[Haskell-cafe] Re: FFI to double constants, printf

That helps, but: #include #include int main () { long double d = HUGE_VAL; printf("%.30Lf\n", d); } still prints just (as it should, I think): inf Is there maybe some way to check if a double or long double do have a "proper" value?

You probably want something like printf("%.10Lg",d);. Here's a shot C example and its output:

#include

int main(int argc, char * argv[]) { long double d = 0.123456789;

printf("%.30Lf\n", d); printf("%.20Lg\n", d); printf("%.20Le\n", d); }

/* 0.123456788999999997336054491370 0.12345678899999999734 1.23456788999999997336e-01 */

On Fri, Jul 17, 2009 at 6:41 PM, Maurí­cio wrote:

...

When we printf doubles from C (like when using hsc2hs to bind to a constant) we can get something that's not valid Haskell. See these 2 examples:

3.40282347e+38F

inf

Do you know some way to printf a double using printf (or any other standard function) that's always going to give me valid Haskell text, even in special cases?

Thanks, Maurício

_______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe