list/set comprehension

[danilopedraza]

I want to use list and set comprehensions, just like in Python, SETL and Picat (which I found recently). That will require the addition of a keyword like for, in, or both.

[danilopedraza]

I will define two tipes of set comprehensions:

• property sets: a set that, in general, cannot be generated or iterated through, and its only purpose is to verify properties. Something like

let ZPlus := { k : k >= 1 }
2 in ZPlus # true

• tangible sets: a property-based restriction of a structure that can be generated or iterated through. Something like

let nums := [1, 2, 3, 4, 5, 6]
for even in { k in nums : isEven(k) }:
    println(even)

[danilopedraza]

Following this definitions, every tangible set is a property set, but the inverse is not true.

[danilopedraza]

I think of list comprehensions the same way Picat does: is just an idiomatic way of mapping an iterable. They are always like this:

[ f(k) : k in iterable ]

While sets can be seen as properties, lists are always seen as ordered containers, independently of how they are generated (lazily or not).

[danilopedraza]

This is naively implemented right now.