How to convert a floating point value in exponential form to dot notation?

Question

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Prevent scientific notation in ostream when using << with double

I get 1e-1 as result after a computation how can I convert the result from exponent to dot notation i.e., 0.1 ? Why is it automatically converted to exponential notation!!

score 5 · Answer 1 · answered Aug 29 '10 at 17:42

5

You can use the fixed I/O manipulator to force the number to be printed in fixed-point notation:

double d = 42.0;
std::cout << std::fixed << d;

(std::scientific does the opposite: it forces the number to be printed in scientific notation)

answered Aug 29 '10 at 17:42

James McNellis

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I would like to save the value in double! – yesraaj Aug 29 '10 at 17:44
1

@yesraaj: What do you mean? 42.0 is 42.0 and how you format it for printing has no effect on the stored value. – James McNellis Aug 29 '10 at 17:45
I save the value into a database, where I use double being converted to appropriate NUMBER type in Oracle. – yesraaj Aug 29 '10 at 17:46
2

@yesraaj: Then it's oracle that has the problem, not C++ – Puppy Aug 29 '10 at 18:08

score 0 · Answer 2 · answered Aug 29 '10 at 23:01

Oracle (generally) doesn't do binary numbers (some support was added in 10g). Numbers are held in an internal format and, unless you use an implicit or explicit TO_CHAR, it is up to the "client" to display them (or any desired "prettifying").

select to_number('1e-1') num, 
       to_char(to_number('1e-1'),'9.9EEEE') sci_num, 
       to_char(to_number('1e-1')) std_num 
from dual;

            NUM SCI_NUM   ST
--------------- --------- --
            .10   1.0E-01 .1

How to convert a floating point value in exponential form to dot notation?

2 Answers2