lambda二回呼び出し。
javascript
js> (function(x){return function(y){return x+y}})(1)(2) 3
ruby
irb(main):001:0> Proc.new{|x|Proc.new{|y|x+y}}.call(1).call(2) => 3
js> (function(x){return function(y){return x+y}})(1)(2) 3
irb(main):001:0> Proc.new{|x|Proc.new{|y|x+y}}.call(1).call(2) => 3