From: Gavin Sinclair <gsinclair@...>
Date: 2004-05-24T12:21:41+09:00
Subject: Re: an idea regarding map

SegPhault wrote:
>
> just some syntactic nitpicking:
>
> If I want to perform a map operation using a function...
>
> def somefunc(x)
>   # ... perform some operation on x ...
>   # ... and return a value ...
> end
>
>  I have to do this:
>
> l = [1,2,3].map { |x| somefunc x }
>
>  Why shouldn't I be able to do this:
>
> l = [1,2,3].map somefunc

It's just not how Ruby works, for a number of reasons.  If 'somefunc' were
truly a function, then it would seem strange not to be able to do that. 
But 'somefunc' is a method, and as such it is bound up in the state of
some object.

Ruby will not sacrifice the purity of its OO concept for a bit of extra
convenience.  (It already has convenience in spades.)

The 'extensions' project on RubyForge has a couple of shortcuts aimed at
map, but not in the (function-oriented) way you want.

  require 'extensions'

  a = [1, -2, 3]
  a.mapf :abs     # short for a.map { |n| n.abs }
  a.map &:abs     # ditto

The second example is a bit ugly and opaque, but it can be applied to any
method, whereas the first is obviously limited to map/collect.

An alternative for your code is

  a.map method(:somefunc)

Ultimately, you have to look at your suggested code

  a.map somefunc

and realise that 'somefunc' must be either a local variable or a method
invocation.  Treating it as a method object (like method(:somefunc)) would
mean that all method invocations would require parentheses, which would be
unpopular.

Cheers,
Gavin