From: Joel VanderWerf <joelvanderwerf@...>
Date: 2010-09-07T02:58:03+09:00
Subject: Re: Odd functional programming question

On 09/06/2010 06:40 AM, Peter Hickman wrote:
> Ok this is probably not really functional programming but I was just
> noodling about with Ruby when I thought "it would be quite nice if I
> could do X". In this case X is as follows:
>
> def X(text, action)
>    x.action
> end
>
>>> X("abcedf", size)
> =>  6
>>> X("abcdef", upcase)
> =>  "ABCDEF"
>>> X("abcdef", gsub(/[aeiouy]/, '_'))
> =>  "_bcd_f"
>
> Quite clearly this does not actually work, otherwise I wouldn't be
> asking. But is there some way in Ruby to do something like this?
>

Looks like a case for #instance_exec.

def foo(x, &action)
   x.instance_exec(&action)
end

p foo("abcedf") {size}
p foo("abcdef") {upcase}
p foo("abcdef") {gsub(/[aeiouy]/, '_')}

# unlike #send, you can have more complex code than one single
# method call
p foo("abcdef") {self+reverse}

# also #instance_exec lets you pass thru args, which gives you
# some flexibility in how you factor actions
def bar(x, *args, &action)
   x.instance_exec(*args, &action)
end

p bar("abcdef", /[aeiouy]/, '_') {|pat, str| gsub(pat, str)}