NOT operator

[grimblefritz]

While the complement "~(expression)" feature is good, it is syntactically ugly - especially in more complex queries. I would like to see a NOT operator as it would make expressions simpler to write and read. I think the best choice is to use the bang (!) to negate the following expression:

!name
name!=value

This would allow expressions such as:

!compute && type!=admin && mem=64

rather than:

~(compute || type=admin) && mem=64

As I said earlier, I believe the benefit becomes more apparent as the complexity of the query increases.

[chu11]

I will admit that some of the tokens are non-optimal. They were selected based on what characters & symbols users were already commonly using in genders. Although I cannot recall why, some users were using a ! sign already for some purpose.

But perhaps this should be revisited.

[grimblefritz]

Well... that could be alleviated by allowing quoted values:

name="value"

but that's a whole 'nother can of worms! (And even more overhead in parsing.)

Perhaps a --compat flag that would use the old-style parsing?

[wlschwartz]

Thanks, Grimble! This and your other submissions all look like strong suggestions. Let's see it happen!

[elstak]

Why using the Polish notation only for the negation operator? I can understand it may be simple to implement, but it makes not consistent with the rest of infix operators.

[grimblefritz]

My usage of genders is based primarily on nodeattr. I don't find the proposed use of "!" to be inconsistent with shell conventions. Certainly a "not equal" operator is common to most languages, and !expression is equivalent to "not expression" and also "if ! [ test ]" in shell. Perhaps it is inconsistent with a textbook definition of infix operators, but it seems very consistent with the typical callers of nodeattr.

Also, I think simple is in keeping with the design objectives of genders.