Reduce is a function or method that is used to take the values in an array or a list and apply a function to successive members of the list to produce (or reduce them to), a single value.



Task

Show how reduce (or foldl or foldr etc), work (or would be implemented) in your language.



See also

 Wikipedia article:   Fold
 Wikipedia article:   Catamorphism


proc fold {lambda zero list} {
    set accumulator $zero
    foreach item $list {
	set accumulator [apply $lambda $accumulator $item]
    }
    return $accumulator
}