Returns normalized value of the double type.Īlert( "a=", DoubleToStr( NormalizeDouble(a, 5), 8)) The function NormalizeDouble (double value, int digits) rounds the floating point value to the given precision. The program will print -324, but we have to take into account the decimal digits in fraction (+15) and we will get an approximate value for the exponent of the smallest double number. Let's try to estimate the smallest exponent of the double number.
The range of possible values for the double numbers is much wider: from -1.7*e-308 to 1.7*e308. The constants of the double type are stored in memory in a similar way as double variables, therefore it is necessary to take into account the limit of 15 significant digits in their definition.īut do not confuse the accuracy of the decimal digits precision with the calculation precision for the double numbers. It seems that finally we can expect that a=1.Īlert( " a=",DoubleToStrMorePrecision(a, 16)) In the next cycle (j), we are dividing the resulted value a by all of the integers from 23 to 2. The result is stored in the variable a of double type. In the first cycle (i) we are calculating the factorial of 23 (product of the integers from 2 to 23), and the result is: 23!=25852016738884976640000. To illustrate this fact, let's consider the following example. The accuracy of the decimal digits storage in computer is dependent on the fraction size and limited by 52 bits. Accuracy of the decimal digits precisionīecause of the double precision floating-point format there is a limited accuracy of their storage.įor example, if we assume that we have an unlimited precision, as in theory, for any double numbers A and B, the following expressions are always valid: In some cases to show the numerical values of double numbers (for example, in Print, Alert, Comment) it is better to use the functions DoubleToStrand DoubleToStrMorePrecision (from stdlib.mq4) to display more precise values, instead of the standard 4 digits output precision.Īlert( "Standard output=",a, ", More precise output=",DoubleToStrMorePrecision(a, 15)) It will allow to save time in searching for possible errors.ĭouble a = 2.0 / 3 Alert ( "Standard output:" ,a, ", 8 digits precision:", DoubleToStr (a, 8 ), ", 15 digits precision:", DoubleToStrMorePrecision (a, 15 ) ) return( 0) Values of double numbers to the specified precision. Standard library stdlib.mq4, which allows you to control the numerical Verify the calculation results and to debug you can use the function DoubleToStrMorePrecision(double number, int precision) of
In this note we will consider a typical programming errors, that occurs while working with double numbers in MQL4 programs.
Mathmod mql4 code#
In the most of cases, the careful analysis shows that the language andĬompiler work correctly, but code has a small error, and it can They are checking the code again and again, finding the new "mistakes" in language, in implementation, in functions, etc.
The program is compiled and can work, but not as it should. The results of some mathematical calculations differ from thoseĮxpected. Many newbies often have some questions when When we are writing an Expert Advisor for trading, we must be sure that it will work correctly. The MQL programming opens new opportunities for the automated trading, many people all over the world already have appreciated it.
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