Split an iterable into fixed-size Groovy batches

List<List> chunk(Iterable source, int size) {
    if (size < 1) throw new IllegalArgumentException('size must be >= 1')
    List<List> batches = []
    List current = []
    for (item in source) {
        current << item
        if (current.size() == size) {
            batches << current
            current = []
        }
    }
    if (current) batches << current
    batches
}

println chunk(1..7, 3)