Description

X'Machine_Mantissa is an Ada attribute where X is any floating point type.

Floating point types are represented as:

${\displaystyle sign\times mantissa\times radix^{exponent}}$

where

sign is 1 or -1

mantissa is a fraction in base radix

radix is the hardware radix (usually 2)

exponent is an integer

'Machine_Mantissa returns the maximum number of digits in the mantissa.

Example

with Ada.Text_IO;

procedure Machine_Mantissa is

   package T_IO renames Ada.Text_IO;
   package I_IO is new  Ada.Text_IO.Integer_IO (Integer);
begin
   T_IO.Put ("Mantissa of Float type       = ");
   I_IO.Put (Float'Machine_Mantissa);
   T_IO.New_Line;
   
   T_IO.Put ("Mantissa of Long_Float type  = ");
   I_IO.Put (Long_Float'Machine_Mantissa);
   T_IO.New_Line;

end Machine_Mantissa;

The output with GNAT 4.6 on the x86-64 architecture is:

Mantissa of Float type       =          24
Mantissa of Long_Float type  =          53

See also