putState?

Is there a built-in parser, analogous to putState (formerly, setState) in Parsec that sets the user state and returns nothing? Is there a mechanism to replace user state without performing an explicit mutation/side effect (e.g., userState.tags.push(...) like in the examples in the readme)?

[GregRos]

@mgreenbe Interesting! I never really thought about reverting user state. And yeah, you’re right, it’s probably not possible unless I allow replacing user state in the first place.

Now that I see the reasoning, it’s definitely something I’ll add. The two techniques can be complementary.

[mgreenbe]

My reasoning is twofold: A putState parser would make it really simple to port things from (F)Parsec. Second, I’d like userState state to revert if the parser needs to backtrack, and that won’t happen automatically if I’m always mutating it in place (right?).