Re: FP number syntax (was: ANN: DX-Forth 4.57)

In article <2024Dec25.123616@mips.complang.tuwien.ac.at>,
Anton Ertl <anton@mips.complang.tuwien.ac.at> wrote:

dxf <dxforth@gmail.com> writes:

On 25/12/2024 3:06 pm, John wrote:

And not sure how to enter decimals, I though maybe entering a ".0" after my numbers would flag them as reals not integers, but...
3.14  2.96  <return> does not put both numbers on the stack

>
Those would be illegal numbers - neither reals nor integers.

>
At least in standard Forth.  In traditional Forth 3.14 and 2.96 are
double-cell integers (with the value #314 and #296).  And backwards
compatibility demands that they should not be recognized as FP values.
>
In Gforth snapshots from the last few years (not available for CP/M,
sorry) you get the following when you type in "3.14":
>
*terminal*:2:1: warning: '3.14' is a double-cell integer; type `help' for more info ok 2
>
HELP then says:
>
To input floating-point numbers, use an exponent, e.g. "1e".
To input double-cell integers without warnings, use a base-prefix and put
the '.' only in the last position, e.g. "#1.".
>
But you can also do
>
' rec-float ' forth-recognize defer@ >stack
>
and then you can do things like
>
3.14 2.96 f* cr f.
>
which produces the following output:
>
*terminal*:18:1: warning: float without 'e' is non-standard
*terminal*:18:6: warning: float without 'e' is non-standard
9.2944  ok
>
You can also disable the warnings with "warnings off".
>
Followups set to comp.lang.forth.

A more simple approach is:
stick to case-sensitive.
In decimal 1E is a floating point number, as long as the floating
point number is loaded.
In HEX 1E is not a floating point number.
1e is not reconfignized anyhow, unless BASE is incremented a lot.

For hex instead use _ for the exponent sign.
1E_0 OK
.S
S[ ] OK
DECIMAL
.FS
3.000000000000000000E1

S[ ] OK

The advantage is that hex allows to represent floating point
numbers exactly.

(You guessed it, it is the ciforth way.)

>
- anton

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