[perl #41202] text->float conversion gives wrong answer

On Sun Jan 07 10:45:52 2007, zefram@fysh.org wrote:
> $ perl -lwe 'printf "%f\n", 1180591620717411303424.0'
> 1180591620717411172352.000000
> $
> 
> The value that I put in the source is exactly 2^70.

Perl’s atof implementation (c2988b20) multiplies by ten every time it
scans a new digit. This results in loss of precision. What is the best
way to tell whether an NV differs from the PV it was derived from?
Running it through sprintf internally seems like a bit much.

• [perl #41202] text->float conversion gives wrong answer by Father Chrysostomos via RT