tuples.rb

# The point is that only functions and function application are required to create all
# higher level language abstractions.  You can use church encoding to turn functions
# into numbers, boolean values, logical operators, math operators, and in this case
# data structures.

fst = -> (a,_) { a }    # no matter what 2 values are passed in return the 1st
snd = -> (_,b) { b }    # no matter what 2 values are passed in return the snd

# a tuple is a function, that takes a function as an argument and applies it to the constant values of the tuple
tuple1 = ->(f){ f.('alpha', 'omega') }
tuple2 = ->(f){ f.('apple', 'orange') }

# to get a value out of a tuple you pass the function 'fst' or 'snd' to it.
puts tuple1.(fst)     # -> alpha
puts tuple2.(snd)     # -> orange

# you don't have to squint very hard to see the similarity typical oop code, tuple.fst or tuple.snd

# You can make a tuple constructor to simplify creating tuples
cons = -> (a,b) { ->(f){ f.(a, b) } }

# to use the constructor just pass it 2 values
tuple3 = cons.('fire', 'water')

# Just like before you use `fst` or `snd` to get values out.
puts tuple3.(fst)
puts tuple3.(snd)