CODEWITHSUNDEEP
c++floating-point
user189320
user189320

Reputation:

How to print full float numbers instead of "1.01383e+007"?

I want to print out the full legitimate value of some large summation of floats, but when floats are large enough you get this notation such as "1.01383e+007". How can you get the legitimate value?

Upvotes: 4

Views: 4516

Answers (4)

David Heffernan
David Heffernan

Reputation: 612794

I read your question to mean that you do not want to output scientific format. If so then you can control the stream formatting like this:

cout << setiosflags(ios::fixed) << thefloat << endl;

Upvotes: 7

Lie Ryan
Lie Ryan

Reputation: 64827

you'll need to use a decimal library, e.g. gmp; the "1.01383e+007" format are due to the way float are stored.

Upvotes: 0

wallyk
wallyk

Reputation: 57764

An important characteristic of floating point is that they do not have precision associated with all the significant figures back to the decimal point for large values. The "scientific" display reasonably reflects the inherent internal storage realities.

If you want 10138300 (for example) to appear, use a datatype which has more significant figures, such as double in the C family languages for values up to 1015 or so. Or use an extended precision integer representation, such as long or long long depending on the CPU architecture and programming language or environment.

Upvotes: 3

WSBT
WSBT

Reputation: 36323

The float data type does not store the precise value, and hence it is not possible to print out the exact value.

In a float, 32 bits are divided between three distinct parts: The sign bit, the exponent and the mantissa like: S EEEEEEEE MMMMMMMMMMMMMMMMMMMMMMM

In simpler terms, instead of storing the precise "12345678", float data type will only store "1.23*10^7" (and double data type will store "1.2345*10^7"). Other digits are lost.

Maybe you can look into the "Big Integer" library in C++ if you are interested in the precise value of a large number.

Upvotes: 0

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