```//given a list of entries, we need to return Ei...

# arrow

[Fred Friis]

//given a list of entries, we need to return Either<Error, Boolean> where the boolean is true only if
//there were no errors calling the downstream for all entries AND only if the response from the downstream
//was true for all entries

kotlin
return entries
    .map { callDownstreamForEntry(it) } //now we have a List<Either<IError, Boolean>
    .sequence(Either.applicative()) //turn it into Either<FirstError, List<Boolean>>

    .fix() //please the compiler, won't be necessary in newer versions of Arrow
    .map { it.fix() } //please the compiler, won't be necessary in newer versions of Arrow

     //now map on the Either<FirstError, List<Boolean>>
    .map { listOfBooleans ->
        listOfBooleans
            .fold(
                true, //start with true
                { sofar, currentItem ->
                    sofar && currentItem
                    //this will turn the list of booleans into a single boolean true if all
                    //booleans in the list are true, or a single boolean false if there is a
                    //single boolean false in the list
                })
    }

//the above code does that
//BUT
//if we get an error OR a right<false> from the downstream, rather than continuing to map through all
//entries (the list can be very large) we would like to fail fast
//this is easy to do with a for loop but if possible it would be nice to do it functionally