Toy project for Nabokov's Ada, or Ardor.
For their correspondence in the first period of separation, Van and Ada had invented a code which they kept perfecting during the next fifteen months after Van left Ardis. ... Codes are a bore to describe; yet a few basic details must be, reluctantly, given.
One-letter words remained undisguised. In any longer word each letter was replaced by the one succeeding it in the alphabet at such an ordinal point-- second, third, fourth, and so forth--which corresponded to the number of letters in that word. Thus "love," a four-letter word, became "pszi" ("p" being the fourth letter after "l" in the alphabetic series, "s" the fourth after "o", et cetera), whilst, say, "lovely" (in which the longer stretch made it necessary, in two instances, to resume the alphabet after exhausting it) became "ruBkrE," where the letters overflowing into the new alphabetic series were capitalized: B, for instance, standing for "v" whose substitute had to be the sixth letter ("lovely" consists of six letters) coming after it: wxyzAB, and "y" going still deeper into that next series: zABCDE.
...
In the second period of separation, beginning in 1886, the code was radically altered. Both Van and Ada still knew by heart the seventy-two lines of Marvell's "The Garden" and the forty lines of Rimbaud's "Mémoire." It was from these two texts that they chose the letters of the words they needed. For example, l2.11. l1.2.20. l2.8 meant "love," with "l" and the number following it denoting the line in the Marvell poem, and the next number giving the position of the letter in that line, l2.11, meaning "eleventh letter in second line." I hold this to be pretty clear; and when, for the sake of misleading variety, the Rimbaud poem was used, the letter denoting the line would simply be capitalized.
Vladimir Nabokov, Ada, or Ardor, Part 1, Chapter 26, p160-161.
This program takes as input a text file, encoded in the manner described above, and outputs the translation.
Page numbers are taken from my paperback, which is the February 1990 First Vintage International Edition.