From: "Ara.T.Howard" <Ara.T.Howard@...>
Date: 2005-05-23T00:13:01+09:00
Subject: Re: join not in Enumerable

On Sun, 22 May 2005 nobu.nokada@softhome.net wrote:

> Hi,
>
> At Sun, 22 May 2005 08:56:08 +0900,
> Ara.T.Howard wrote in [ruby-talk:143311]:
>> the only reason i can think of is that just because somthing is countable
>> (Enumerable) doesn't mean each sub-thing is singular.  take a hash for
>> example.  this is no stubling block (pun intended) for ruby however:
>
> Feels interesting.
>
>
> Index: enum.c
> ===================================================================
> RCS file: /cvs/ruby/src/ruby/enum.c,v
> retrieving revision 1.54
> diff -U2 -p -r1.54 enum.c
> --- enum.c	30 Oct 2004 06:56:17 -0000	1.54
> +++ enum.c	22 May 2005 09:36:21 -0000
> @@ -967,4 +967,52 @@ enum_zip(argc, argv, obj)
> }
>
> +static VALUE
> +enum_join_s(obj, arg, recur)
> +    VALUE obj, *arg;
> +    int recur;
> +{
> +    if (recur) {
> +	static const char recursed[] = "[...]";
> +	if (!NIL_P(arg[1]) && RSTRING(arg[0])->len != 0) {
> +	    rb_str_append(arg[0], arg[1]);
> +	}
> +	rb_str_cat(arg[0], recursed, sizeof(recursed) - 1);
> +    }
> +    else {
> +	if (rb_block_given_p()) {
> +	    obj = rb_yield(obj);
> +	}
> +	if (TYPE(obj) != T_STRING) {
> +	    obj = rb_obj_as_string(obj);
> +	}
> +	if (!NIL_P(arg[1]) && RSTRING(arg[0])->len != 0) {
> +	    rb_str_append(arg[0], arg[1]);
> +	}
> +	rb_str_append(arg[0], obj);
> +    }
> +    return arg[0];
> +}
> +
> +static VALUE
> +enum_join_i(el, arg)
> +    VALUE el, arg;
> +{
> +    return rb_exec_recursive(enum_join_s, el, arg);
> +}
> +
> +static VALUE
> +enum_join(argc, argv, obj)
> +    int argc;
> +    VALUE *argv;
> +    VALUE obj;
> +{
> +    VALUE arg[2];
> +
> +    rb_scan_args(argc, argv, "01", &arg[1]);
> +    arg[0] = rb_str_new(0, 0);
> +    rb_iterate(rb_each, obj, enum_join_i, (VALUE)arg);
> +    return arg[0];
> +}
> +
> /*
>  *  The <code>Enumerable</code> mixin provides collection classes with
> @@ -998,4 +1046,5 @@ Init_Enumerable()
>     rb_define_method(rb_mEnumerable,"inject", enum_inject, -1);
>     rb_define_method(rb_mEnumerable,"partition", enum_partition, 0);
> +    rb_define_method(rb_mEnumerable,"classify", enum_classify, 0);
>     rb_define_method(rb_mEnumerable,"all?", enum_all, 0);
>     rb_define_method(rb_mEnumerable,"any?", enum_any, 0);
> @@ -1008,4 +1057,5 @@ Init_Enumerable()
>     rb_define_method(rb_mEnumerable,"each_with_index", enum_each_with_index, 0);
>     rb_define_method(rb_mEnumerable, "zip", enum_zip, -1);
> +    rb_define_method(rb_mEnumerable, "join", enum_join, -1);
>
>     id_eqq  = rb_intern("===");

only you would crank that out in C nobu ;-)


looks good for enumerable:

   harp:~/build/ruby > ./ruby -e' p( {:k => :v, :K => :V }.join(","){|kv| kv.join "=>"} )  '
   "k=>v,K=>V"

but doesn't override Array's current behaviour:

   harp:~/build/ruby > ./ruby -e'a3 = [  [ [4], [2] ],  [ ["forty"], ["two"] ]  ]; p a3.join("___"){|a2| a2.join("__"){|a1| a1.join "_"}}'
   "4___2___forty___two"


i'm not sure how to do this in C:

   module Enumerable
     def join(sep = '', &b)
       inject(nil){|s,x| "#{ s }#{ s && sep }#{ b ? b[ x ] : x }"}
     end
   end
   class Array
     def join(*a, &b); super; end
   end

so Array's join is clobbered...

kind regards.


-a
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