Re: Number parsing with checks

On 2024-10-12 05:45, dxf wrote:

The basics:
 : .BAD ( -- )  cr ." Invalid item"  .abort ;
 : ZE? ( x -- )  if .bad then ;     \ abort if non-zero
: NZ? ( x -- )  0= ze? ;           \ abort if zero

Typically, if word name ends with a question mark, the first (top) output parameter of the word is a *flag*. And it's true for all standard words. (though, opposite is not true)
These are better names and narrower stack diagrams:
   DROP-NZ ( x\0 --  |  0 -- never )
   DROP-ZE ( 0 --  |  x\0 -- never )

: ?ZE ( x -- x )  dup ze? ;        \ check x is zero
: ?NZ ( x -- x )  dup nz? ;        \ check x is non-zero

Better stack diagrams:
   ?ZE ( 0 -- 0  |  x\0 -- never )
   ?NZ ( x.some\0 -- x.some  |  0 -- never )
I suggest to use the data type symbol "never" for the empty data type.
See my explanation about the empty data type at <https://github.com/ForthHub/discussion/discussions/171#discussioncomment-10882259>
(this can be discussed there, or in a new thread here)
--
Ruvim