realprecision

Function: _def_realprecision
Class: default
Section: default
C-Name: sd_realprecision
Prototype:
Help:
Doc: the number of significant digits used to convert exact inputs given to
 transcendental functions (see \secref{se:trans}), or to create
 absolute floating point constants (input as \kbd{1.0} or \kbd{Pi} for
 instance). Unless you tamper with the \tet{format} default, this is also
 the number of significant digits used to print a \typ{REAL} number;
 \kbd{format} will override this latter behavior, and allow you to have a
 large internal precision while outputting few digits for instance.

 Note that PARI's internal precision works on a word basis (by increments of
 32 or 64 bits), hence may be a little larger than the number of decimal
 digits you expected. For instance to get 2 decimal digits you need one word
 of precision which, on a 64-bit machine, actually gives you 19 digits ($19 <
 \log_{10}(2^{64}) < 20$). The value returned when typing
 \kbd{default(realprecision)} is the internal number of significant digits,
 not the number of printed digits:
 \bprog
 ? default(realprecision, 2)
       realprecision = 19 significant digits (2 digits displayed)
 ? default(realprecision)
 %1 = 19
 @eprog
 The default value is \kbd{38}, resp.~\kbd{28}, on a 64-bit, resp.~32-bit,
 machine.