attempt to call method 'double' (a nil value)

[akarshinfrrd]

When I try to run similarity-db.lua in the 9-similarity-db folder, I get the below error:

luajit: similarity-db.lua:39: attempt to call method 'double' (a nil value)
stack traceback:
similarity-db.lua:39: in function 'similarityDb'
similarity-db.lua:75: in main chunk
[C]: at 0x00405d50

As far as what I looked up, "a nil value" means that the function does not exist. The closest article on that I came across was this karpathy/char-rnn#2, but the issue was resolved by re-building Torch. I have done that several times. I have build it using LUAJIT and Lua as described in http://torch.ch/docs/getting-started.html

Please let me know if I am missing something here. Thanks in advance!