Sollya User's Manual

Name:

precision returns the precision necessary to represent a number.

Library name:

sollya_obj_t sollya_lib_precision(sollya_obj_t)

Usage:

precision(x) : constant -> integer

Parameters:

x is a dyadic number.

Description:

precision(x) is by definition |x| if x equals 0, NaN, or Inf.
If x is not zero, it can be uniquely written as x = m*2^e where m is an odd integer and e is an integer. precision(x) returns the number of bits necessary to write m in binary (i.e. 1+floor(log2(m))).

Example 1:

   > a=round(Pi,20,RN);
   > precision(a);
   19
   > m=mantissa(a);
   > 1+floor(log2(m));
   19

Example 2:

   > a=255;
   > precision(a);
   8
   > m=mantissa(a);
   > 1+floor(log2(m));
   8

Example 3:

   > a=256;
   > precision(a);
   1
   > m=mantissa(a);
   > 1+floor(log2(m));
   1

See also: mantissa, exponent, round

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