I agree that "purity" is rather hard to ensure and probably not needed, more
like a safeguard against bad code.
I think main benefit is semantics: in Elixir it is single block and only 3
(presumably) operations are allowed:
* New variable iteration (Cartesian product style)
* Variable assignment
* Condition (if `false` then stop and begin new iteration)
When there are more allowed operations it also complicates the reading in the
sense that one cannot read top-to-bottom because we should also account for
mid-level else-branches, mutating variables (something with `var`). And when
this complexity is present it really stops being "list comprehension" and more
like a shortcut for several symbols:
rs = @[] # replace with `collect(newSeq)`
for ...
...
rs.add n # yay we can omit `rs.add`
Run
I understand that distinction is subtle but I would agree that "cleaner" style
of more restrictive set of operations and single indentation level lead to
better code. I also understand that in Python and Elixir list comprehension is
implemented as a language construct compared to our user-space macro and hence
the trade-offs can be reasonable.
