floating point precision
acehreli at yahoo.com
Wed Jan 11 16:06:10 PST 2012
On 01/11/2012 03:51 PM, dsmith wrote:
> How do you increase floating point precision beyond the default of 6?
> double var = exp(-1.987654321123456789);
> --> 0.137016
> Assuming this result is only an output format issue and that operations are
> still using double's 64 places, if var above is passed to a function, are all
> 64 places passed? Must it be passed by reference to make it so?
writefln takes a format argument. The following uses the actual
precision of the variable but it is wrong as it assumes (knows) that the
whole part of the result is zero. Since precision is the total of
significant digits, the digits after the period must be adjusted if the
whole part is not zero.
double var = exp(-1.987654321123456789);
auto fmt = "%." ~ to!string(var.dig) ~ "f";
Also check out "%e", "%g", and "%a"; some of which produce the same
output depending on the value.
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