Comparsion Problem | Forex Factory

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Comparsion Problem

  • #1
  • First Post: Jun 21, 2007 5:02pm Jun 21, 2007 5:02pm
Hello,
i try to compare two double numbers with the same values but the querie is false

Inserted Code
double a,b;
 
a=High[i]-Open[i]; //The Result is 0.0001
b=1.3333-1.3332; //The Result is 0.0001
 
 
if(a==b)Print("true"); //Result is false
if(a>b)Print("true"); //Result is true
if(a<b)Print("true"); //Result is false
What ist the problem please, why does this dont match?
How is the solution?
  • #2
  • Jun 21, 2007 6:09pm Jun 21, 2007 6:09pm
Quoting Heino
Hello,
i try to compare two double numbers with the same values but the querie is false

Inserted Code
double a,b;
 
a=High[i]-Open[i]; //The Result is 0.0001
b=1.3333-1.3332; //The Result is 0.0001
 
 
if(a==b)Print("true"); //Result is false
if(a>b)Print("true"); //Result is true
if(a<b)Print("true"); //Result is false
What ist the problem please, why does this dont match?
How is the solution?
Apparently the result of a is not exactly 0.0001. Sometimes there may be digits in the price beyond what is shown. With OANDA, there is, I don't know about the platform/broker you are using.
  • #3
  • Jun 21, 2007 7:13pm Jun 21, 2007 7:13pm
Hello, i use the Metatrader platform and code with mql4 script language.
  • #4
  • Jun 21, 2007 7:16pm Jun 21, 2007 7:16pm
Quoting Heino
Hello,
i try to compare two double numbers with the same values but the querie is false

Inserted Code
double a,b;
 
a=High[i]-Open[i]; //The Result is 0.0001
b=1.3333-1.3332; //The Result is 0.0001
 
 
if(a==b)Print("true"); //Result is false
if(a>b)Print("true"); //Result is true
if(a<b)Print("true"); //Result is false
What ist the problem please, why does this dont match?
How is the solution?
Instead of using High[i] try

NormalizeDouble(High[i],Digits)

Use the same for Open[i]

HTH
Stubbornly persistent
  • #5
  • Edited 9:13pm Jun 21, 2007 8:51pm | Edited 9:13pm
Hello, i have try it with NormalizeDouble() and very happy that can tell you it works, this function have neutral the double values and now the queries with if are true, thank you very much, god bless you all :-).
  • #6
  • Jun 21, 2007 10:44pm Jun 21, 2007 10:44pm
  •  tesla
  • | Joined Oct 2006 | Status: Friendly Neighborhood Programmer | 533 Posts
Exactly correct. When working with floating-point (non-integer) values there's no such thing as exact precision.

double dValue = 1 / 10;

You'd expect dValue to equal 0.1, right? It can't. Most likely it's equal to something like 0.100000000000034. It's complicated to explain but google "floating-point precision" or check out this entry in wikipedia.

The proper way to handle this is to ALWAYS use the NormalizeDouble(...) function when you're evaluating a non-integer value.

ALWAYS.
  • #7
  • Jun 22, 2007 5:44am Jun 22, 2007 5:44am
Yes thank you for very well explanation to.
  • #8
  • Jun 22, 2007 6:21am Jun 22, 2007 6:21am
hello
  • #9
  • Last Post: Jun 22, 2007 8:31am Jun 22, 2007 8:31am
Quoting tesla
Exactly correct. When working with floating-point (non-integer) values there's no such thing as exact precision.

double dValue = 1 / 10;

You'd expect dValue to equal 0.1, right? It can't. Most likely it's equal to something like 0.100000000000034. It's complicated to explain but google "floating-point precision" or check out this entry in wikipedia.

The proper way to handle this is to ALWAYS use the NormalizeDouble(...) function when you're evaluating a non-integer value.

ALWAYS.
Yeah, that! I remember learning this waaaaaay back when, but didn't remember or never knew the exact specifics or why, and didn't know if computers were still that way or not, so I didn't say it. Thanks for the tip, Tesla!
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