Digest #170 2022-01-30


[218] 2022-01-28 10:17:58 DavidJones wrote:

referenceImplementation - Implement with ROT


I have a soft spot for the symmetry in this one.


[r782] 2021-11-23 08:10:12 AntonErtl replies:

example - New Line characters in a string passed to EVALUATE says

The set of conditions, if any, under which a "space" delimiter matches control characters is implementation defined.

So the standard makes no guarantees to programs wrt space-delimited parsing, with one exception: 11.3.5 says:

When parsing from a text file using a space delimiter, control characters shall be treated the same as the space character.

But AFAICS in EVALUATE, a standard system may choose to treat only BL as delimiter in that case, or it can also treat other control characters (including newline characters) as space delimiters. I recommend the latter.

When parsing with delimiters other than space (and none of the newline characters), the newline characters must be treated like any other non-delimiter. And when parsing with a newline character as delimiter, that character has to be treated as delimiter.

[r783] 2021-12-18 22:53:47 ruv replies:

requestClarification - Why "[" is specified using immediacy?

In most Forth systems the implemented interpretation semantics for [ are to do nothing. Probably in some systems they are to throw an exception.

And I don't have any idea how a program can rely to the former implementation variant. Could anybody provide a program example that has a benefit due to interpreting the word [ in interpretation state?

I can only imagine a situation when a user in REPL accidentally uses [ in interpretation state, and one system just interprets it without any side effects, but another shows an error message.

So a question is: why is one variant preferred over another?