of all the gifts with the repetitions listed in the song. The people mentioned in the song are hired, not purchased. The total costs of all goods and services for the 2015 Christmas Price Index is US$34,130.99, or $155,407.18 for all 364 items. The original 1984 cost was $12,623.10. The index has been humorously criticised for not accurately reflecting the true cost of the gifts featured in the Christmas carol. John Julius Norwich's 1998 book, The Twelve Days of Christmas (Correspondence), uses the motif of repeating the previous gifts on each subsequent day, to humorous effect. Computational complexity In the famous article The Complexity of Songs, Donald Knuth computes the space complexity of the song as function of the number of days, observing that a hypothetical "The Days of Christmas" requires a memory space of as where is the length of the song, showing that songs with complexity lower than indeed exist. Incidentally, it is also observed that the total number of gifts after days equals . In 1988, a C program authored by Ian Phililipps won the International Obfuscated C Code Contest. The code, which according to the jury of the contest "looked like what you would get by pounding on the keys of an old typewriter at random", takes advantage of the recursive structure of the song to print its lyrics with code that is shorter than the lyrics themselves. Notes References Footnotes Bibliography Opie, Peter and Iona, eds. The Oxford Dictionary of Nursery Rhymes. Oxford: Oxford University Press, 1951, pp. 122–230, . External links Free online simple melody score for all verses (as JPEGs or a PDF file) in English and Esperanto: "The Twelve Days of Christmas / La Dek Du Tagoj de Kristnasko" British Christmas songs Christmas carols Cumulative songs Christmas in England 12 (number)