precision problem with double

[6000351]

Hello,

double OrderSizeArr[3] ;

OrderSizeArr[0]=0.05; 

//SignalSize function type is double, SignalSize(1)=0.10 and SignalSize(2)=0.14

OrderSizeArr[1] = MathCeil(((SignalSize(2)/SignalSize(1))) * (OrderSizeArr[0] * 100)) / 100; 

OrderSizeArr[2] = MathCeil(((float)(SignalSize(2)/SignalSize(1))) * (OrderSizeArr[0] * 100)) / 100;

Alert(OrderSizeArr[1]," - " , OrderSizeArr[2]);

the result for the above code is 0.08 - 0.07000000000000001

but it should be 0.07 - 0.07

()

what is the problem and how can I fix it?

I tried  NormalizeDouble but it didn't work

I changed OrderSizeArr type to float and it worked, but kept giving a warning , so I changed it back to double.

thank you 

[William Roeder]

6000351:

the result for the above code is 0.08 - 0.07000000000000001

I tried  NormalizeDouble but it didn't work

You used NormalizeDouble, It's use is usually wrong, as it is in your case.

1. 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 programming forum

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

3. SL/TP (stops) need to be normalized to tick size (not Point) — code fails on metals. (On 5Digit Broker Stops are only allowed to be placed on full pip values. How to find out in mql? - 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 programming forum

4. 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 programming forum or Bid/Ask: (No Need) to use NormalizeDouble in OrderSend - MQL4 programming forum

5. 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.

6. MathRound() and NormalizeDouble() are rounding in a different way. Make it explicit.
             MT4:NormalizeDouble - MQL5 programming forum
             How to Normalize - Expert Advisors and Automated Trading - MQL5 programming forum

7. Prices you get from the terminal are already normalized.

8. PIP, Point, or Tick are all different in general.
             What is a TICK? - MQL4 programming forum 2014.08.03

[6000351]

William Roeder:
You used NormalizeDouble, It's use is usually wrong, as it is in your case.

1. 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 programming forum

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

3. SL/TP (stops) need to be normalized to tick size (not Point) — code fails on metals. (On 5Digit Broker Stops are only allowed to be placed on full pip values. How to find out in mql? - 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 programming forum

4. 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 programming forum or Bid/Ask: (No Need) to use NormalizeDouble in OrderSend - MQL4 programming forum

5. 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.

6. MathRound() and NormalizeDouble() are rounding in a different way. Make it explicit.
             MT4:NormalizeDouble - MQL5 programming forum
             How to Normalize - Expert Advisors and Automated Trading - MQL5 programming forum

7. Prices you get from the terminal are already normalized.

8. PIP, Point, or Tick are all different in general.
             What is a TICK? - MQL4 programming forum 2014.08.03

thank you for your answer 

I understand the problem now but I still don't know exactly how to fix it

I don't just want it to be printed out, I want to use it as lot size, so DoubleToString will not fix the problem

if you could just tell me exactly what changes do I have to do to get the code to work right

thank you again