Local accumulators for cleaner comprehensions

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A compromise would be a block:

accum session_counter <- 0, lesson_counter <- 0 do
  ...
end

It has benefits from both approaches:

  1. The block helps limit the scope of where the variables are used, so we worry less about large functions
  2. No additional syntax noise such as @@ (although that can be a cons as usage is less clear)

It also helps keep the theme that all of for, with, and then accum are actually monads (but let’s not call them that :sweat_smile:).

Of course, the other option is to introduce the accumulators directly into comprehensions, as others suggestions:

list = [1, 2]
for val <- list, binding: [a: 0, b: 1] do
  a = a + val
  b = b + val
end

But the comprehension syntax is already quite overloaded, unfortunately, and different enough to add to the confusion (imo)

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