[MLton-user] IEEEReal rounding not working

[Sean McLaughlin]

I meant the type should be

val roundFromString : IEEEReal.rounding_mode * string -> real option

On 7/27/07, Matthew Fluet <fluet at tti-c.org> wrote:
>
>
> On Fri, 27 Jul 2007, Sean McLaughlin wrote:
> > As for interval arithmetic, a main concern of mine is that
> > the sqrt function rounds correctly given the rounding mode, as specified
> > in IEEE754.
>
> The other aspect that I was wondering about was floating-point constants.
> That is, what should the following program do:
>
> val mtenth_lo = (down(); 0.1)
> val mtenth_hi = (up(); 0.1)
> val mtenth_near = (near(); 0.1)
> val mtenth_zero = (zero(); 0.1)
>
> val _ = print(word8vectorToString (P.toBytes mtenth_lo) ^ "\n")
> val _ = print(word8vectorToString (P.toBytes mtenth_hi) ^ "\n")
> val _ = print(word8vectorToString (P.toBytes mtenth_near) ^ "\n")
> val _ = print(word8vectorToString (P.toBytes mtenth_zero) ^ "\n")
>
>
> A very strict reading of The Definition says that special constants are
> evaluated as part of the dynamic semantics, yielding "a value according to
> normal mathematical conventions".  However, the function from special
> constants to values is:
>    val : SCon -> Val
> and the evaluation rule is:
>    E |- scon => val(scon)   (90)
> which suggests that the meaning of the special constants are not dependent
> upon the dynamic state.  On the other hand, the function from primitive
> functions and arguments to values is:
>    APPLY : BasVal * Val -> Val + Pack
> and the evaluation rule is:
>    E |- exp => b  E |- atexp => v  APPLY(b,v) = v'/p
>   ---------------------------------------------------
>    E |- exp atexp => v'/p
> which also suggests that primitives are pure functions, not dependent upon
> the dynamic state.  Since Real<N> arithmetic already steps outside of
> this, the question arises as to whether the evaluation of real constants
> should also step outside this.
>
>
>
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