Re: Some modules from Modula-2

[acken@informatik.uni-kl.de]

Mike wrote:
>  I would be interested in seeing the original modules you defined to
>  implement RealStr/Conv.  
They're gone a long time ago.  Should now be in bit hell.

>  It is possible to precisely represent
>  REAL/LONGREAL numbers since this was also required for the Math(L)
>  modules.  I mapped the required bit patterns into an integer and
>  then interpreted these integers as REALs or LONGREALs.  Some numbers
>  such as 0.5, 0.25, 0.75, 1.0, etc. are exactly representable so they
>  shouldn't cause any conversion problems.  Of course, numbers like 0.1
>  are not exactly representable because they end up being numbers like
>  3DCCCCCD (REAL) or 3FB999999999999A (LONGREAL).  Note the rounding up
>  of the last hexadecimal digit since these numbers repeat the `C' or `9'
>  patterns forever.
The idea is to get as close an approximation as possible.  When
converting a string to real and the floating-point representation is,
say, X, then both succ(X) and pred(X) shouldn't be close to the
intended conversion.  succ(X) (pred(X)) are the next larger (smaller)
floating point value to X.

-- mva