Loops, Folds and Tuples

For-loops Given an initial state defined by a number of variables, a for-loop iterates through its argument array modifying the state.     A←… ⋄ B←… ⋄ C←…       ⍝ initial state     :For item :In items         ⍝ iterating through array “items”         A←A … item            ⍝ new value for A depending on item         C←C … A … item      ⍝ new value for C depending on A and item         …                     ⍝ state updated     :EndFor     A B C                       ⍝ […]