Double to String in MQL5

Rmzy Krm Rmzy Abrahym 2018.03.24 23:02

Hi All,

i am trying to convert double to string in MQL5, the NormalizeDouble is such a failure as it get numbers such as 0.07000000000000001 and 0.9399999999999999

i have created the below function, but it can only filter our cases as 0.9399999999999999, but fails with 0.07000000000000001

double RNormalizeDouble(double val, int places){
   
   int index = StringFind(val, ".");
   
   string substring = StringSubstr(val, index, places+1);
   if(StringGetCharacter(substring, StringLen(substring)-1) == "0"){
      substring = StringSubstr(substring, 0, StringLen(substring)-2);
   }
   Print("Debug ",substring);
   string WholeNum = StringSubstr(val, 0, index-1);
   string res = WholeNum + substring;
   return StringToDouble(res);
}

Sample of the output

PN 0 00:52:30.450 Core 1 2017.01.02 06:24:41 A -0.9399999999999999

LM 0 00:52:30.450 Core 1 2017.01.02 06:24:41 Debug .93

FE 0 00:52:30.450 Core 1 2017.01.02 06:24:41 B -0.93

II 0 00:52:30.450 Core 1 2017.01.02 06:24:41 A -0.9399999999999999

JP 0 00:52:30.450 Core 1 2017.01.02 06:24:41 Debug .93

EN 0 00:52:30.450 Core 1 2017.01.02 06:24:41 B -0.93

MN 0 00:52:30.450 Core 1 2017.01.02 06:24:41 A -0.9399999999999999

RE 0 00:52:30.450 Core 1 2017.01.02 06:24:41 Debug .93

PD 0 00:52:30.450 Core 1 2017.01.02 06:24:41 B -0.93

EM 0 00:52:30.450 Core 1 2017.01.02 06:24:41 A -0.79

QL 0 00:52:30.450 Core 1 2017.01.02 06:24:41 Debug .79

LG 0 00:52:30.450 Core 1 2017.01.02 06:24:41 B -0.79

PG 0 00:52:30.450 Core 1 2017.01.02 06:24:41 A -0.63

JO 0 00:52:30.450 Core 1 2017.01.02 06:24:41 Debug .63

JP 0 00:52:30.450 Core 1 2017.01.02 06:24:41 B -0.63

NF 0 00:52:30.450 Core 1 2017.01.02 06:24:41 A -0.64

RG 0 00:52:30.450 Core 1 2017.01.02 06:24:41 Debug .64

EG 0 00:52:30.450 Core 1 2017.01.02 06:24:41 B -0.64

DO 0 00:52:30.450 Core 1 2017.01.02 06:24:41 A -0.34

EO 0 00:52:30.450 Core 1 2017.01.02 06:24:41 Debug .34

DD 0 00:52:30.450 Core 1 2017.01.02 06:24:41 B -0.34

DD 0 00:52:30.450 Core 1 2017.01.02 06:24:41 A -0.35

RM 0 00:52:30.450 Core 1 2017.01.02 06:24:41 Debug .35

GM 0 00:52:30.450 Core 1 2017.01.02 06:24:41 B -0.35

KR 0 00:52:30.450 Core 1 2017.01.02 06:24:41 A -0.06

HJ 0 00:52:30.450 Core 1 2017.01.02 06:24:41 Debug .06

NJ 0 00:52:30.450 Core 1 2017.01.02 06:24:41 B -0.06

FL 0 00:52:30.450 Core 1 2017.01.02 06:24:41 A -0.07000000000000001

QN 0 00:52:30.450 Core 1 2017.01.02 06:24:41 Debug .07

EG 0 00:52:30.450 Core 1 2017.01.02 06:24:41 B -0.07000000000000001

William Roeder 2018.03.24 23:12 #1

quantumninja: convert double to string in MQL5, the NormalizeDouble

Do NOT use NormalizeDouble, EVER. For ANY Reason. It's a kludge, don't use it. It's use is always wrong

Print out your values to the precision you want with DoubleToString - Conversion Functions - MQL4 Reference.
SL/TP (stops) need to be normalized to tick size (not Point.) (On 5Digit Broker Stops are only allowed to be placed on full pip values. How to find out in mql? - MQL4 and MetaTrader 4 - MQL4 programming forum) and abide by the limits Requirements and Limitations in Making Trades - Appendixes - MQL4 Tutorial and that requires understanding floating point equality Can price != price ? - MQL4 and MetaTrader 4 - MQL4 programming forum
Open price for pending orders need to be adjusted. On Currencies, Point == TickSize, so you will get the same answer, but it won't work on Metals. So do it right: Trailing Bar Entry EA - MQL4 and MetaTrader 4 - MQL4 programming forum or Bid/Ask: (No Need) to use NormalizeDouble in OrderSend - MQL4 and MetaTrader 4 - MQL4 programming forum
Lot size must also be adjusted to a multiple of LotStep and check against min and max. If that is not a power of 1/10 then NormalizeDouble is wrong. Do it right.

MathRound fails for one NormalizeDouble nn.nn9999999999 how to Design map for newbie

Rmzy Krm Rmzy Abrahym 2018.03.24 23:20 #2

Hi Whroeder1,

I saw this comment you type in another post, and i tried it already but didn't work, regardless look at the function again, i Do NOT use NormalizeDouble, clearly i am looking for an alternative in this MQL"5" not 4

anyway, thanks for passing by

EURUSD - Trends, Forecasts MAC - How can How to write a

nicholish en 2018.03.25 01:51 #3

whroeder1:
Do NOT use NormalizeDouble, EVER. For ANY Reason. It's a kludge, don't use it. It's use is always wrong

You really should stop spreading misinformation around here. What's wrong is your use of MathRound instead of NormalizeDouble in your rounding function since NormalizeDouble properly implements logic to prevent drift and MathRound does not (as pointed out by amrali in this thread).

Correct method:

double price = 1.2345678;
price = step * NormalizeDouble(price / step,0);

OP, you can use the CDouble lib make your life easy. :)

ea work fine for Can't round a number Libraries: CDouble & CDoubleVector

Rmzy Krm Rmzy Abrahym 2018.03.25 08:26 #4

nicholishen:

Correct method:

OP, you can use the CDouble lib make your life easy. :)

Hi Nicholishen,

I have tried the recommended function, but didn't work at all, even failed to pass any of the tests as below

double RNormalizeDouble(double num, double precision){      
     double c = 0.5 * DBL_EPSILON * num;
//      double p = MathPow(10, precision);  //slow
        double p = 1; while (precision--> 0) p *= 10;
        if (num < 0)
                p *= -1;
        return MathRound((num + c) * p) / p;
        
}

2018.03.25 10:24:03.126 Core 1 2017.01.02 08:37:40 A -0.8100000000000001

2018.03.25 10:24:03.126 Core 1 2017.01.02 08:37:40 B -0.8100000000000001

2018.03.25 10:24:03.126 Core 1 2017.01.02 08:37:40 A -0.82

2018.03.25 10:24:03.126 Core 1 2017.01.02 08:37:40 B -0.82

2018.03.25 10:24:03.126 Core 1 2017.01.02 08:37:40 A -0.6899999999999999

2018.03.25 10:24:03.126 Core 1 2017.01.02 08:37:40 B -0.6899999999999999

A tester without internet i Have added a Advice on a real

Alain Verleyen 2018.03.25 10:22 #5

Your topic is "double to string", what's wrong with DoubleToString() function ?

You should read and learn what is a double in mql.

Double-precision floating-point format - Wikipedia

en.wikipedia.org

Floating point is used to represent fractional values, or when a wider range is needed than is provided by fixed point (of the same bit width), even if at the cost of precision. Double precision may be chosen when the range and/or precision of single precision would be insufficient. In the IEEE 754-2008 standard, the 64-bit base-2 format is...

Rmzy Krm Rmzy Abrahym 2018.03.25 17:12 #6

Alain Verleyen:

Your topic is "double to string", what's wrong with DoubleToString() function ?

You should read and learn what is a double in mql.

Hi Alain,

I wrote the title this way as i convert it to String First, thanks for the note but i know what double and float are

anyway, my problem is actually with the precision of double as stated earlier

Any questions from newcomers Convert String Non-Numeric String ERROR in MQL NormalizeDouble()

Rmzy Krm Rmzy Abrahym 2018.03.25 17:20 #7

Alain Verleyen:

Your topic is "double to string", what's wrong with DoubleToString() function ?

You should read and learn what is a double in mql.

Dear Alain,

Could you advise if such values could affect the calculations ?

they might seem like infinitesimal yet it occurred to me that some trades fail because of wrong values like this due to unexpected precision, is that thought correct ?

Libraries: Math Utils Universal MA Cross EA looks iClose had old

Alain Verleyen 2018.03.25 17:30 #8

quantumninja:

Dear Alain,

Could you advise if such values could affect the calculations ?

they might seem like infinitesimal yet it occurred to me that some trades fail because of wrong values like this due to unexpected precision, is that thought correct ?

Forum on trading, automated trading systems and testing trading strategies

Double to String in MQL5

quantumninja, 2018.03.25 19:12

Hi Alain,

I wrote the title this way as i convert it to String First, thanks for the note but i know what double and float are

anyway, my problem is actually with the precision of double as stated earlier

Your question and all this topic shows that you don't understand what a double is. Some values can't be represented exactly as double, for example 0.1 can't.

There is no "wrong" values. nicholishen shows you the code to normalize a price.

Subtraction different double numbers problem identifying variable issue mql4

Rmzy Krm Rmzy Abrahym 2018.03.25 17:34 #9

Alain Verleyen:

Your question and all this topic shows that you don't understand what a double is. Some values can't be represented exactly as double, for example 0.1 can't.

There is no "wrong" values. nicholishen shows you the code to normalize a price.

Okay

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