Re: fixed point vs floating point

[dewar@merv.cs.nyu.edu (Robert Dewar)]

Seymour J says

<<BTW, very few real programs have constructs like
constant+constant/constant; usually at least one term will be a
variable. Use default precision in the statement

        A = 1 + B/3;

and the "problem" disappears?
>>

Maybe and maybe not. Depending on the scale and precision of B, you may
prefer to write

        A = 1 + B/03;

which has different semantics. I find changing the number of leading zeroes
in a decimal constant to be a non-intuitive way of controlling the scale
and precision of the intermediate result, and I think it is FAR safer to
make the programmer think explicitly about what scale and precision is
required, define a type that encapsulates this decision, and write

        A := 1 + Inttype (B / 3.0);

Yes, it requires more work from the programmer, but only work that really
is quite necessary. Fixed-point requires manual scaling, which is why
people prefer floating-point. To think that fixed-point semantics can
be effectively automated so it really functions as a poor man's floating-
point where everything is done right automatically is, I am afraid, naive.