```nvec ← {denoms←1 5 6 10 26 39 43} ##.stamps value   ⍝ Postage stamps for ⍵.

Returns a vector of stamps whose total value is the right argument. The optional
left  argument is a vector of distinct stamp values and defaults to those denom-
inations prevalent in the UK circa 1998:

⍺←1 5 6 10 26 39 43         ⍝ Default UK stamp denominations.

Technical note:

Notice  that  the  graph  approach is, in general, better than a simple "greedy"
algorithm, which repeatedly subtracts the largest possible remaining value:

stomps←{                    ⍝ stamps - greedy algorithm.
⍺←1 5 6 10 26 39 43     ⍝ default UK stamp denominations.
svec←⍺                  ⍝ stamp vector.
⍬{                      ⍝ stamp accumulator.
⍵=0:⍺               ⍝ no remaining value: done.
next←⌈/svec×svec≤⍵  ⍝ largest possible stamp.
(⍺,next)∇ ⍵-next    ⍝ next stamp and remainder.
}⍵
}

⍕{disp 2 0∘⍕¨stomps ⍵}¨50 51 52 53          ⍝ less-than-optimal postage.
┌──┬──┬──┐  ┌──┬──┬──┬──┐  ┌──┬──┬──┬──┬──┐  ┌──┬──┐
│43│ 6│ 1│  │43│ 6│ 1│ 1│  │43│ 6│ 1│ 1│ 1│  │43│10│
└──┴──┴──┘  └──┴──┴──┴──┘  └──┴──┴──┴──┴──┘  └──┴──┘

Examples:

⍕{disp 2 0∘⍕¨stamps ⍵}¨ 50 51 52 53         ⍝ default UK(1998) stamps.
┌──┬──┬──┐  ┌──┬──┬──┐  ┌──┬──┐  ┌──┬──┐
│43│ 6│ 1│  │39│ 6│ 6│  │26│26│  │43│10│
└──┴──┴──┘  └──┴──┴──┘  └──┴──┘  └──┴──┘

bins←1 2 4 8 16 32                          ⍝ "binary" stamps:

⍕{disp 2 0∘⍕¨bins stamps ⍵}¨ 15 16 17 18
┌──┬──┬──┬──┐  ┌──┐  ┌──┬──┐  ┌──┬──┐
│ 8│ 4│ 2│ 1│  │16│  │16│ 1│  │16│ 2│
└──┴──┴──┴──┘  └──┘  └──┴──┘  └──┴──┘

⍝ Stamps with a negative face value would be quite handy:

bts←1 ¯1 3 ¯3 9 ¯9 27 ¯27                   ⍝ "balanced ternary" stamps.

⍕{disp 2 0∘⍕¨bts stamps ⍵}¨12 13 14 15      ⍝ see →bt←
┌──┬──┐  ┌──┬──┬──┐  ┌──┬──┬──┬──┐  ┌──┬──┬──┐
│ 9│ 3│  │ 9│ 3│ 1│  │27│¯1│¯3│¯9│  │27│¯3│¯9│
└──┴──┘  └──┴──┴──┘  └──┴──┴──┴──┘  └──┴──┴──┘

⍝ ... although they are unlikely to catch on:
⍝
⍝   "I'd like a 27p stamp please. Oh yeah, and two ¯9s and a ¯3."
⍝   "Thank you sir, that'll be 6p; will there be anything else?"