afr ==> java.io.FileReader@1698c449
jshell> BufferedReader bfr = new BufferedReader(afr)
bfr ==> java.io.BufferedReader@5ef04b5
jshell> StringBuilder ct = new StringBuilder()
ct ==>
FileReader reads 2 bytes per character so, to get to the end, of the first
hexdump line, let's walk 32 bytes:
jshell> for (int i=0; i < 31; i++) {
...> if ((value = bfr.read()) != -1) { ct.append((char) value); }
...> i++;
...> }
jshell> ct
ct ==> Try my delicious
: 54 72 79 20 6d 79 20 64 65 6c 69 63 69 6f 75 73 Try my delicious
T r y SP m y SP d e l i c i o u s (< YOU ARE
HERE)
: 54 72 79 20 6d 79 20 64 65 6c 69 63 69 6f 75 73 Try my delicious
0010: 20 70 6f 72 6b 2d 63 68 6f 70 20 72 69 62 73 21 pork-chop ribs!
0020: 0a .
Now we iterate 31 more bytes, stopping short of the last character:
jshell> for (int i=0; i < 30; i++) {
...> if ((value = bfr.read()) != -1) { ct.append((char) value); }
...> i++;
...> }
jshell> ct
ct ==> Try my delicious pork-chop ribs
: 54 72 79 20 6d 79 20 64 65 6c 69 63 69 6f 75 73 Try my delicious
0010: 20 70 6f 72 6b 2d 63 68 6f 70 20 72 69 62 73 21 pork-chop ribs!
^ we stopped here
We just advance one more:
jshell> if ((value = bfr.read()) != -1) { ct.append((char) value); }
...>
jshell> ct
ct ==> Try my delicious pork-chop ribs!
And one more time, to see if it borks:
jshell> if ((value = bfr.read()) != -1) { ct.append((char) value); }
jshell> ct
ct ==> Try my delicious pork-chop ribs!
Nope, everything looks fine. Now where does that '0xFFF" come from?!
-- Hank
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Re: Pesky java interop bug with 0xFFFFFFF error in BuferredReader
Hank Your loop/recur in your pt5 function is still not good. Take the time to read the loop/recur documentation and to understand examples. A Clojure loop/recur is not really a loop like in other procedural languages. It is more akin to a new function call at the `loop` point with new args provided by the `recur` call. If you continue with the function call metaphor The `loop` call defines 3 things: - the starting point of the function - the argument name of the function - the **initial values** of those arguments When you need to call again that function with new arguments, you use `recur` with **new values**. When you don't need to recur, well... dont call `recur` :) and just evaluate a last expression which is the result of the `loop` expression. regards Laurent Le dimanche 26 décembre 2021 à 02:35:47 UTC+1, hank@gmail.com a écrit : > Thank for the answers. > Trying to recur with '(recur (.read bfr))' resulted in a: > Syntax error (UnsupportedOperationException) compiling recur at > (*cider-repl ~:localhost:41097(clj)*:237:9). > Can only recur from tail position > So I changed the code (see below). > > And now it complains that a previous form that was working '(.append > etc..') doesn't and the same error remains. > > user> (pt5 myfile) > > Execution error (IllegalArgumentException) at java.lang.Character/toChars > (Character.java:8572). > Not a valid Unicode code point: 0x > > (defn pt5 [file] > >(let [afr (FileReader. file); instances of FileReader, BufferedReader, > StringBuffer > bfr (BufferedReader. afr) > ct (StringBuilder.) > this-list (list afr bfr ct)] > ; (apply println this-list) > (loop [val (.read bfr)] >(when (not (= val -1)) > (.append ct (Character/toChars (.read bfr >(recur val)) > ; when finished... > (.toString ct))) > > Harder then it seemed at first sight... > -- Hank > > > -- You received this message because you are subscribed to the Google Groups "Clojure" group. To post to this group, send email to clojure@googlegroups.com Note that posts from new members are moderated - please be patient with your first post. To unsubscribe from this group, send email to clojure+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/clojure?hl=en --- You received this message because you are subscribed to the Google Groups "Clojure" group. To unsubscribe from this group and stop receiving emails from it, send an email to clojure+unsubscr...@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/clojure/66318891-e779-4a3c-818c-a235f7b32550n%40googlegroups.com.
Re: Pesky java interop bug with 0xFFFFFFF error in BuferredReader
Hi, In the quoted example the `recur` call is *inside* the `when` which is a huge difference because there is in this case an halting condition to get out of the loop ;) regards Laurent Le dimanche 26 décembre 2021 à 14:41:15 UTC+1, hank@gmail.com a écrit : > 2021-12-25, 21:11:46 UTC-3, LaurentJ wrote: > "Hi, > > Your loop/recur usage is wrong, your error may be because your loop has no > halting condition." > > Hi Laurent -- > I actually took inspiration from one of the sources you posted: > (import '(javax.sound.sampled AudioSystem AudioFormat$Encoding)) > > (let [mp3-file (java.io.File. "tryout.mp3") > audio-in (AudioSystem/getAudioInputStream mp3-file) > audio-decoded-in (AudioSystem/getAudioInputStream > AudioFormat$Encoding/PCM_SIGNED audio-in) > buffer (make-array Byte/TYPE 1024)] > (loop [] > (let [size (.read audio-decoded-in buffer)] > (when (> size 0) > ;do something with PCM data > (recur) > > > -- You received this message because you are subscribed to the Google Groups "Clojure" group. To post to this group, send email to clojure@googlegroups.com Note that posts from new members are moderated - please be patient with your first post. To unsubscribe from this group, send email to clojure+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/clojure?hl=en --- You received this message because you are subscribed to the Google Groups "Clojure" group. To unsubscribe from this group and stop receiving emails from it, send an email to clojure+unsubscr...@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/clojure/93ed9e36-bd43-4592-b5c3-89187304d75cn%40googlegroups.com.
Re: Pesky java interop bug with 0xFFFFFFF error in BuferredReader
2021-12-25, 21:11:46 UTC-3, LaurentJ wrote: "Hi, Your loop/recur usage is wrong, your error may be because your loop has no halting condition." Hi Laurent -- I actually took inspiration from one of the sources you posted: (import '(javax.sound.sampled AudioSystem AudioFormat$Encoding)) (let [mp3-file (java.io.File. "tryout.mp3") audio-in (AudioSystem/getAudioInputStream mp3-file) audio-decoded-in (AudioSystem/getAudioInputStream AudioFormat$Encoding/PCM_SIGNED audio-in) buffer (make-array Byte/TYPE 1024)] (loop [] (let [size (.read audio-decoded-in buffer)] (when (> size 0) ;do something with PCM data (recur) -- You received this message because you are subscribed to the Google Groups "Clojure" group. To post to this group, send email to clojure@googlegroups.com Note that posts from new members are moderated - please be patient with your first post. To unsubscribe from this group, send email to clojure+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/clojure?hl=en --- You received this message because you are subscribed to the Google Groups "Clojure" group. To unsubscribe from this group and stop receiving emails from it, send an email to clojure+unsubscr...@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/clojure/c293ceb0-d187-41f9-b0a4-68860cb55bd2n%40googlegroups.com.
Re: Pesky java interop bug with 0xFFFFFFF error in BuferredReader
Thanks, Harold. You see, that was an exercise in Java interop - I know about slurp, but I was trying to understand what was going on there. -- Hank -- You received this message because you are subscribed to the Google Groups "Clojure" group. To post to this group, send email to clojure@googlegroups.com Note that posts from new members are moderated - please be patient with your first post. To unsubscribe from this group, send email to clojure+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/clojure?hl=en --- You received this message because you are subscribed to the Google Groups "Clojure" group. To unsubscribe from this group and stop receiving emails from it, send an email to clojure+unsubscr...@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/clojure/dc222f28-0f21-4f02-b79c-1d0f4db4f95bn%40googlegroups.com.
