Related
There are Bollinger Bands with three RSI running in the basement.
I want to do a check on the signal in such a way that when 3 RSI struck the zone of the upper Bbands, there was a signal down and vice versa:
int start(){
double ma, stdev;
int i, limit, count=IndicatorCounted();
if(count<0) return(0);
limit=Bars-count;
if(limit>1) limit=Bars-1;
for(i=limit; i>=0; i--) {
RSI[i] =iRSI(Symbol(),Period(),rsi_period, PRICE_CLOSE,i);
RSI2[i]=iRSI(Symbol(),Period(),rsi_period_2,PRICE_CLOSE,i);
RSI3[i]=iRSI(Symbol(),Period(),rsi_period_3,PRICE_CLOSE,i);
}
for(i=limit; i>=0; i--) {
ma=iMAOnArray(RSI3,0,bb_period,0,0,i); // midle line
stdev=iStdDevOnArray(RSI3,0,bb_period,0,0,i); // dev
BBUP[i]=ma+bb_dev*stdev; // up line
BBDOWN[i]=ma-bb_dev*stdev; // down line
UP[i]=0;
DOWN[i]=0;
}
if(limit<Bars-1) limit++;
for(i=limit; i>0; i--) {
if(RSI[i] <= BBDOWN[i] && RSI[i+1] > BBDOWN[i+1] && RSI2[i] <= BBDOWN[i] && RSI2[i+1] > BBDOWN[i+1] && RSI3[i] <= BBDOWN[i] && RSI3[i+1] > BBDOWN[i+1]){
DOWN[i] = iLow(_Symbol, _Period, i);
}
if(RSI[i] >= BBUP[i] && RSI[i+1] < BBUP[i+1] &&W RSI2[i] >= BBUP[i] && RSI2[i+1] < BBUP[i+1] && RSI3[i] >= BBUP[i] && RSI3[i+1] < BBUP[i+1]){
UP[i]= iHigh(_Symbol, _Period, i);
}
}
The whole problem is that I have very crooked signals.
Appear where they should not be, and there is no where to be.
THE BEST PRACTICE:
Step 0: Let's first agree in written WHAT is the actual TARGET:
If the TARGET is to compute & paint on GUI the Bollinger Bands on RSI3[] values, the best way to do this is to use:
UPPER[i] = iBandsOnArray( RSI3, // ArrayAsSeries[]
array_calculation_depth, // reduce overheads
BB_MA_period, // BBands period
BB_StDev_MUL, // how many sigmas
BB_Zero_Shift, // #DEFINE BB_Zero_Shift 0
MODE_UPPER, // BBands upper line
i // shifting operator[i]
);
This way one may efficiently produce each of the { MODE_UPPER | MODE_MAIN | MODE_LOWER } Bollinger Bands lines here, consistently generated over dimension-less RSI3[] data, thus protecting the sense of any additive operations in signal-composition(s) with other, dimension-less data, as in { RSI2[], RSI[] }.
Step 1: visually check the lines to validate any signal-conditions:
Given the GUI shows lines accordingly, one may try to compose signal-conditions. The "hot"-bar [0] is a live-bar, where novice may encounter tricking signalling situations, if not handled with due professional care.
Step 2: implement signal-conditions in code:
Only after Step 0) & 1) took place and both meet one's own prior expectations, any code starts to make sense to get built.
From MQL4 docs https://docs.mql4.com/indicators/imaonarray
Unlike iMA(...), the iMAOnArray() function does not take data by
symbol name, timeframe, the applied price. The price data must be
previously prepared. The indicator is calculated from left to right.
To access to the array elements as to a series array (i.e., from right
to left), one has to use the ArraySetAsSeries() function.
RSI3 is currently orientated right to left (0 is most recent time point, limit is furthest element).
Same issue with iStdDevOnArray()
Fix those issues and it should work as you want. Whether there is any value in drawing Bollinger bands on RSI is another matter
Update
The function ArraySetAsSeries() can be used to swap the array between left-to-right and right-to-left
When you first initialise the RSI arrays ( in the OnInit() ) tell MetaTrader Terminal that they are timeseries.
ArraySetAsSeries(RSI1,True);
ArraySetAsSeries(RSI2,True);
ArraySetAsSeries(RSI3,True);
Then in main body, add ArraySetAsSeries(RSI3,False); before your second for loop to swap the array orientation. Then ArraySetAsSeries(RSI3,True); after the loop to restore the array orientation.
for(i=limit; i>=0; i--) {
RSI[i ] = iRSI(Symbol(),Period(),rsi_period,PRICE_CLOSE,i);
RSI2[i] = iRSI(Symbol(),Period(),rsi_period_2,PRICE_CLOSE,i);
RSI3[i] = iRSI(Symbol(),Period(),rsi_period_3,PRICE_CLOSE,i);
}
ArraySetAsSeries(RSI3,False);
for(i=limit; i>=0; i--) {
ma=iMAOnArray(RSI3,0,bb_period,0,0,i); // midle line
stdev=iStdDevOnArray(RSI3,0,bb_period,0,0,i); // dev
BBUP[i]=ma+bb_dev*stdev; // up line
BBDOWN[i]=ma-bb_dev*stdev; // down line
UP[i]=0;
DOWN[i]=0;
}
ArraySetAsSeries(RSI3,True);
if(limit<Bars-1) limit++;
for(i=limit; i>0; i--) {
if( RSI[i] <= BBDOWN[i] &&
RSI[i+1] > BBDOWN[i] &&
RSI2[i] <= BBDOWN[i] &&
RSI2[i+1] > BBDOWN[i] &&
RSI3[i] <= BBDOWN[i] &&
RSI3[i+1] > BBDOWN[i]) {
DOWN[i] = iLow(_Symbol, _Period, i);
}
if( RSI[i] >= BBUP[i] &&
RSI[i+1] < BBUP[i+1] &&
RSI2[i] >= BBUP[i] &&
RSI2[i+1] < BBUP[i+1] &&
RSI3[i] >= BBUP[i] &&
RSI3[i+1] < BBUP[i+1]) {
UP[i]= iHigh(_Symbol, _Period, i);
}
}
Basic indicator structure
You need to go through the MQL4 Documentation and learn the proper structure of an indicator. There needs to be an OnInit() function where you initialise values. Then an OnCalculate() function where you fill the indicator buffers.
//+-----------------------------------------------------------------+
//| Custom indicator initialization function |
//+-----------------------------------------------------------------+
int OnInit()
{
//--- indicator buffers mapping
ArraySetAsSeries(RSI3,True);
//---
return(INIT_SUCCEEDED);
}
//+-----------------------------------------------------------------+
//| Custom indicator iteration function |
//+-----------------------------------------------------------------+
int OnCalculate(const int rates_total,
const int prev_calculated,
const datetime& time[],
const double& open[],
const double& high[],
const double& low[],
const double& close[],
const long& tick_volume[],
const long& volume[],
const int& spread[])
{
// Do your calculations here
//--- return value of prev_calculated for next call
return(rates_total);
}
If you use iBandsOnArray() to calculate Bollinger bands you won't need to swap the array direction after it is set in OnInit()
If the indicator is compiling but crashing, you will need to debug it. Simplest way is to look at the errors in the log and add PrintFormat() statements throughout your code so you can see what the indicator is doing at different points and see where it crashes.
I've got a tree structure.
The task is to find the biggest sum/weight of path nodes, but i can only move n times. Thats ok, but going "up"/"back" cost nothing.
How can i accomplish that?
Below is my code, but the problem is that the each node can only be accessed once, so it doesnt work.
int mSum(Node* node, int mvLeft) {
if (node == nullptr) { return 0; }
if (mvLeft == 0) { return node->value; }
mvLeft--;
int sum = max(mSum(node->left, mvLeft), mSum(node->right, mvLeft));
return node->value + max(sum, mSum(node->parent, mvLeft + 1));
}
Here is the example graph. The numbers on the nodes represent the cost of getting to it. Each node can be visited only once except going "back".
The n step limit here is 3, we're counting entering the graph too, so the proper result is 21 because: 2->8->11.
If we would have limit of 4 steps the result would be 31: 2->10->8->11
My friend tried to do it with DFS, is he right? What's the best algorithm?
Good answer is taking multiple routes at the same time.
I mean we could go with 2-length limit:
2 left 0 right
1 left 1 right
0 left 2 right
Working, but somewhat slow, code :)
Its working time is 28s while other solutions can go with 2s (10 not known tests)
int mSum(Node* node, int mvLeft) {
mvLeft--;
if (mvLeft < 0) {
return 0;
}
else if (mvLeft == 0) {
return node->value;
}
if (node->left != nullptr && node->right != nullptr) {
int max = 0;
for (int i = 0; i <= mvLeft; i++) {
max = Max(max, mSum(node->left, i) + mSum(node->right, mvLeft - i));
}
return max + node->value;
}
else if (node->left != nullptr) {
return mSum(node->left, mvLeft) + node->value;
}
else if (node->right != nullptr) {
return mSum(node->right, mvLeft) + node->value;
}
return node->value;
}
Good morning. Sorry for the indelicate question, but how to create an expression that is not greater than 2 and less than 1 in Objective C
My code dosn't work
if([(UIPinchGestureRecognizer*)sender scale]<=2.0 || [(UIPinchGestureRecognizer*)sender scale]>=1.0)
|| is the operator for logical OR, which isn't what you want. You need &&, the operator for logical AND.So now your code will look like this:
if([(UIPinchGestureRecognizer*)sender scale]<=2.0 && [(UIPinchGestureRecognizer*)sender scale]>=1.0)
Let's break that down...
an expression that is not greater than 2
if (! (someValue > 2)) {
// someValue is not greater than 2
}
However, "not greater than 2" is the same thing as "less-than-or-equal to 2" so...
if (someValue <= 2) {
// someValue is not greater than 2
}
Now, for the second part...
an expression that is less than 1
if (someValue < 1) {
// someValue is less than 1
}
And...
an expression that is not greater than 2 and less than 1.
if ((someValue <= 2) && (someValue < 1)) {
// someValue is not greater than 2 and less than 1
}
However, if you think about it, any number that is less than 1 will also be "not greater than 2" so you don't even need that part.
if (someValue < 1) {
// someValue is less than 1... and it is also not greater than 2
}
I've been trying to implement a BASIC language interpreter (in C/C++) but I haven't found any book or (thorough) article which explains the process of parsing the language constructs. Some commands are rather complex and hard to parse, especially conditionals and loops, such as IF-THEN-ELSE and FOR-STEP-NEXT, because they can mix variables with constants and entire expressions and code and everything else, for example:
10 IF X = Y + Z THEN GOTO 20 ELSE GOSUB P
20 FOR A = 10 TO B STEP -C : PRINT C$ : PRINT WHATEVER
30 NEXT A
It seems like a nightmare to be able to parse something like that and make it work. And to make things worse, programs written in BASIC can easily be a tangled mess. That's why I need some advice, read some book or whatever to make my mind clear about this subject. What can you suggest?
You've picked a great project - writing interpreters can be lots of fun!
But first, what do we even mean by an interpreter? There are different types of interpreters.
There is the pure interpreter, where you simply interpret each language element as you find it. These are the easiest to write, and the slowest.
A step up, would be to convert each language element into some sort of internal form, and then interpret that. Still pretty easy to write.
The next step, would be to actually parse the language, and generate a syntax tree, and then interpret that. This is somewhat harder to write, but once you've done it a few times, it becomes pretty easy.
Once you have a syntax tree, you can fairly easily generate code for a custom stack virtual machine. A much harder project is to generate code for an existing virtual machine, such as the JVM or CLR.
In programming, like most engineering endeavors, careful planning greatly helps, especially with complicated projects.
So the first step is to decide which type of interpreter you wish to write. If you have not read any of a number of compiler books (e.g., I always recommend Niklaus Wirth's "Compiler Construction" as one of the best introductions to the subject, and is now freely available on the web in PDF form), I would recommend that you go with the pure interpreter.
But you still need to do some additional planning. You need to rigorously define what it is you are going to be interpreting. EBNF is great for this. For a gentile introduction EBNF, read the first three parts of a Simple Compiler at http://www.semware.com/html/compiler.html It is written at the high school level, and should be easy to digest. Yes, I tried it on my kids first :-)
Once you have defined what it is you want to be interpreting, you are ready to write your interpreter.
Abstractly, you're simple interpreter will be divided into a scanner (technically, a lexical analyzer), a parser, and an evaluator. In the simple pure interpolator case, the parser and evaluator will be combined.
Scanners are easy to write, and easy to test, so we won't spend any time on them. See the aforementioned link for info on crafting a simple scanner.
Lets (for example) define your goto statement:
gotostmt -> 'goto' integer
integer -> [0-9]+
This tells us that when we see the token 'goto' (as delivered by the scanner), the only thing that can follow is an integer. And an integer is simply a string a digits.
In pseudo code, we might handle this as so:
(token - is the current token, which is the current element just returned via the scanner)
loop
if token == "goto"
goto_stmt()
elseif token == "gosub"
gosub_stmt()
elseif token == .....
endloop
proc goto_stmt()
expect("goto") -- redundant, but used to skip over goto
if is_numeric(token)
--now, somehow set the instruction pointer at the requested line
else
error("expecting a line number, found '%s'\n", token)
end
end
proc expect(s)
if s == token
getsym()
return true
end
error("Expecting '%s', found: '%s'\n", curr_token, s)
end
See how simple it is? Really, the only hard thing to figure out in a simple interpreter is the handling of expressions. A good recipe for handling those is at: http://www.engr.mun.ca/~theo/Misc/exp_parsing.htm Combined with the aforementioned references, you should have enough to handle the sort of expressions you would encounter in BASIC.
Ok, time for a concrete example. This is from a larger 'pure interpreter', that handles a enhanced version of Tiny BASIC (but big enough to run Tiny Star Trek :-) )
/*------------------------------------------------------------------------
Simple example, pure interpreter, only supports 'goto'
------------------------------------------------------------------------*/
#include <stdio.h>
#include <stdlib.h>
#include <stdarg.h>
#include <string.h>
#include <setjmp.h>
#include <ctype.h>
enum {False=0, True=1, Max_Lines=300, Max_Len=130};
char *text[Max_Lines+1]; /* array of program lines */
int textp; /* used by scanner - ptr in current line */
char tok[Max_Len+1]; /* the current token */
int cur_line; /* the current line number */
int ch; /* current character */
int num; /* populated if token is an integer */
jmp_buf restart;
int error(const char *fmt, ...) {
va_list ap;
char buf[200];
va_start(ap, fmt);
vsprintf(buf, fmt, ap);
va_end(ap);
printf("%s\n", buf);
longjmp(restart, 1);
return 0;
}
int is_eol(void) {
return ch == '\0' || ch == '\n';
}
void get_ch(void) {
ch = text[cur_line][textp];
if (!is_eol())
textp++;
}
void getsym(void) {
char *cp = tok;
while (ch <= ' ') {
if (is_eol()) {
*cp = '\0';
return;
}
get_ch();
}
if (isalpha(ch)) {
for (; !is_eol() && isalpha(ch); get_ch()) {
*cp++ = (char)ch;
}
*cp = '\0';
} else if (isdigit(ch)) {
for (; !is_eol() && isdigit(ch); get_ch()) {
*cp++ = (char)ch;
}
*cp = '\0';
num = atoi(tok);
} else
error("What? '%c'", ch);
}
void init_getsym(const int n) {
cur_line = n;
textp = 0;
ch = ' ';
getsym();
}
void skip_to_eol(void) {
tok[0] = '\0';
while (!is_eol())
get_ch();
}
int accept(const char s[]) {
if (strcmp(tok, s) == 0) {
getsym();
return True;
}
return False;
}
int expect(const char s[]) {
return accept(s) ? True : error("Expecting '%s', found: %s", s, tok);
}
int valid_line_num(void) {
if (num > 0 && num <= Max_Lines)
return True;
return error("Line number must be between 1 and %d", Max_Lines);
}
void goto_line(void) {
if (valid_line_num())
init_getsym(num);
}
void goto_stmt(void) {
if (isdigit(tok[0]))
goto_line();
else
error("Expecting line number, found: '%s'", tok);
}
void do_cmd(void) {
for (;;) {
while (tok[0] == '\0') {
if (cur_line == 0 || cur_line >= Max_Lines)
return;
init_getsym(cur_line + 1);
}
if (accept("bye")) {
printf("That's all folks!\n");
exit(0);
} else if (accept("run")) {
init_getsym(1);
} else if (accept("goto")) {
goto_stmt();
} else {
error("Unknown token '%s' at line %d", tok, cur_line); return;
}
}
}
int main() {
int i;
for (i = 0; i <= Max_Lines; i++) {
text[i] = calloc(sizeof(char), (Max_Len + 1));
}
setjmp(restart);
for (;;) {
printf("> ");
while (fgets(text[0], Max_Len, stdin) == NULL)
;
if (text[0][0] != '\0') {
init_getsym(0);
if (isdigit(tok[0])) {
if (valid_line_num())
strcpy(text[num], &text[0][textp]);
} else
do_cmd();
}
}
}
Hopefully, that will be enough to get you started. Have fun!
I will certainly get beaten by telling this ...but...:
First, I am actually working on a standalone library ( as a hobby ) that is made of:
a tokenizer, building linear (flat list) of tokens from the source text and following the same sequence as the text ( lexems created from the text flow ).
A parser by hands (syntax analyse; pseudo-compiler )
There is no "pseudo-code" nor "virtual CPU/machine".
Instructions(such as 'return', 'if' 'for' 'while'... then arithemtic expressions ) are represented by a base c++-struct/class and is the object itself. The base object, I name it atom, have a virtual method called "eval", among other common members, that is the "execution/branch" also by itself. So no matter I have an 'if' statement with its possible branchings ( single statement or bloc of statements/instructions ) as true or false condition, it will be called from the base virtual atom::eval() ... and so on for everything that is an atom.
Even 'objects' such as variables are 'atom'. 'eval()' will simply return its value from a variant container held by the atom itself ( pointer, refering to the 'local' variant instance (the instance variant iself) held the 'atom' or to another variant held by an atom that is created in a given 'bloc/stack'. So 'atom' are 'inplace' instructions/objects.
As of now, as an example, chunk of not really meaningful 'code' as below just works:
r = 5!; // 5! : (factorial of 5 )
Response = 1 + 4 - 6 * --r * ((3+5)*(3-4) * 78);
if (Response != 1){ /* '<>' also is not equal op. */
return r^3;
}
else{
return 0;
}
Expressions ( arithemtics ) are built into binary tree expression:
A = b+c; =>
=
/ \
A +
/ \
b c
So the 'instruction'/statement for expression like above is the tree-entry atom that in the above case, is the '=' (binary) operator.
The tree is built with atom::r0,r1,r2 :
atom 'A' :
r0
|
A
/ \
r1 r2
Regarding 'full-duplex' mecanism between c++ runtime and the 'script' library, I've made class_adaptor and adaptor<> :
ex.:
template<typename R, typename ...Args> adaptor_t<T,R, Args...>& import_method(const lstring& mname, R (T::*prop)(Args...)) { ... }
template<typename R, typename ...Args> adaptor_t<T,R, Args...>& import_property(const lstring& mname, R (T::*prop)(Args...)) { ... }
Second: I know there are plenty of tools and libs out there such as lua, boost::bind<*>, QML, JSON, etc... But in my situation, I need to create my very own [edit] 'independant' [/edit] lib for "live scripting". I was scared that my 'interpreter' could take a huge amount of RAM, but I am surprised that it is not as big as using QML,jscript or even lua :-)
Thank you :-)
Don't bother with hacking a parser together by hand. Use a parser generator. lex + yacc is the classic lexer/parser generator combination, but a Google search will reveal plenty of others.
I am writing code to ingest the IOR file generated by the team responsible for the server and use it to bind my client to their object. Sounds easy, right?
For some reason a bit beyond my grasp (having to do with firewalls, DMZs, etc.), the value for the server inside the IOR file is not something we can use. We have to modify it. However, the IOR string is encoded.
What does Visibroker provide that will let me decode the IOR string, change one or more values, then re-encode it and continue on as normal?
I've already looked into IORInterceptors and URL Naming but I don't think either will do the trick.
Thanks in advance!
When you feel like you need to hack an IOR, resist the urge to do so by writing code and whatnot to mangle it to your liking. IORs are meant to be created and dictated by the server that contains the referenced objects, so the moment you start mucking around in there, you're kinda "voiding your warranty".
Instead, spend your time finding the right way to make the IOR usable in your environment by having the server use an alternative hostname when it generates them. Most ORBs offer such a feature. I don't know Visibroker's particular configuration options at all, but a quick Google search revealed this page that shows a promising value:
vbroker.se.iiop_ts.host
Specifies the host name used by this server engine.
The default value, null, means use the host name from the system.
Hope that helps.
Long time ago I wrote IorParser for GNU Classpath, the code is available. It is a normal parser written being aware about the format, should not "void a warranty" I think. IOR contains multiple tagged profiles that are encapsulated very much like XML so we could parse/modify profiles that we need and understand and leave the rest untouched.
The profile we need to parse is TAG_INTERNET_IOP. It contains version number, host, port and object key. Code that reads and writes this profile can be found in gnu.IOR class. I am sorry this is part of the system library and not a nice piece of code to copy paste here but it should not be very difficult to rip it out with a couple of dependent classes.
This question has been repeatedly asked as CORBA :: Get the client ORB address and port with use of IIOP
Use the FixIOR tool (binary) from jacORB to patch the address and port of an IOR. Download the binary (unzip it) and run:
fixior <new-address> <new-port> <ior-file>
The tool will override the content of the IOR file with the 'patched' IOR
You can use IOR Parser to check the resulting IOR and compare it to your original IOR
Use this function to change the IOR. pass stringified IOR as first argument.
void hackIOR(const char* str, char* newIOR )
{
size_t s = (str ? strlen(str) : 0);
char temp[1000];
strcpy(newIOR,"IOR:");
const char *p = str;
s = (s-4)/2; // how many octets are there in the string
p += 4;
int i;
for (i=0; i<(int)s; i++) {
int j = i*2;
char v=0;
if (p[j] >= '0' && p[j] <= '9') {
v = ((p[j] - '0') << 4);
}
else if (p[j] >= 'a' && p[j] <= 'f') {
v = ((p[j] - 'a' + 10) << 4);
}
else if (p[j] >= 'A' && p[j] <= 'F') {
v = ((p[j] - 'A' + 10) << 4);
}
else
cout <<"invalid octet"<<endl;
if (p[j+1] >= '0' && p[j+1] <= '9') {
v += (p[j+1] - '0');
}
else if (p[j+1] >= 'a' && p[j+1] <= 'f') {
v += (p[j+1] - 'a' + 10);
}
else if (p[j+1] >= 'A' && p[j+1] <= 'F') {
v += (p[j+1] - 'A' + 10);
}
else
cout <<"invalid octet"<<endl;
temp[i]=v;
}
temp[i] = 0;
// Now temp has decoded IOR string. print it.
// Replace the object ID in temp.
// Encoded it back, with following code.
int temp1,temp2;
int l,k;
for(k = 0, l = 4 ; k < s ; k++)
{
temp1=temp2=temp[k];
temp1 &= 0x0F;
temp2 = temp2 & 0xF0;
temp2 = temp2 >> 4;
if(temp2 >=0 && temp2 <=9)
{
newIOR[l++] = temp2+'0';
}
else if(temp2 >=10 && temp2 <=15)
{
newIOR[l++] = temp2+'A'-10;
}
if(temp1 >=0 && temp1 <=9)
{
newIOR[l++] = temp1+'0';
}
else if(temp1 >=10 && temp1 <=15)
{
newIOR[l++] = temp1+'A'-10;
}
}
newIOR[l] = 0;
//new IOR is present in new variable newIOR.
}
Hope this works for you.