Keyword for readonly modifiers

[ethers]

Looking across contracts, it appears that most modifiers don't change state: they're generally used for checking preconditions and "condition-orientated" programming. IMO this is good since they are kept simple, and since they don't change state, their order doesn't matter. So instead of the term modifier, as a starting point how about another (additional) keyword for them? The cases where people are changing state in a modifier can remain the same and use modifier, but for new contracts where they don't change state, a term other than modifier seems more fitting as the contract isn't getting modified.

Some suggestions are condition, precondition, pre. Other languages from https://en.wikipedia.org/wiki/Design_by_contract could be consulted for other potential names.

[VoR0220]

hmmm...interesting proposal. pure modifier?

[axic]

I was thinking about allowing view and pure on modifiers, but that might make it fairly complex :)

[VoR0220]

Indeed. But he raises a fine point. Modifier isnt exactly the correct keyword for most of these because its not really modifying anything. Moreso prechecking and postoperating on things.

[redsquirrel]

Modifier is the correct keyword in the context of "statement modifiers", which are a common term in Ruby and Perl (maybe other languages too).

[VoR0220]

@redsquirrel good to know! :)

[ethers]

I was aware of contexts like "statement modifiers" which do make sense. Part of this suggestion is to prevent modifiers from being abused: sometimes it may not be clear what should be in a modifier as opposed to a function.

[VoR0220]

should modifiers not be allowed to change state?

[ethers]

should modifiers not be allowed to change state?

Could be another discussion; I was avoiding the discussion for the meantime by suggesting this issue is like an alias just for readonly ones. But it would be good if there were ways that the language could minimize misuse of features: I don't think modifier abuse is an issue currently, but something for us to keep in mind.

[chriseth]

We might add view and pure to modifiers (which is then of course only checked against the modifier's body and not to the function it is applied to), but I'm also fine with adding a precondition keyword. In that case, though, the precondition should be a bool expresison or return a bool and throw if it is false.