What if someone discovered that the specifications in a font file could be Turing complete? What if that person realized that a font could, therefore, perform computations. How about addition?
Proving the Turing Completeness of Fonts:
The goal is:
I wanted to try to implement addition. The input glyph stream would be of the form "=1234+5678=" and the shaping process would turn that string into "6912".
The sheer number of details precludes a simple summary. Mix a little recursion with a strong helping of remapping to implement some grammar productions and voila! The font file is available on Google drive.
What "creative" [mis]applications of this technology can you think of? Define a font file that has a 1:1 mapping of all ASCII characters... except replace all instances of "123" with "456". How could you recognize this had happened to you?
Consider: embedding it in a web page or a PDF document. Making it a new (default) printer font.
(Score: 2) by DrkShadow on Thursday March 14 2019, @11:47AM (1 child)
Xerox was altering input numbers _years_ ago!
http://www.dkriesel.com/en/blog/2013/0802_xerox-workcentres_are_switching_written_numbers_when_scanning [dkriesel.com]
When you'd scan the document, Xerox would run OCR across the document (for storage efficiency?), and you'd get incorrect numbers. This would happen with an operation as simple as copying.
(Score: 2) by maxwell demon on Thursday March 14 2019, @12:30PM
But was the Xerox copying process Turing complete?
The Tao of math: The numbers you can count are not the real numbers.