Issue #9783 has been updated by Arne Brasseur.

File 0001-Implement-Method-curry-which-delegates-to-to_proc.cu.patch added

Updated the patch with documentation. There's an interesting side effect to be considered. `Method#to_proc` returns a lambda that checks its arity. `Proc#curry` takes an optional `arity` argument. If this doesn't match the method's arity then the result can not be called.

~~~

def two_args(a,b)
end

curried = method(:two_args).to_proc.curry(1)

curried.(1)
#  -:4:in `curry': wrong number of arguments (1 for 2) (ArgumentError)
#  	from -:4:in `<main>'

curried.(1, 2)
#  -:4:in `curry': wrong number of arguments (1 for 2) (ArgumentError)
#  	from -:4:in `<main>'

curried.(1, 2, 3)
#  -:4:in `curry': wrong number of arguments (1 for 2) (ArgumentError)
#  	from -:4:in `<main>'

~~~

In the case of a method with variable arguments the arity argument is important though, because otherwise the currying has no effect.

~~~
def varargs(*args)
  args
end

curried = method(:varargs).to_proc.curry
curried.(1) # => [1]
curried.(1,2) # => [1, 2]
curried = method(:varargs).to_proc.curry(3)
curried.(1) # => #<Proc:0x007f0cb8fc6fe0 (lambda)>
curried.(1).(2).(3) # => [1, 2, 3]
~~~

I think it would make sense for a `Method#curry` method to raise an error or at least give a warning when passing the wrong arity to a fixed-arity function.

----------------------------------------
Feature #9783: [PATCH] Add Method#curry
https://bugs.ruby-lang.org/issues/9783#change-46364

* Author: Arne Brasseur
* Status: Open
* Priority: Normal
* Assignee: 
* Category: core
* Target version: 
----------------------------------------
There is already Proc#curry, but to curry a method you need to go through to_proc. This patch adds `Method#curry` which delegates to `method.to_proc.curry`.

Looking forward to seeing this discussed.

---Files--------------------------------
0001-Implement-Method-curry-which-delegates-to-to_proc.cu.patch (1.86 KB)
0001-Implement-Method-curry-which-delegates-to-to_proc.cu.patch (3.19 KB)


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