Here are two methods defined in the Proc class, designed to be used
for functional programming:
def apply(enum)
enum.map &self
end
alias | apply
def reduce(enum)
enum.inject &self
end
alias <= reduce
Here's an application of them:
sum = lambda {|x,y| x+y }
mean = (sum<=a)/a.size
deviation = lambda {|x| x-mean }
square = lambda {|x| x*x }
standardDeviation = Math.sqrt((sum<=square|(deviation|a))/(a.size-1))
This excerpt is taken from "The Ruby Programming Language".
Here's the thing. In the last line of the above code it uses
"sum<=square". That reduce method expects an enumerable as an
argument. And instead it is being sent a lambda held in square
variable. This should fail because the inject method does not exist on
the lambda. It exists on arrays, and other enumerable types. So what
am I missing here?
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