c++ - Error in displaying a double value in a PlainText widget -

[update]

this code:

double tmp=0;  double a=4.87149e+07; double b=10; double c=5.29e-06; ...  double sum=0; ofstream m2; m2.open("c:/capture/m2.doc"); (i=0;i<916;i++) {     (int j=0;j<916;j++)     {             tmp=a*b*c;             sum= sum+tmp;             m2 << sum << "\n";     } } 

'm having above:

when print sum, gives me nan result.

when omitted c sum formula, gives me non nan result. thus, believe compiler pretending it's +oo/-oo multiplication (a big, , c small), not case!

i,m dealing important data that.

i want print result @ end in textedit:

plaintextedit->setplaintext(qstring::number(sum)); 

as reach half of count loop (458), , j (458), values of sum become equal -1.#ind

how handle that?

running following:

#include <iostream> #include <fstream> #include <qdebug>  int main(int argc, char *argv[]) {     double tmp=0;      double a=4.87149e+07;     double b=10;     double c=5.29e-06;      double sum=0;     std::ofstream m2;     m2.open("m2.doc");     (int i=0;i<916;i++)     {         (int j=0;j<916;j++)         {                 tmp=a*b*c;                 sum= sum+tmp;                 m2 << sum << "\n";         }         qdebug() << sum;     } } 

yields: (lines 1-10 of m2.doc)

2577.02 5154.04 7731.05 10308.1 12885.1 15462.1 18039.1 20616.1 23193.2 25770.2 

... (lines 209760-209770) 209764 = 458 , j = 458

5.40555e+008 5.40558e+008 5.4056e+008 5.40563e+008 5.40566e+008 5.40568e+008 5.40571e+008 5.40573e+008 5.40576e+008 5.40579e+008 5.40581e+008 

... (lines 839047 839056 aka end)

2.16224e+009 2.16224e+009 2.16224e+009 2.16225e+009 2.16225e+009 2.16225e+009 2.16225e+009 2.16226e+009 2.16226e+009 2.16226e+009 

i opened file in notepad++ because ms word struggles such long files. tmp optimized compiler act constant: 2577.02, or if use printf can see additional precision pretty easily: 2577.018210 . qdebug() line yields similar answers terminal.

google's calculator output

double can keep track of huge range of values:

#include <limits> //... printf("%g\n", std::numeric_limits<double>::min()); printf("%g\n", std::numeric_limits<double>::max()); 

prints out

2.22507e-308 1.79769e+308 

with setup.

i hope helps.