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double to string ??

Started by malpass 11 replies 600+ views
Original Post
malpass
malpass
how do I convert a double to a string, itoa is for int but I dont know for doubles or floats etc..
Br1
Br1
how do I convert a double to a string, itoa is for int but I dont know for doubles or floats etc..

If you are using c++, take a look at boost''s lexical_cast lbrary
at boost.org.

Hope it helps
Bruno Martínez
Fruny
Fruny
iota() isn''t ANSI, only the char* → number conversion functions are.

In C, use sprintf().
In C++, use stringstream.


  
#include <sstream>
#include <string>

using namespace std;

int main()
{
   stringstream ss;
   double d = 415.234;
   string str;
   
   ss << d;
   ss >> str;
}
  



  
#include <stdio.h>

int main()
{
   char buf[256];
   double d = 415.234;
   
   snprintf( buf, 256, "%lf", d );
};


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malpass
malpass
nope, i havent got a clue wat that site is on about, it just looks a mess. I just want to know the line to convert a double to string, anyone. MSDN is never a help, I NEVER find what i''v after on there
Lektrix
Lektrix
I don''t know of a function that converts a double to a string, but I''m sure someone must of made one. I''ve heard of a function for converting floats to strings; you can just convert the double to float, depending on how much accuracy you need. Maybe you should just search for dtoa() or ftoa() on a search engine. Good luck.

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Arild Fines
Arild Fines
quote:
Original post by malpass
MSDN is never a help, I NEVER find what i''v after on there

But is that MSDN''s fault, or yours?


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malpass
malpass
well i tryed that stringstream and I got 6 errors, stringstream undeclared (the header is included), some errors about it not then finding the ss variable, << illegal left operand has type double, >> illegal righthand operand has type double etc...
malpass
malpass
fixed that, i missed using namespace, anyway, now its just displaying in int''s not float or double?
eldee
eldee
double mydouble = 9.1234567
char* mystring;

sprintf(mystring, "%d", mydouble);

cout << mystring << endl;

---------------------------------------------------
"9.1234567"

-eldee
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malpass
malpass
done it, it was showing ints because up above in my code I used atoi to convert the GetDlgItemText to doubles, which was actually converting them to int
civguy
civguy
quote:
Original post by eldee
double mydouble = 9.1234567
char* mystring;

sprintf(mystring, "%d", mydouble);

cout << mystring << endl;
You''d better allocate some memory.
dalleboy
dalleboy
Even better is to use the snprintf function instead of sprintf if it exists, and it usually does. It''s not standard C++ yet (it is standard in C99 though), but you''ll gain buffer length checking.


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IFooBar
IFooBar
all these are for converting double to string
1)ecvt() - Convert double to string of specified length
2)_fcvt() - Convert double to string with specified number of digits following decimal point
3)_gcvt() - Convert double number to string; store string in buffer

and if you want to makea float into a string then cast it to a double and use the above functions. You wont loose any precision that way.

I dont think the above functions are standard though. Search MSDN for parameter info.


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