Thoughts on IEEE P754

Sam Ruby rubys at
Thu Aug 21 19:08:13 PDT 2008

Waldemar Horwat wrote:
> Some tidbits about our embedding of decimal:
> - Contagion should be towards decimal if decimal and binary are mixed
> as operands.  5.3m + 1 should be 6.3m, not 6.3.  If we use 128-bit
> decimal, this also makes the behavior of heterogeneous comparisons
> (binary compared to decimal) sensible.

What should 5.3m + 1.0000000000000001 produce?

I also don't understand the heterogeneous comparisons comment.  What 
should 1.0000000000000001 == 1.0000000000000001m produce?

> - We should not print the trailing zeroes.  IEEE P754 does not
> require it, and it breaks things such as array lookup.  There is
> precedence for this in ECMAScript:  -0 and +0 both print as "0".  If
> someone really wants to distinguish among equal numbers, he can do it
> with a function call to one of the mandated functions.

Please explain the breakage?

When dealing with currency, having 0.05 + 0.05 produce 0.10 is a feature.

- Sam Ruby

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