acosl
long double acosl(long double);
extern long double acosl(long double);
extern long double acosl(long double);
extern long double acosl(long double);
LD_RE(ans) = acosl(x);
LD_RE(ans) = acosl(x);
LD_RE(ans) = (hx >= 0)? acosl(B) : acosl(-B);