here explicitly variables are introduced
=> these range over a sequence of values
# return all cities in which conferences happen for $city in // city for $conf in // conferences where happens ( event: $conf, location: $city, ... ) return ( $city )
is down-translated into:
[[ [ happens ( ... $conf ... $city ... ) ] ]] ( $city ) | $conf => [[ // conferences ]] | $city => [[ // city ]] # eliminating variable $conf = [[ // conferences ]] . [[ [ happens ( ... $0 ... $city ... ) ] ]] ( $city ) | $city => [[ // city ]] # eliminating variable $city = [[ // city ]] . ( $0, [[ // conferences ]] ) . [[ [ happens ( ... $1 ... $0 ... ) ] ]] ( $0 ) # look ma: no variables!