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From: paquette@cpsc.ucalgary.ca (Trevor Paquette)
Newsgroups: comp.sources.wanted,comp.unix.wizards,comp.sys.sgi
Subject: Re: Float to sign/exp/mantissa
Summary: KEYWORD MISSING
Message-ID: <1046@cs-spool.calgary.UUCP>
Date: 5 Apr 89 18:04:01 GMT
References: <1026@cs-spool.calgary.UUCP> <1044@cs-spool.calgary.UUCP>
Sender: news@calgary.UUCP
Lines: 69

In article <1044@cs-spool.calgary.UUCP>, paquette@cpsc.ucalgary.ca (Trevor Paquette) writes:
> In article <1026@cs-spool.calgary.UUCP>, paquette@cpsc.ucalgary.ca (Trevor Paquette) writes:
] > 
] > 
] >    I am sure that someone out there has a routine that given
] > a floating point number, what is the sign, exponent and mantissa
] > of the number.. I'd rather not re-invent the wheel if this has
] > already been done. If some kind soul out there has such a
] > function, and is willing to send it my way, I'd be very grateful.
] >     
] >     aTdHvAaNnKcSe
] >         Trev
] > 
] 
]    Maybe I should elaborate on this a bit..
]     What I am doing is writing a Machine Independant Format (MIF) similar to
]  XDR that Sun has. This arose out of the fact that some of the machines
]  that we need to use do not have XDR support.. So I am writing my own.
]  Since floats and doubles are represented the same way on different machines

***
* The above line should read..                          
*>  Since floats and doubles are NOT represented the same way on different machines
* Sorry if the caused any confusion
***

]  I have to come up with a way of representing a number in a file that is
]  machine independant.
]     I DO NOT want to do something like the following to represent an integer..
] 
] /*      FILE *fp;
]        int num;    */
]       fprintf(fp,"%d ",num);
] 
]   This is clearly a waste of disk space.. when we can do the following..
] 
] /*      char ch[4]; */
] /*  to write the number */
]  ch[0] = (char)((*num & 0xff000000) >> 24);
]  ch[1] = (char)((*num & 0x00ff0000) >> 16);
]  ch[2] = (char)((*num & 0x0000ff00) >> 8);
]  ch[3] = (char)((*num & 0x000000ff));
]  fwrite(ch, 1, 4, fp);
] 
] /* to read the number */
]    fread(ch, 1, 4, fp);
]    num = (int)(ch[3]) + (int)(ch[2] << 8) + (int)(ch[1] << 16) + (int)(ch[0] << 24);
] 
]  Much better.. saves lotsa disk space.. files tend to be MUCH smaller this way.
] 
]   Now the problem arises when trying to save a float or a double.. how?
]  I want to keep as much precision in the number as possible.. 
] 
]     the following is a start but I still end up with a float to deal with..
]    
]    double d = some number;
]    double mant;
]    int exp;
] 
]    mant = frexp(d, &exp);
] 
]    I still have mant to deal with which is a float.. back to square one..
] 
]    Any help would be appreciated..

==============================================================================
               Trevor Paquette/GraphicsLand, Calgary, Alberta                 
 ..uunet!{ubc-cs,utai,alberta}!calgary!paquette          ICBM:51 03 N/114 05 W
 calgary!paquette@cs.ubc.ca      Luminous beings we are, not this crude matter