
Boost : 
From: k.hagan_at_[hidden]
Date: 20010212 09:05:38
On the subject of providing constants in float, double and long
double flavours...
1 x86 family processors have builtin constants for pi and several
logarithms which are accurate to 66 bits. (This is 2bits more
than a register.) A compiler might provide
#define PI __pi__
where __pi__ tells the code generator to use a fldpi instruction
rather than loading a value from memory. Does the desirability of
this implementation option restrict our choice of syntax, or can
compilers work equally happily with
namespace math_constants {
inline long double pi() { return __pi__; }
}
2 The same processors also typically have no loss in performance
if asked to evaluate expressions at full precision instead of a
more reduced precision. If a compiler vendor used the same over
precise value for all three common floating point types, perhaps
using the "__pi__" trick for all three, would this conform to our
expectations?
Boost list run by bdawes at acm.org, gregod at cs.rpi.edu, cpdaniel at pacbell.net, john at johnmaddock.co.uk