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MathGroup Archive 2006

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Re: Converting decimal to/from IEEE hex format

  • To: mathgroup at smc.vnet.net
  • Subject: [mg71239] Re: [mg71206] Converting decimal to/from IEEE hex format
  • From: Carl Woll <carlw at wolfram.com>
  • Date: Sat, 11 Nov 2006 03:38:58 -0500 (EST)
  • References: <200611101138.GAA13743@smc.vnet.net>

Robert wrote:

>Can anyone tell me how to convert a number to/from the corresponding
>IEEE hex floating-point representation in either 32 or 64 bits in
>Mathematica?  For
>example, I would want to convert 1.0 into 3F800000 (32-bit) or
>3FF0000000000000 (64-bit), and vice-versa.  (When converting from
>decimal to hex, if the number is not exactly representable, I would
>want the nearest floating-point number.)  Thanks, Robert
>  
>
One idea is to use BinaryWrite and BinaryRead, although that requires 
the use of external files. Here is one implementation:

RealToHex32[x_Real?MachineNumberQ]:=Module[{tmp},
   tmp=OpenTemporary[BinaryFormat->True];
   BinaryWrite[tmp,x,"Real32"];
   tmp=Close[tmp];
   BaseForm[BinaryRead[tmp,"Integer32"],16]
]

In[31]:=
RealToHex32[1.0] // OutputForm
Out[31]//OutputForm=
3f800000
        16

The conversion backwards needs a design decision on what format you want 
the hex representation to be in.

Carl Woll
Wolfram Research


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