Idea: Simplify syntax with infinite currying

[philer]

This is just an idea, I haven't actually tried it.

Basically the point of the for comprehension is to reduce syntax clutter, i.e. to avoid deeply nested closures etc. However there are still quite a lot of special characters floating around in this example:

For._("dividend", success(42))
   ._("divisor", success(2))
   ._("divisorVerified", ({divisor}) => divisor != 0 ? success(divisor) : failure("Divisor must not be zero!"))
   .yield(({dividend, divisorVerified}) => dividend / divisorVerified)

That ._ doesn't really tell you much, it's just a way of starting a new line. So my idea is to remove the need for ._ on every line and instead turn For into a callable that returns another instance of itself. It could then be used like this:

For
  ("dividend", success(42))
  ("divisor", success(2))
  ("divisorVerified", ({divisor}) => divisor != 0 ? success(divisor) : failure("Divisor must not be zero!"))
  .yield(({dividend, divisorVerified}) => dividend / divisorVerified)

Advantages:

• Less Syntax 💯

Disadvantages:

• Might look even more like black magic.
• I'm not sure if formatters like prettier will deal well with this.

Like I said, it's just an idea, I'd be curious what your thoughts are. :)

[philer]

Another thought I had is that object parameters could be used to combine multiple steps, although I'm not sure if that makes readability better or worse:

For({
  dividend: success(42),
  divisor: success(2),
  divisorVerified: ({divisor}) => divisor != 0 ? success(divisor) : failure("Divisor must not be zero!"),
}).yield(({dividend, divisorVerified}) => dividend / divisorVerified)

In this case the implementation would rely on (1) each step having a unique name and (2) JS iterating object keys in insertion order (which is guaranteed since ES5 iirc).

[p3et]

Thanks for your feedback @philer! I totally agree that both versions look nicer than the current one. However, can they be implemented in a type-safe way? For example, it must be guaranteed that every arrow function parameter has the same type as the inner monad value at definition. For example, ({divisor}) => ... must be a number.