THE TRANSPORT move a value from one cell to another — the palindrome breaks
To transport a cell is to relocate its value to a different position. Move the core 4 out to the rim (position 0) and the tape becomes [4,1,2,3,4,4,3,2,1,0] — and now it is no longer a palindrome: the ends no longer match. Transport is a permutation of the cells, and a permutation can break the balance that made the nesting well-formed. Its mirror is dart 336, the restore: because the write was non-destructive (dart 328), the original tape still exists — so restoring the transported value to its home is always possible, and the balance returns. Move out, move back; break the palindrome, then heal it.
THE TECHNIQUE relocate a[src]→a[dst]; a permutation that can break balance
The demo transports the core value to the outer shell — watch the palindrome break: live demo
HISTORY & CREDIT relocation / permutation of cells
“Moving a value is harmless.” — a transport is a permutation, and a permutation can break a structure's balance: the matched nesting becomes unmatched. Movement has consequences for form. cited
relocation · the move / permutation of cell contents — the primitive under sorting, shuffling, and memory copies. form-breaking · a permutation need not preserve a structural invariant; here it breaks the palindrome. mirror · dart 336, the restore: value semantics keep the original, so the move is always undoable.
The 4 lands at the rim and the ends stop matching; the form is broken by the move. To transport is to risk the balance — and to trust the restore. the move
RECOMMEND FOR I-13 the relocation, on the compiler
On the canonical compiler, transporting the core value to position 0 puts 4 at the rim — and the tape is no longer matched:
$ i13 run d_transport.i13 # a[0] <- a[4]
RUN OK · 30 step(s) · peak stack 11 · call depth 1
moved = 4 -- the core value, now at the outer shell (palindrome broken)
Recommend: the transport is relocation — a permutation of cells — and its point in the batch is that moving a value can break the form: after it, the tape's ends no longer match, and the bridge (dart 340) would report 0. Not a keeper (a permutation is not a structural guarantee, and reversibility here is the self-inverse axis). Its meaning is the pair with dart 336, the restore: the value leaves home and, because nothing was destroyed, comes back.