CODEWITHSUNDEEP
c
AmitM9S6
AmitM9S6

Reputation: 131

Convert a string with a double number on it, into a double number

I have the string temp[256] and inside it there's a double number, such as 0.125 and such, and everything is going well though some times it gets a number that's too big for a double number, like 0.888888888888888888888888888888888888888883, and the double number only holds like 7 numbers instead of all.

I've been using the atof to convert the string into the double, but I think the problem is the double here, because it doesn't have enough space for all the numbers.... This is what I wrote :

char temp[256]; // Has the number inside it
double temp_num = 0; // need to put the string inside this variable
temp_num = atof(temp);
printf ("%f\n", temp_num);

the output from the print is fine as long as the number isn't larger then 7 digits after the zero, but if it's a number like 0.8815818188888888888888888888888888888888888888888143, it only prints me the 7 first digits, like in this example it'll print 8815818 instead of the whole number... so I guess I need a bigger variable ?

Upvotes: 3

Views: 242

Answers (2)

ob_dev
ob_dev

Reputation: 2838

Printf have a default behavior of printing only 7 digits after the zero when dealing with doubles or floats however you can change that behavior and control how many numbers after the zero printf prints like this

printf ("%.20f\n", temp_num);

Here you get 20 digits after the zero.

For more details please refer to:

  1. http://www.cplusplus.com/reference/clibrary/cstdio/printf/
  2. The c programming language second edition.

Upvotes: 2

paulsm4
paulsm4

Reputation: 121599

Two issues:

1) I prefer "sscanf()" over "atof()": it allows you to check for conversion errors (i.e. illegal numbers).

2) As dirkgently already said, you can "format" any floating point value - restricting the #/digits,etc, with a "format string".

Upvotes: 1

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