Constraints on definition of `length` should be strengthened

[Henning Thielemann]

On Mon, 3 Apr 2017, Sven Panne wrote:

> Of course such an interpretation is possible, but let's remember Abelson's famous quote:
> 
>    "Programs must be written for people to read, and only incidentally for machines to execute."
> 
> When you show somebody a pair and ask "What is this?", how many people 
> do you *seriously* expect to say "Oh, yeah, I've seen that: It's a value 
> on the right decorated by another one on the left!" compared to people 
> telling you something about e.g. cartesian products (which are totally 
> symmetric with no bias to the right or left)? The point is: Using a pair 
> for a decorated one-element container is completely miscommunicating 
> your intent, even if you find a sensible mathematical interpretation for 
> it.

That's what I am saying all the time.