This syntax doesn't work:
>> do load/header {rebol [Title: "Hello World"] Print System/Header/Script/Title }
** Script Error: Invalid path value: Header
** Near: Print System/Header/Script/Title
I want to get the meta-data in header.
My goal is mostly to be able to execute a whole rebol source including header to the clipboard and execute it in console by doing something like do read clipboard:// that doesn't work if I include the header, I can't strip it since I need it.
Rewritten in response to comment.
Use load/header/next to create a two-item block: the script header followed by the script content:
loaded: load/header/next {rebol [Title: "Hello World"] Print "this is my script"^/a: 99 + 5 print a}
probe loaded/1 ;; shows the header
do loaded/2 ;; executes the script
Related
readLine() doesn't support line editing and recalling previous commands, eg:
while true:
var name: string = readLine(stdin)
echo "Hi, ", name, "!"
Has no editing. But if I compile that and wrap it in rlwrap:
$ rlwrap read_test
It works as I hope. with editable and recallable lines, provided by the readline library.
readLineFromStdin() almost works, but doesn't support ctrl+d, it returns an empty string on ctrl+d, which is indistinguishable from a newline.
How can I do this in pure Nim? Thanks!
Ctrl+D is an EOF "signal", and thus you can catch the EOF in your input:
while not endOfFile(stdin):
var name: string = readLine(stdin)
echo "Hi, ", name, "!"
The procedure readLineFromStdin (https://github.com/nim-lang/Nim/blob/version-1-2/lib/impure/rdstdin.nim#L54) is not that complex, and you can re-write your own adding the above code to it.
While #xbello's answer is correct, if you want to use a package, we ended up using https://github.com/jangko/nim-noise, which supports C-d handling and loads of other features.
I am trying to run following very simple code:
open Str
print (Str.first_chars "testing" 0)
However, it is giving following error:
$ ocaml testing2.ml
File "testing2.ml", line 2, characters 0-5:
Error: Syntax error
There are no further details in the error message.
Same error with print_endline also; or even if no print command is there. Hence, the error is in part: Str.first_chars "testing" 0
Documentation about above function from here is as follows:
val first_chars : string -> int -> string
first_chars s n returns the first n characters of s. This is the same
function as Str.string_before.
Adding ; or ;; at end of second statement does not make any difference.
What is the correct syntax for above code.
Edit:
With following code as suggested by #EvgeniiLepikhin:
open Str
let () =
print_endline (Str.first_chars "testing" 0)
Error is:
File "testing2.ml", line 1:
Error: Reference to undefined global `Str'
And with this code:
open Str;;
print_endline (Str.first_chars "testing" 0)
Error is:
File "testing2.ml", line 1:
Error: Reference to undefined global `Str'
With just print command (instead of print_endline) in above code, the error is:
File "testing2.ml", line 2, characters 0-5:
Error: Unbound value print
Note, my Ocaml version is:
$ ocaml -version
The OCaml toplevel, version 4.02.3
I think Str should be built-in, since opam is not finding it:
$ opam install Str
[ERROR] No package named Str found.
I also tried following code as suggested in comments by #glennsl:
#use "topfind"
#require "str"
print (Str.first_chars "testing" 0)
But this also give same simple syntax error.
An OCaml program is a list of definitions, which are evaluated in order. You can define values, modules, classes, exceptions, as well as types, module types, class types. But let's focus on values so far.
In OCaml, there are no statements, commands, or instructions. It is a functional programming language, where everything is an expression, and when an expression is evaluated it produces a value. The value could be bound to a variable so that it could be referenced later.
The print_endline function takes a value of type string, outputs it to the standard output channel and returns a value of type unit. Type unit has only one value called unit, which could be constructed using the () expression. For example, print_endline "hello, world" is an expression that produces this value. We can't just throw an expression in a file and hope that it will be compiled, as an expression is not a definition. The definition syntax is simple,
let <pattern> = <expr>
where is either a variable or a data constructor, which will match with the structure of the value that is produced by <expr> and possibly bind variable, that are occurring in the pattern, e.g., the following are definitions
let x = 7 * 8
let 4 = 2 * 2
let [x; y; z] = [1; 2; 3]
let (hello, world) = "hello", "world"
let () = print_endline "hello, world"
You may notice, that the result of the print_endline "hello, world" expression is not bound to any variable, but instead is matched with the unit value (), which could be seen (and indeed looks like) an empty tuple. You can write also
let x = print_endline "hello, world"
or even
let _ = print_endline "hello, world"
But it is always better to be explicit on the left-hand side of a definition in what you're expecting.
So, now the well-formed program of ours should look like this
open Str
let () =
print_endline (Str.first_chars "testing" 0)
We will use ocamlbuild to compile and run our program. The str module is not a part of the standard library so we have to tell ocamlbuild that we're going to use it. We need to create a new folder and put our program into a file named example.ml, then we can compile it using the following command
ocamlbuild -pkg str example.native --
The ocamlbuild tool will infer from the suffix native what is your goal (in this case it is to build a native code application). The -- means run the built application as soon as it is compiled. The above program will print nothing, of course, here is an example of a program that will print some greeting message, before printing the first zero characters of the testing string,
open Str
let () =
print_endline "The first 0 chars of 'testing' are:";
print_endline (Str.first_chars "testing" 0)
and here is how it works
$ ocamlbuild -package str example.native --
Finished, 4 targets (4 cached) in 00:00:00.
The first 0 chars of 'testing' are:
Also, instead of compiling your program and running the resulting application, you can interpret your the example.ml file directly, using the ocaml toplevel tool, which provides an interactive interpreter. You still need to load the str library into the toplevel, as it is not a part of the standard library which is pre-linked in it, here is the correct invocation
ocaml str.cma example.ml
You should add ;; after "open Str":
open Str;;
print (Str.first_chars "testing" 0)
Another option is to declare code block:
open Str
let () =
print (Str.first_chars "testing" 0)
Here's my test program:
use Readline;
shell 'clear';
my $r = Readline.new;
loop {
my $a = $r.readline("> ");
{say ''; last} if not defined $a;
$r.add-history( $a );
say $a;
}
After I enter any string, it exits with the following message:
> abc
Internal error: unhandled encoding
in method CALL-ME at /opt/rakudo-pkg/share/perl6/sources/24DD121B5B4774C04A7084827BFAD92199756E03 (NativeCall) line 587
in method readline at /home/evb/.perl6/sources/D8BAC826F02BBAA2CCDEFC8B60D90C2AF8713C3F (Readline) line 1391
in block <unit> at abc.p6 line 7
If I comment the line shell 'clear';, everything is OK.
This is a bit of a guess, but I think when you tell your shell to clear the screen, it's sending a control character or control sequence as input to the terminal emulator. Readline is reading from that same stream, and those characters end up at the beginning of your "line" when you try to read a line. Those characters aren't valid UTF-8 (the default encoding) and so can't be interpreted as a string. You'll know more if you open the text files in the stack trace and look at the relevant line numbers.
You can try calling reset-terminal or reset-line-state to see if you can get rid of that character. What I would do in a low level programming language is to do a nonblocking read of the input (without converting it into a string), but I can't find the API for that in the Perl 6 library.
Apparently un-catchable error while toying around with Rebol/Core (278-3-1) to make a kind-of web-server to serve a static text, containing a redirect link to a new service location.
The specific location of the error appear to be in example code written by Carl Sassenrath himself, back in 2006, so I'm kind of baffled there could be an undetected error after all these years.
I have three of these scripts running simultaneous, monitoring three individual ports. Essentially the script works as it should... when accessed repeatedly with multiple browsers at once (on all parallel scripts) it appear appear to be pretty stable... but one after another they fail. Sometimes after 2 minutes, sometimes after 20 minutes - after adding the print statements sometimes even after 60 minutes - but eventually they will fail like this:
** Script Error: Out of range or past end
** Where: forever
** Near: not empty? request: first http-port
I've tried wrapping just about every part of the program loop in a try[][exception], but the error still occurs. Unfortunately my search-fu appear to be weak this time of year, as I haven't found anything that could explain the problem.
The code is a cut down version of Carl Sassenrath's Tiny Web Server, slightly modified to bind to a specific IP, and to emit HTML instead of loading files:
REBOL [title: "TestMovedServer"]
AppName: "Test"
NewSite: "http://test.myserver.org"
listen-port: open/lines tcp://:81 browse http://10.100.44.6?
buffer: make string! 1024 ; will auto-expand if needed
forever [
http-port: first wait listen-port
clear buffer
while [not empty? request: first http-port][
print request
repend buffer [request newline]
print "----------"
]
repend buffer ["Address: " http-port/host newline]
print buffer
Location: ""
mime: "text/html"
parse buffer ["get" ["http" | "/ " | copy Location to " "]]
data: rejoin [{
<HTML><HEAD><TITLE>Site Relocated</TITLE></HEAD>
<BODY><CENTER><BR><BR><BR><BR><BR><BR>
<H1>} AppName { have moved to } NewSite {</H1>
<BR><BR><BR>Please update the link you came from.
<BR><BR><BR><BR><BR>(Continue directly to the requested page)
</CENTER></BODY></HTML>
}]
insert data rejoin ["HTTP/1.0 200 OK^/Content-type: " mime "^/^/"]
write-io http-port data length? data
close http-port
print "============"
]
I'm looking forward to see what you guys make out of this!
You get an error when trying to read from a closed connection. This seems to work.
n: 0
forever [
http-port: first wait listen-port
clear buffer
if attempt [all [request: first http-port not empty? request]] [
until [
print request
repend buffer [request newline]
print "----------"
any [not request: first http-port empty? request]
]
repend buffer ["Address: " http-port/host newline]
print buffer
Location: ""
mime: "text/html"
parse buffer ["get" ["http" | "/ " | copy Location to " "]]
data: rejoin [{
<HTML><HEAD><TITLE>Site Relocated</TITLE></HEAD>
<BODY><CENTER><BR><BR><BR><BR><BR><BR>
<H1>} AppName n: n + 1 { has moved to } NewSite {</H1>
<BR><BR><BR>Please update the link you came from.
<BR><BR><BR><BR><BR>(Continue directly to the requested page)
</CENTER></BODY></HTML>
}]
insert data rejoin ["HTTP/1.0 200 OK^/Content-type: " mime "^/^/"]
write-io http-port data length? data
]
attempt [close http-port]
print "============"
]
Let us see the documentation for empty?
Summary:
Returns TRUE if a series is at its tail.
Usage:
empty? series
Arguments:
series - The series argument. (must be: series port bitset)
So empty? requires series, port or bitset or string argument. Your variable (request) is getting any of them as long as there is connection to the port is open. empty? can thereafter determine whether it is at the tail of variable.
When the connection is closed/interrupted, your variable receives nothing but there is access error connecting to port. Error does not have tail. empty? gets confused and crashes with error.
sqlab has replaced empty? with attempt
if attempt [all [request: first http-port not empty? request]]
The ATTEMPT function is a shortcut for the frequent case of:
error? try [block]
with all he is guarding against error as well as none.
ATTEMPT returns the result of the block if an error did not occur. If an error did occur, a NONE is returned.
also with until and
any [not request: first http-port empty? request]
he is guarding against both.
Therefore his code is working.
I use a custom function (currently residing in .vimrc) and not :make or another direct command line tool to compile/check my currently edited file for errors. Like this:
function! CompileMyCode(...)
set errorformat=Error:\ %m\\,\ in\ line\ %l
let l:output = "Error: bad code!, in line 9"
return l:output
endfunction
command! -nargs=* CompileMyCode :call CompileMyCode(<f-args>)
when using the new command in command mode, no error window shows up.
:CompileMyCode | cwindow
What am I doing wrong?
Edit:
I now tried the following which also does not open any cwindow.
function! CompileMyCode(...)
set errorformat=Error:\ %m\\,\ in\ line\ %l
let l:output = "Error: bad code!, in line 9"
" I tried both of the following lines separately
cexpr l:output
call setqflist([l:output])
endfunction
The proposed commands cexpr and setqflist() do not open the cwindow correctly in my example. Maybe somebody can propose a complete solution?
Edit 2:
The main problem is solved. Here is my current code:
let l:result = expand("%").'|8| errortext'
cexpr [ l:result, l:result ]
caddexpr ''
cwindow
This example respects a default error format that vim seems to support. When cexpring the actual error output and using an errorformat the cwindow seems to ignore that.
Nevertheless, I wanted stick to a default error format anyway in the output, not having to rely on a custom errorformat
Thx for your answers!
I did something similar using cexpr l:output instead of returning the string and that placed the output of the compile in the quickfix window. You can see my vim function here: http://www.zenskg.net/wordpress/?p=199
Update
Adding a blank line to the quickfix list seems to allow the cwindow to appear. For example:
function! MyCompile()
let l:output = "Error: line 1"
cexpr l:output
caddexpr ""
cwindow
endfunction
If you already have access to the error information as structured data in Vim (or can easily obtain it), you can use setqflist().