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# precision in C

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## precision in C

(OP)
Hello everyone,

I need to be able to limit(or control) precision of double datatype to 10 decimal places and not more or less. How would i do it? I can also use float or any other datatype, the issue is making precision only 10 decimal places:

0.0123456789

and this is not output formatting.... I am working with a program that does a scientific computation, so precision is important in calculations, not for the display.

Thank you in advance.

### RE: precision in C

Guess you need to work in a language like Coral66, Ada or Cobol where the number of decimal places can be fixed.

Assuming fmod behaves the same way as % and that they haven't done it properly for -ve numbers, after each calculation, you could do something like

#### CODE

x -= fmod (x, 1E-10);
Very expensive though.

### RE: precision in C

(OP)
thank you for the idea! it works!

### RE: precision in C

Neat!

EvLer,

If the number is greater than or equal to 1 ( or less than 0.1) how should it be rounded?  For example, does

1.12345123451 get rounded to
1.1234512345  (10 digits after decimal) or
1.123451234   (10 significant figures) ?

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