Re: [Chicken-users] Expanding ellipsis on lists of different length

[Tobia Conforto]

felix winkelmann wrote:
> alexpander accepts this form, but gives an error if the lists are of  
> unequal length.

I believe this is the correct behaviour.  Chicken gives an error only  
when the first list is longer than the second, not when it's shorter.


Elf wrote:
> the untest case is always valid, the test case is only valid when  
> input is of the same length.

Yes, that's my point.

> i am confused.  are you proposing that it should always signal an  
> error when getting the split ellipses like this, or when the lists  
> are mismatched? (the second case is a bit unpleasant to try to catch  
> all the time, and would probably have performance unplesantnesses.)


It should signal an error when they are mismatched.

I believe it's only a matter of using a version of map that checks  
this condition: that all its arguments become '() at the same time.   
Maybe it would be useful to modify map itself in this way?

;; correct, this is an error
(map list '(1 2 3) '(10 20))
=> Error: (map) lists are not of same length: (())

;; not so correct, this should be an error too
(map list '(1 2) '(10 20 30))
=> ((1 10) (2 20))


Tobia