I'm trying to do some currying in ruby:
def add(a,b) return a+b end plus = lambda {add} curry_plus = plus.curry plus_two = curry_plus[2] #Line 24 puts plus_two[3] I get the error
func_test.rb:24:in `[]': wrong number of arguments (1 for 0) (ArgumentError) from func_test.rb:24:in `'
But if I do
plus = lambda {|a,b| a+ b} It seems to work. But by printing plus after the assigning with lambda both ways return the same type of object. What have I misunderstood?
You're on the right track:
add = ->(a, b) { a + b } plus_two = add.curry[2] plus_two[4] #> 6 plus_two[5] #> 7 As others have pointed out, the plus lambda you defined doesn't take any arguments and calls the add method with no arguments.
lambda {|a,b| a+ b} Creates a lambda which takes two arguments and returns the result of calling + on the first, with the second as its arguments.
lambda {add} Creates a lambda which takes no arguments and calls add without arguments, which is an error of course.
To do what you want, you should do
plus = lambda {|x,y| add(x,y)} or
plus = method(:add).to_proc 
:add.to_proc will not work right. It returns a Proc equivalent to proc {|receiver, *args| receiver.add(*args)}. Which means that :add.to_proc[1,2] will try to call 1.add(2) rather than self.add(1,2).When you write lambda {add}, you're declaring a Proc that takes no arguments and, as its sole action, calls add with no arguments. It doesn't turn add into a Proc. On the other hand, lambda {|a,b| a + b} returns a Proc that takes two arguments and adds them together — since it takes arguments, it's valid to pass arguments to that one.
I think what you want is method(:add).to_proc.curry.
