Problem in double type value

[salirazataqvi]

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.

[kypa]

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.

[William Roeder]

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.

[salirazataqvi]

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