Learning Torch7. Part 1

(part 1, aka: "The First Circle")

My entry point is this:
https://github.com/torch/torch7/wiki/Cheatsheet#newbies

I've read this page cover-to-cover and obtained a machine on which torch was installed. Installing it sounds like a nightmare and I wonder if the performance over a docker container would be the same, making the installation seem like a bad dream. So - read is step 1, installation is step 2.

Step 3 is according to the Newbies training course is to Learn Lua in 15 Minutes:
http://tylerneylon.com/a/learn-lua/

Notable comments:

• nil is the local None/null/void/undefined.
• do/end wrap blocks (just like { and } would in other languages)
• There is no ++, += operators, so  n = n+1  is the way to go.
• == , ~= for equal/nonequal test.
• .. is string communication
• Anything undefined evaluates to nil. (So you can type 'lkgjadsgjdas' into the interpreter without getting an error).
• Only nil and false are considered false. 0 is true!

How to create tables:

-- Literal notation for any (non-nil) value as key: t = {key1 = 'value1', key2 = false}
u = {['@!#'] = 'qbert', [{}] = 1729, [6.28] = 'tau'} print(u[6.28]) -- prints "tau"
Matching keys within tables: -- Key matching is basically by value for numbers -- and strings, but by identity for tables. a = u['@!#'] -- Now a = 'qbert'. b = u[{}] -- We might expect 1729, but it's nil: -- b = nil since the lookup fails. It fails -- because the key we used is not the same object -- as the one used to store the original value. So -- strings & numbers are more portable keys.

Python dir() equivalent

print(_G) ~~ dir()

Using tables as lists/arrays:

-- List literals implicitly set up int keys:

v = {'value1', 'value2', 1.21, 'gigawatts'} for i = 1, #v do -- #v is the size of v for lists. print(v[i]) -- Indices start at 1 !! SO CRAZY! end -- A 'list' is not a real type. v is just a table -- with consecutive integer keys, treated as a list.

The other meaningful parts, to be read thoroughly in the tutorial, are the metatables parts.