Question

I’m trying to learn Ruby right now after learning Python and I’m having trouble translating this code to Ruby:

def compose1(f, g):
    """Return a function h, such that h(x) = f(g(x))."""
    def h(x):
        return f(g(x))
return h

Do I have to translate this using blocks? Or is there a similar syntax in Ruby?

Answer 1

Lets say f and g are the following methods:

def f(x)
  x + 2
end

def g(x)
  x + 3
end 

We can define compose1 as:

def compose1(f,g)
  lambda { |x| send(f, send(g, x) ) }
end

For this to work, we need to define h as:

h = compose1(:f, :g)

You will need to pass the method names as a string / symbol for send to work. Then, you can do

h.call 3 # => 8. More info can be found here