Tech Edit: Chapter 7

[DrBoolean]

There is some brilliant stuff in this chapter. I really like the church encodings in stuff like trackEvent which gives an intuition for how the state monad works.

The summary is so damn good. Just some corrections on the isomorphic stuff:

• The next time you hear someone say "X is isomorphic with Y", what they mean is, "X and Y can be converted from either one to the other in either direction, and maintain the same behavior regardless.

But "maintain the same behavior" is a little off - usually that's precisely the point e.g. Array<Char> is isomorphic to String, but they have different behavior. I'd say "maintain the same information".

Also, we usually we say "X is isomorphic /to/ Y" :)

• "they are isomorphisms of each other" => "they are isomorphic to each other"

• minor typo more similar than dislike

That's all it got! Great chapter.

[getify]

Would it be more accurate to say "maintain the same capability" or "maintain the same outcome"?

[DrBoolean]

Well, I think the main use case of an isomorphism in FP is to make a type conversion to get new behavior, then convert it back after. So like a linked list can turn into an array to gain some operation, then back afterward. Or a multi-dimensional array can turn into a rose tree and back. Things like that.

So "holds same information" captures the use a little better than "has same capability" even though that makes sense as well.