MQL4 StringToDouble always returns zero - string

The function StringToDouble always returns zero on passing a variable string.
Let me demonstrate ...
This is what I have so far.
string balance = "12.50USD";
// lets extract the double only from the string
int x = StringReplace(balance,"USD",""); // now we have a plain number
Print(balance); // "12.50"
double balance_only = StringToDouble(balance);
Print(balance_only) ; // Zero? Why?
Well according to the documentation here and here
This is supposed to work? Right? What am I missing?
I even tried to add empty strings on the sides to trick the function but still
double b = StringToDouble(StringConcatenate("",balance,""));
Print(b); // Zero , Why :(
What seems to be the problem here?

After installing and unistalling a couple of MT4 instances,
It was there all along,
For some reason I was also using StringSplit function i.e
StringSplit(extracted_balance_string," ", &results[]);
Instead of
StringSplit(extracted_balance_string,StringGetCharacter(" ",0), &results[]); // the space was a special character
I missed that, my bad :D

Related

I am not sure how to fix the "TypeError: sequence item 1: expected str instance, int found" in my code?

I am having trouble with the second function in converting it back to the original string. I see what the issue is as when I call previous function, the tuple has a string and an int. So I assume I must convert that int to a string. But based on the code I wrote, I am not sure where to convert it. Hopefully, I am on the right track with this. My professor is very strict when it comes to certain things I cannot use any built-ins. Thank you. Any help is appreciated.
EDIT
Will put code back soon
My suggestion is in this case to use print statements for debugging.
def rldecode(rlencode):
decodedString = ""
L = []
for i in rlencode:
counter = 0
occurrence = i[1] # tuple (item, occurrence) == positions (0, 1)
for j in range(occurrence):
L.append(i[0])
return ''.join(L)

Arduino and TinyGPS++ convert lat and long to a string

I' m having a problem parsing the lat and long cords from TinyGPS++ to a Double or a string. The code that i'm using is:
String latt = ((gps.location.lat(),6));
String lngg = ((gps.location.lng(),6));
Serial.println(latt);
Serial.println(lngg);
The output that i'm getting is:
0.06
Does somebody know what i'm doing wrong? Does it have something to do with rounding? (Math.Round) function in Arduino.
Thanks!
There are two problems:
1. This does not compile:
String latt = ((gps.location.lat(),6));
The error I get is
Wouter.ino:4: warning: left-hand operand of comma has no effect
Wouter:4: error: invalid conversion from 'int' to 'const char*'
Wouter:4: error: initializing argument 1 of 'String::String(const char*)'
There is nothing in the definition of the String class that would allow this statement. I was unable to reproduce printing values of 0.06 (in your question) or 0.006 (in a later comment). Please edit your post to have the exact code that compiles, runs and prints those values.
2. You are unintentionally using the comma operator.
There are two places a comma can be used: to separate arguments to a function call, and to separate multiple expressions which evaluate to the last expression.
You're not calling a function here, so it is the latter use. What does that mean? Here's an example:
int x = (1+y, 2*y, 3+(int)sin(y), 4);
The variable x will be assigned the value of the last expression, 4. There are very few reasons that anyone would actually use the comma operator in this way. It is much more understandable to write:
int x;
1+y; // Just a calculation, result never used
2*y; // Just a calculation, result never used
3 + (int) sin(y); // Just a calculation, result never used
x = 4; // A (trivial) calculation, result stored in 'x'
The compiler will usually optimize out the first 3 statements and only generate code for the last one1. I usually see the comma operator in #define macros that are trying to avoid multiple statements.
For your code, the compiler sees this
((gps.location.lat(),6))
And evaluates it as a call to gps.location.lat(), which returns a double value. The compiler throws this value away, and even warns you that it "has no effect."
Next, it sees a 6, which is the actual value of this expression. The parentheses get popped, leaving the 6 value to be assigned to the left-hand side of the statement, String latt =.
If you look at the declaration of String, it does not define how to take an int like 6 and either construct a new String, or assign it 6. The compiler sees that String can be constructed from const char *, so it tells you that it can't convert a numeric 6 to a const char *.
Unlike a compiler, I think I can understand what you intended:
double latt = gps.location.lat();
double lngg = gps.location.lon();
Serial.println( latt, 6 );
Serial.println( lngg, 6 );
The 6 is intended as an argument to Serial.println. And those arguments are correctly separated by a comma.
As a further bonus, it does not use the String class, which will undoubtedly cause headaches later. Really, don't use String. Instead, hold on to numeric values, like ints and floats, and convert them to text at the last possible moment (e.g, with println).
I have often wished for a compiler that would do what I mean, not what I say. :D
1 Depending on y's type, evaluating the expression 2*y may have side effects that cannot be optimized away. The streaming operator << is a good example of a mathematical operator (left shift) with side effects that cannot be optimized away.
And in your code, calling gps.location.lat() may have modified something internal to the gps or location classes, so the compiler may not have optimized the function call away.
In all cases, the result of the call is not assigned because only the last expression value (the 6) is used for assignment.

How can I get an integer out of a String with sections

I try to get an integer (right after "PLAYING:STATION\nID:"out of the String shown in my screenshot by using the following code:
int zahl = Integer.parseInt(sentence.substring(sentence.indexOf("PLAYING:STATION\n
ID:")+1).trim());
But all I get is a NumberFormatException. How can I tell the trim()-method that it has to stop right after the number?
Screenshot of the complete String
Since you must select a specific ID: entry among several ones, I think the best way to proceed is using a regular expression. Using your output sample, I wrote the following code:
String text = "PLAYING_MODE\nID:\nPLAYING:STATION\nID:2\nNAME:wazee.org";
Pattern p = Pattern.compile("PLAYING:STATION\nID:(\\d+)");
Matcher m = p.matcher(text);
if (m.find()) {
int number = Integer.parseInt(m.group(1));
System.out.println(number);
}
which correctly parses the ID number that immediately follows PLAYING_STATION.
You could as well repeatedly work with the overloaded String.indexOf() method (find PLAYING:STATION, then the following ID:, then the following \n). I think the code might be harder to read, but it would still do the job.
I hope this will be helpful...
Cheers,
Jeff

assigning a string to a complex pointer

I'm trying to assign a string to an array defined like this
char *(*attributes)[][2]; as defined by a library I'm using.
I want to be able to put a string into attributes[i][0]
I think I'm just getting confused about the pointers, I'm getting errors saying invalid use of array with unspecified bounds.
The array of attributes is stored in a struct called info.
I've tried to access it as:
*(info->attributes)[i][0] = newAttributeName
which makes sense to me, but as I said, isn't working.
Any help would be greatly appreciated!
Since no one else is offering, I'd suggest:
char *attributesa[][2] = *attributes;
char *attributesb[2] = attributesa[0];
attributesb[0] = "Horsefeathers";
and then figure out how to turn that into one statement.
Here's the correct way, for future reference:
(*info->attributes)[i][0] = someString;
The trick is the parenthesis give precedence to info->attributes being dereferenced, because otherwise it will try to find [i][0] first.

Why does Processing think I'm passing an int into the color() function at the end of this code?

Preface: I'm working with Processing and I've never used Java.
I have this Processing function, designed to find and return the most common color among the pixels of the current image that I'm working on. the last line complains that "The method color(int) in the type PApplet is not applicable for the arguments (String)." What's up?
color getModeColor() {
HashMap colors = new HashMap();
loadPixels();
for (int i=0; i < pixels.length; i++) {
if (colors.containsKey(hex(pixels[i]))) {
colors.put(hex(pixels[i]), (Integer)colors.get(hex(pixels[i])) + 1);
} else {
colors.put(hex(pixels[i]),1);
}
}
String highColor;
int highColorCount = 0;
Iterator i = colors.entrySet().iterator();
while (i.hasNext()) {
Map.Entry me = (Map.Entry)i.next();
if ((Integer)me.getValue() > highColorCount) {
highColorCount = (Integer)me.getValue();
highColor = (String)me.getKey();
}
}
return color((highColor);
}
The Processing docs that I'm looking at are pretty sparse on the HashMap so I'm not really sure what's going on inside it, but I've been augmenting what's available there with Java docs they point to. But I'm not really grokking what's happening with the types. It looks like the key in the HashMap needs to be a string and the value needs to be an integer, but they come out as objects that I have to cast before using. So I'm not sure whether that's causing this glitch.
Or maybe there's just a problem with color() but the docs say that it'll take a hex value which is what I was trying to use as the key in the HashMap (where I'd rather just use the color itself).
Now that I've talked through this, I'm thinking that the color() function sees the hex value as an int but the hex() function converts a color to a string. And I don't seem to be able to convert that string to an int. I guess I could parse the substrings and reconstruct the color, but there must be some more elegant way to do this that I'm missing. Should I just create a key-value-pair class that'll hold a color and a count and use an arraylist of those?
Thanks in advance for any help or suggestions you can provide!
I'll dig deeper into this, but an initial thought is to employ Java generics so that the compiler will complain about type issues (and you won't get runtime errors):
HashMap<String,Integer> colors = new HashMap<String,Integer>();
So the compiler will know that keys are Strings and elements are Integers. Thus, no casting will be necessary.
I didn't figure it out, but I did work around it. I'm just making my own string from the color components like:
colors.put(red(pixels[i]) + "," + green(pixels[i]) + "," + blue(pixels[i]),1)
and then letting the function drop a color out like this:
String[] colorConstituents = split(highColor, ",");
return color(int(colorConstituents[0]), int(colorConstituents[1]), int(colorConstituents[2]));
This doesn't really seem like the best way to handle it -- if I'm messing with this long-term I guess I'll change it to use an arraylist of objects that hold the color and count, but this works for now.

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