How I can get "Maintenance" value from site
using a MQL4 script ?
As I understand, I must set an internet connection, get data from site, parse it and get data.
Is there a way how I can do it?
I'll be grateful for any example.
Fact #1: MQL4 syntax restricts calling external sub-process:
This means ( if not using a DLL-workaround ) the whole task would require to re-invent a wheel and build the HTML-parser inside MQL4. Doable but a waste of anyone's resources.
Fact #2: There are better ways to choose from:
Once going to use a DLL-imported functionalities, one may either just bypass the MQL4 code-execution restrictions and call Windows-API services to fork sub-process and make things move forwards, however Windows-API, in my opinion, is rather a feature rich interfacing framework, but for a pretty low-level access to elementary services, so you finally can find yourself re-inventing wheel again, well, now "outside" from the MQL4 sandbox restrictions.
If you do not restrict our imagination, your project may benefit from rapid-prototyping in Python and setup a peer-to-peer distributed messaging/control in a heterogeneous Python / MQL4 environment.
Besides other benefits, Python strengths in smart and powerful ( not only ) web-content processing is fabulous, so this distributed approach will open your MQL4 projects into strategically new, unseen dimensions.
Python smart-scraping ( not a dumb-force one ):
def askAtPublisherWebURL( aControlDICT,
aURL = "https://globalde?.?.?.?y?.com/en/products/.../...-DLON?Class_type=class_symbol=???&Class_exchange=???&ps=999&md=03-2014",
anOPT = "ESX",
aMaturityDATE = "03-2014",
anEmailRECIPIENT = "Me.Robot-GWY-2013-PoC#gmail.com",
aFileNAME = "ESX_2014-03_anObservedStateTIMESTAMP[]"
):
import time, urllib, re, winsound, urllib2 # late, dirty import
try:
aReturnFLAG = True
anOutputSTRING = "|TRYING: " + aURL # a crash-proof proxy-value for a case IOError <EXC> would appear
# --------------------------------------------------------# urllib2 MODE
anInputHANDLER = urllib2.urlopen( aURL, None, 120 ) # urllib2 MODE with a 120 [sec] timeout before urllib2.URLError ... still gets stuck during peak-hours ( on aMaturityDATE )
aListOfLINEs = anInputHANDLER.readlines()
anInputHANDLER.close()
# --------------------------------------------------------# urllib2 MODE
except urllib2.URLError as anExcREASON:
aReturnFLAG = False
# no RET here // JMP .FINALLY: to log IOError....
except exceptions.IOError as ( ErrNO, ErrSTR ): # an IOError <EXC> hase appeared, handle with care before JMP .FINALLY:
aReturnFLAG = False
else: # no IOError or any other <EXC>, process the <content> .. JMP .FINALLY:
# ------------------------------------------------------# HTML-processor
# smart html-processing goes here
# ...
# ------------------------------------------------------# HTML-processor
finally: # in any case do all this TIDY-UP-BEFORE-EXIT
# fileIO + pre-exit ops
# sendMsg4MQL() --> SIG MT4
return aReturnFLAG # MISRA-motivated single point of RET
For hawkish Pythoneers, the post intentionally uses non-PEP-8 source code formatting as it is authors experience that during a learning phase, code read-ability improves the focus on task solution and helps getting used to the underlying concepts rather than to spend efforts on formally adhering typography. Hope the principle of providing help is respected and the non-PEP-8 styling format is forgiven in the name of the ease of reading.
Related
Assuming that I set one environment variable before launching a logic simulation of my circuit wrapped in a testbench written in SystemVerilog, I want to check whether it is possible to read the variable and try to map it to a net of the circuit.
For instance:
#### from the bash script that invokes the logic simulator ####
export NET_A=tb_top.module_a.submodule_b.n1
//// inside the tb_top in system verilog ////
import "DPI-C" function string getenv(input string env_name);
always_ff #(posedge clk, nenedge rst_n) begin
if (getenv("NET_A") == 1'b1) begin
$display("Hello! %s has the value 1", getenv("NET_A"));
end
end
In the example above I simply want to check whether the current net i.e., NET_Ais assigned at a certain point in the simulation the logic value of 1.
Thanks in advance
SystemVerilog has a C-based API (Verilog Procedural Interface VPI) that gives you access to a simulator's database. There are routines like vpi_get_handle_by_name which gives you a handle to an signal looked up by a string name. And then you can use vpi_get_value the gives you the current value of that signal.
Use of the VPI needs quite a bit of additional knowledge and many simulators give you built-in routines to handle this common application without having to break into C code. In Modelsim/Questa, it is called Signal_Spy.
But regardless of whether you use the VPI or tool specific routines, looking up a signal by string name has severe performance implications because it prevents many optimizations. Unless a signal represents a storage element, it usually does not keep its value around for queries.
It would be much better to use the signal path name directly
vlog ... +define+NET_A=tb_top.module_a.submodule_b.n1
Then in your code
if (`NET_A == 1'b1) begin
I am looking at some old MetaEditor4 / MQL4 code, where a local variable was declared twice:
......
1 int start()
2 {
3 if (1==2)
4 {
5 double myVar = 1;
6 } else
7 {
8 double myVar = 2;
9 }
10 return;
11 }
.......
The compilation process in MetaEditor, version 5.00, build 1601, fails with:
'myVar' - variable already defined in line 8.
If I remove the line 8, the compilation goes well.
My questions are:
1. Is there any option in MetaEditor that tolerates the multiple declaration of a local variable?
2. In previous versions of MetaTrader Terminal 4 / MetaEditor and .MQ4 code: was it possible to declare a local variable more than once in such a situation?
3. The MetaEditor has the version 5.00, build 1601, but the extension of the code is .mq4 and it was installed together with the MetaTrader Terminal software MetaTrader4 ( from FXCM ). Therefore I assume I can still use .MQ4 code with it. Is there any chance to get a pure MQL4 installation from somewhere?
Whenever I install mt4 ( from e.g.: mt4 download), it ends up
with the mt5 installer.
Prologue:
The worlds of MQL4 evolve. One may try to circumvent this fact, but finally, at one's own disappointment, attempts to avoid evolution will sooner or later go in vain.
Having been thrown into a need to re-engineer code-base spanning a few man*decades in size, I can tell you many stories about what worked and what did not.
An "Old code" v/s a New-MQL4.56789
If just one thing ought be taken from this, never try to "circumvent" New-MQL4, but rather review the code and refactor the "Old code" - this is a way safer way to survive ( way longer ).
Yes, there are chances ( zero warrants, just a few chances left temporarily on the table ) the new compiler version will remain able to generate an executable version of the code, but given a new set of rules have already come in the city, the game will not last long.
Ad 1 + 2 )Compiler still tolerates multiple declarations, but not in one scope
If new version of a compiler defined that any variable is declared only relative to it's scope of validity, the serious programmer ought take this as a general principle. The code above actually has other problem, right nailed to the scope-of-validity:
2 ...
3 if ( 1 == 2 ) {
4 ...
5 double myVar = 1; // myVar declared & known |since HERE >
6 ... // masking any other,|known HERE :
7 ... // |known HERE :
8 } else // |till HERE . Undef further
9 {
10 ...
11 double myVar = 2; // myVar declared & known |since HERE >
12 // masking any other,|known HERE :
13 ... // |known HERE :
14 } // |till HERE . Undef further
so, if there were any _global_ scope'd variable with the same name myVar, it will not be "visible" during an existence of locally declared variable, wearing the same name.
Finally, having the code-execution escaped from any of the lines 8 or 14 further, the locally there declared variable double myVar simply ceased to exist anymore and this behaviour is principally correct ( and the "older" compiler releases were tolerating a sort of dangerous habit of side-effects, during years of tolerating scope-of-validity spillover(s), so it was the high time to clean the rules, so as to meet a fair level of C/S standards.
Ad 3) language receives a lot from MQL5, even if not used in MQL4
Yes, MetaEditor will correctly compile a MQL4 code into .mq4 code-execution format, no problem here. Even an auto-update process started to go independently from MT4 Terminal platform (auto-)updates ( so you will quite often see new Help file coming and enforced re-compilation of all your localhost visible .MQ4 assets into updated .EX4 format, so "Do not panic."
Better never install a Broker-agnostic MT4, always go to your Broker's Support and get installation package & help from your Broker. This is business relation you have signed in a contract, so keep these strings as you are going to trade your money on a table they operate under the set Terms & Conditions. Some Brokers have means of platform customisations, so rather benefit from their custom settings that will match their Server-side automation.
It is more a question of economy of R&D efforts. ( May read a lot about language components injected from the MQL5 domain in the IDE Editor MQL4 Help ). This is a natural will of the product design strategy, not to double efforts on a dual-line. Without doubts, there are many details the Help file could be improved and better maintained, the common sense here is to live with the facts and re-learn what newly introduced features remain neutral for the MQL4 code base and what new things may actually help one a lot in aspects, where older compilers were short in powers.
If one objects that some compiler / platform re-design steps were bad, I would agree on a single-thread, platform-critical, potentially blocking, concentration of executing all the CustomIndicator-s in just one SPoF-thread.
But C'est La Vie, until system architects will not review this SPoF, the platform will remain susceptible to crashes from this feature, but the ball is on the other side of the court and a change will have to be implemented there.
the code might be run with 'strict' or non-strict mode.
strict means that variable must be declared within its scope, non-strict - all the mess that you have now.
so put #property strict at the beginning of the file
open a demo account somewhere and install mt4 there. demo can be valid for 30 days only with registration via web-site of a broker or with unlimited and demo opened from mt4 (example - Alpari)
I am using Chumak in erlang, opening a ROUTER socket.
I have a handful (4 or so) clients that use the Python zmq library to send REQ requests to this server.
Things work fine most of the time, but sometimes a client will have disconnect issues (reconnecting automatically is in the client code, and it works). I've found that when an error occurs in one client connection, it seems to move on to others as well, and I get a lot of
** {{noproc,{gen_server,call,[<0.31596.16>,incomming_queue_out]}},
on the server.
On the server side, I'm just opening one chumak socket and looping:
{ok, Sock} = chumak:socket( router ),
{ok, _} = chumak:bind( Sock, tcp, "0.0.0.0", ?PORT ),
spawn_link( fun() -> loop( Sock ) end ),
...
loop( CmdSock ) ->
{ok, [Identity, <<>>, Data]} = chumak:recv_multipart( Sock ),
...
The ZeroMQ docs seem to imply that one listening socket is enough unless I have many clients.
Do I misunderstand them?
No, there is no need to increase number of Socket instances
Abstractions are great to reduce a need to understand all the details under the hood for a typical user. That ease of life stops whenever such user has to go into performance tuning or debugging incidents.
Let's step in this way:
- unless some mastodon beast sized data payloads are to get moved through, there is quite enough to have a single ROUTER-AccessPoint into a Socket-instance, for say tens, hundreds, thousands of REQ-AccessPoints on the client side(s).
- yet, such numbers will increase the performance envelope requirements for the ROUTER-side Context-instance, so as to remain capable of handling all the Scalable Formal Communication Archetype ( pre-scribed ) handling, so as to all happen in due time and fair fashion.
This means, one can soon realise benefits from spawning Context-instances with more than its initial default solo-thread + in all my high-performance setups I advocate for using zmq.AFFINITY mappings, so as to squeeze indeed a max performance on highest-priority Socket-instances, whereas leaving non-critical resources sharing a common sub-set of the Context-instance's IO-thread-pool.
Next comes RAM
Yes, the toys occupy memory.
Check all the .{RCV|SND}BUF, .MAXMSGSIZE, .{SND|RCV}HWM, .BACKLOG, .CONFLATE
Next comes LINK-MANAGEMENT
Do not hesitate to optimise .IMMEDIATE, .{RCV|SND}BUF, .RECONNECT_IVL, .RECONNECT_IVL_MAX, .TCP_KEEPALIVE, .TCP_KEEPALIVE_CNT, .TCP_KEEPALIVE_INTVL, .TCP_KEEPALIVE_IDLE
Always set .LINGER right upon instantiations, as drop-outs cease to be lethal.
Next may come a few defensive and performance helper tools:
.PROBE_ROUTER, .TCP_ACCEPT_FILTER, .TOS, .HANDSHAKE_IVL
Next step?
If no memory-related troubles remain in the game and once mentioning reconnections, my suspect would be to rather go and setup .IMMEDIATE + possibly let ROUTER benefit from explicit PROBE_ROUTER signalling.
I was wondering if you know of any way to use prolog for stream processing, that is, some kind of reactive programming, or at least to let a query run on a knowledge base that is continuously updated (effectively a stream), and continuously output the output of the reasoning?
Anything implemented in the popular "prologs", such as SWI-prolog?
You can use Logtalk's support for event-driven programming to define monitors that watch for knowledge base update events and react accordingly. You can run Logtalk using most Prolog systems as the backed compiler, including SWI-Prolog.
The event-driven features are described e.g. in the user manual:
http://logtalk.org/manuals/userman/events.html
The current distribution contains some examples of using events and monitors. An interesting one considering your question is the bricks example:
https://github.com/LogtalkDotOrg/logtalk3/tree/master/examples/bricks
Running this example first and then looking at its code should give you as good idea of what you can do with system wide events and monitors.
XSB has stream processing capabilities. See page 14 in the
XSB Manual
I'm working on something related, in project pqConsole already there is the basic capability: report to the user structured data, containing actionable areas (links) that call back in Prolog current state, hence the possibility to expose actions and react appropriately (hopefully).
It's strictly related to pqConsole::win_write_html, showcasing recent Qt capabilities of SWI-Prolog.
Here an example of a snippet producing only a simple formatted report, I'll try now to add the reactive part, so you can evaluate if you find expressive this basic system. Hints are welcome...
/* File: win_html_write_test.pl
Author: Carlo,,,
Created: Aug 27 2013
Purpose: example usage win_html_write/1
*/
:- module(win_html_write_test,
[dir2list/1
]).
:- [library(http/html_write)].
:- [library(dirtree)].
dir2list(Path) :-
dirtree(Path, DirTree),
% sortree(compare_by_attr(name), DirTree, Sorted), !,
DirTree = Sorted,
phrase(html([\css,
\logo,
hr([]),
ul(\dirtree2html(Sorted, [])),
br([])]), Tokens),
with_output_to(atom(X), print_html(Tokens)),
win_html_write(X),
dump_page_to_debug(X).
css --> html(style(type='text/css',
['.size{color:blue;}'
])).
logo --> html(img([src=':/swipl.png'],[])).
dirtree2html(element(dir, A, S), Parents) -->
html(li([\elem2html(A),
ul(\elements2html(S, [A|Parents]))])).
dirtree2html(element(file, A, []), _Parents) -->
html(li(\elem2html(A))).
elem2html(A) -->
{memberchk(name=N, A),
memberchk(size=S, A)
},
html([span([class=name], N), ' : ', span([class=size], S)]).
elements2html([E|Es], Parents) -->
dirtree2html(E, Parents),
elements2html(Es, Parents).
elements2html([], _Parents) --> [].
dump_page_to_debug(X) :-
open('page_to_debug.html', write, S),
format(S, '<html>~n~s~n</html>~n', [X]),
close(S).
This snippet depends on dirtree, that should be installed with
?- pack_install(dirtree).
edit With 3 modifications now the report has the ability to invoke editing of files:
call to get paths in structure
dir2list(Path) :-
dirtree(Path, DirTreeT),
assign_path(DirTreeT, DirTree),
...
request a specialized output for files only
dirtree2html(element(file, A, []), _Parents) -->
html(li(\file2html(A))).
finally, the 'handler' - here just place a request to invoke the editor
file2html(A) -->
{memberchk(name=N, A),
memberchk(path=P, A),
memberchk(size=S, A)
},
html([span([class=name],
[a([href='writeln(editing(\'~s\')), edit(\'~s\')'-[N,P]], N)]
), ' : ', span([class=size], S)]).
and now the file names are clickable, write a message and get edited if requested: a picture
You should check out RTEC: Run-Time Event Calculus:
https://github.com/aartikis/RTEC
RTEC is an open-source Event Calculus dialect optimised for stream reasoning. It is written in Prolog and has been tested under YAP 6.2.
Feature highlights:
Interval-based.
Sliding window reasoning.
Interval manipulation constructs for non-inertial fluents.
Caching for hierarchical knowledge bases.
Support for out-of-order data streams.
Indexing for handling efficiently irrelevant data.
There is also a mention of it on the SWI-Prolog website:
https://www.swi-prolog.org/pack/file_details/prologmud_I7/prolog/ec_planner/RTEC/README.md
which presumably relies on:
https://www.swi-prolog.org/pldoc/doc/_SWI_/library/dialect/yap.pl
I don't know why this hasn't been brought up so far, but in SWI-Prolog there is prolog_listen, which can, amongst other things, monitor dynamic updates to the database:
I am using a Basys2 board to program a simple string detector to read patterns like "0101". I am using the Xilinix Design Suite 13.2 for this project. The .ucf file gives the following message.
ERROR:Place:1018 - A clock IOB / clock component pair have been found that are not
placed at an optimal clock IOB clock site pair.
The clock component <reset_IBUF_BUFG> is placed at site <BUFGMUX_X1Y1>.
The IO component <reset> is placed at site <IPAD73>.
Here's what my user constrains file looks like:
NET "x" LOC = "P11";# input switch
NET "reset" LOC = "K3"; # reset switch
NET "ck" LOC = "B8"; # clock
NET "b1" LOC = "A7"; # button 1
NET "b2" LOC = "M4"; # button 2
NET "z" LOC = "M5"; # output
One of the solutions I found online was to use this in the ucf:
CLOCK_DEDICATED_ROUTE = FALSE;
But unfortunately this didn't work for me. I'd appreciate any help with this problem.
The message appears to imply that your reset is being detected as a clock signal. That should be worrying - do you have processes which are sensitive to the edge of the reset signal?
You should (until you really know what you're doing) only use a couple of forms of process.
Asynchronous reset
process (clk, reset)
begin
if reset = '1' then
-- async reset stuff
elsif rising_edge(clk) then
-- sync stuff
end if;
end process;
Synchronous reset
process (clk)
begin
if reset = '1' then
--sync reset stuff
else
-- other sync stuff
end if;
end process;
Also, be careful - you still need to release the reset signal to these processes synchronously.
Here's a good read on various reset strategies:
http://www.xilinx.com/support/documentation/white_papers/wp272.pdf
Finally, using CLOCK_DEDICATED_ROUTE = FALSE; is another no-no for almost every situation.
In my case, I got that inscrutable error message because I mistyped:
always #(clk) begin
if (rst) begin
...
instead of
always #(posedge clk) begin
if (rst) begin
...
Apparently since it wasn't using the edge of clk, rst was now being treated like a clock and messing up routing.
I know this is an old question but I just hit this problem using ISE and Spartan 6; hopefully this answer will help someone (most likely me 6 months from now).