change Monoid#empty from nullary function to identity element itself

[michaelficarra]

😅

[puffnfresh]

😐

[5outh]

I think I'm in favor of this, does it screw with anything? @puffnfresh

[puffnfresh]

No preference. Can construct an argument either way.

[SimonRichardson]

Question: should changes like this PR also fix all the other fantasy-land repos? By that I mean, if you create a PR like this, I'm expecting PRs for all the repos in fantasy-land which this breaks?

[5outh]

On second thought, changing the spec from how it was may cause other peoples' projects to no longer conform to it. If there's no preference either way, I think we should keep it the way it is.

[joneshf]

We're semver'ing this thing, so we could just bump the version.

[5outh]

I think @SimonRichardson has a point, we should keep all of the fantasy-repositories up to date with the latest version, which is kind of unfortunate.

Should we take this to a vote or something?

[davidchambers]

This approach is incompatible with the current Id implementation:

// Monoid (value must also be a Monoid)
Id.prototype.empty = function() {
    return new Id(this.value.empty ? this.value.empty() : this.value.constructor.empty());
};

[SimonRichardson]

Can we close this, it doesn't seem to over any value and consider it could break implementations I don't see the point. I hope you don't mind?