how to convert a floating point into a string

Question

How to convert a floating point into a string and add the 2 decimals when the floating point is a round number. Currently I am using the following, but for round numbers, I would like to have the .00 added. Do I need to write my own routine for that?

float floatingNumber = 1.00;
string string;
ostringstream stream;

stream << floatingNumber;
string += stream.str(); // result is 1 not 1.00

`float floatingNumber = 1.00;` is identical to `float floatingNumber = 1;` — David Heffernan, May 16 '13 at 08:36
possible duplicate of [Precise floating-point<->string conversion](http://stackoverflow.com/questions/1311242/precise-floating-point-string-conversion) — Joris Timmermans, May 16 '13 at 08:44
@MadKeithV: Similar, but that is not the same issue. It deals with the (mathematically real) difference between 1.34 and 1.340000000001. This deals with the (mathematically non-existent) difference between 1 and 1.00. — MSalters, May 16 '13 at 09:57

ForEveR · Accepted Answer · 2013-05-16T08:41:40.927

7

You should set precision manually and use flag, that allows you to use fixed notation

setprecision fixed

stream << std::fixed << std::setprecision(2) << floatingNumber;

edited May 16 '13 at 08:41

answered May 16 '13 at 08:36

ForEveR

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Thanks for that, howver my compiler says that setprecision is not a member of std. Is my compiler too old (borland c++ 6.0). – Michel de Man May 16 '13 at 09:01
@MicheldeMan How about check links? `#include ` will fix your problem. – ForEveR May 16 '13 at 09:07

Cyril Leroux · Answer 2 · 2013-05-17T09:24:01.443

1

if you are using c++11, you can convert a float to std::string using std::to_string()

float f(0.5f);
std::string str = std::to_string(f);

Same thing using auto :

auto f(0.5f); // f is a float
auto str = std::to_string(f); // str is a std::string

However, you'll have to handle the precision manually.

edited May 17 '13 at 09:24

answered May 17 '13 at 09:18

Cyril Leroux

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how to convert a floating point into a string

2 Answers2