[Amforth-devel] >FLOAT

[Leon N M. <leo...@gm...>]

Ok, I've added a very rough version of >FLOAT, which takes the address and 
length of a string and returns a float.

For example, here's an 8 character long string starting at address 471 -- first 
displayed using TYPE, then converted to a float and printed with FS.

> 471 8 type
46.3e-42 ok
> 471 8 >float fs.
4.6298862E-41  ok

It's not so accurate (and it's slow) because it's using some floating point 
arithmetic where integer arithmetic will do, but I'll deal with that later (I 
even hope to use a nice conversion algorithm, like 
<http://portal.acm.org/citation.cfm?id=368376>).

Two things:

1) How does exception handling work? >FLOAT is supposed to return FALSE if 
it's can't convert something to a string, but currently it will just throw an 
error because NUMBER will throw an error (since NUMBER is used under the 
hood). I'd like to catch any error NUMBER throws and then return FALSE as 
required.

2) Currently NUMBER accepts numbers with a leading negative sign, but not a 
leading positive sign (e.g. -101 works, but +101 causes an error). ANS94 
requires floats to work with both, so it would be easier for me if NUMBER works 
with both. (Does ANS94 say anything about accepting positive signs for 
integers?)

-Leon