tomstuart

>> IF = -> b { b }
=> #<Proc:0x007fb4e4049cc8 (lambda)>

>> LEFT = -> p { p[-> x { -> y { x } } ] }
=> #<Proc:0x007fb4e403d680 (lambda)>

>> RIGHT = -> p { p[-> x { -> y { y } } ] }
=> #<Proc:0x007fb4e4028ff0 (lambda)>

>> IS_EMPTY = LEFT