Problem in double type value

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Hi all,

I am using BollingerBand in MQL5. When I copy values in buffer using CopyBuffer function, I got Un-Normalized values, which contains  more then five decimal places. Moreover I explicitly tried to normalized them using NormalizeDouble and DoubleToString methods but both of them some time works fine but some time don't work.


I also use StringSubstr to get 5 or 3 decimal places depending on currency and append it with the part before decimal places but as soon as i put it in double variable it automatically append digits in it. for example:


1. initial value: 87.82087843203483

2. As it was AUDJPY pair, I picked till 3 digits after decimal: 87.820

3. Then I assign it double type variable and it becomes: 87.81999999999999

Why the datatype automatically rounding the value.


Please help.

 

Doubles and floats are not stored as exact values and normalization doesn't change that. Best to use calculated values for further calculations and StringSubstr(DoubleToString()) for human-readable output.

Also calculated float/double == other calculated float/double doesn't work, MathAbs(calculated double-calculated double))<0.000001 or something like that should be used.
 
Floating point has infinite number of decimals, it's your not understanding floating point and that some numbers can't be represented exactly. (like 1/10.)
          Double-precision floating-point format - Wikipedia, the free encyclopedia

See also The == operand. - MQL4 and MetaTrader 4 - MQL4 programming forum

Print out your values to the precision you want with DoubleToString - Conversion Functions - MQL4 Reference.

 
whroeder1:
Floating point has infinite number of decimals, it's your not understanding floating point and that some numbers can't be represented exactly. (like 1/10.)
          Double-precision floating-point format - Wikipedia, the free encyclopedia

See also The == operand. - MQL4 and MetaTrader 4 - MQL4 programming forum

Print out your values to the precision you want with DoubleToString - Conversion Functions - MQL4 Reference.

Thanks for your reply, please tell me if I want less presize value for example up to 5 decimal places then what data type should I use to store it. Thanks

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