Add concat to Maybe, Either and Identity

[evilsoft]

Lets just start with these

This PR was requested by an early tester of things. It adds concat to the simple value types and will concat inner values if they contain Semigroups of the same type.

Also there is a BIG ol breaking change: I updated isSameType to be able to compare native JS types, not just the crocks types. So things like this can be done:

• isSameType(String, 'hello') // true
• isSameType('goodbye', 'hello') // true
• isSameType('goodbye', Array) // false
• isSameType([ 'a' ], 'a') // false

[coveralls]

Coverage remained the same at 100.0% when pulling 9c118e3 on semigroup-all into 6263d10 on master.

[coveralls]

Coverage remained the same at 100.0% when pulling 9c118e3 on semigroup-all into 6263d10 on master.

[rstegg]

found possible fix, let me know what you think

[rstegg]

M(String).concat(M(Number)) or M(Array).concat(M(Number)) should work, so should it include: !isSameType(left, left.concat(right)) somehow?

[evilsoft]

If I think I understand what you are saying, I think you are saying that this would not throw an Error:

const m = Maybe.of('hello')
const n = Maybe.of(3)

// will fail as Number is NOT a semigroup
m.concat(n)

if you look we are mapping on m, which is the container passed into us. So right will be a Number and it is not the same type as String, so this fails.

Now if you are saying that they are passing in the actual constructors Array and String
That would fail because Array is not a semigroup.

Is that what you mean?

[evilsoft]

What would this possible fix actually fix.
Do you have a working example that shows what you found that is broken?
It is hard to pin down what you found to be broken with that description.

[evilsoft]

Or are you saying that it should not error?

[evilsoft]

From gitter chat, it seems that you meant that I should be able to [ 'a' ].concat('b'). While that is true in JS, for these types of interaction I am going to go with the FL spec for semigroup.

So I do not see an error here.

[rstegg]

nope i am wrong; i meant fix to a possible error, bad wording.

[evilsoft]

Seems legit. Merging!