------ art_37612_15120926.1225471974095 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Content-Disposition: inline On Fri, Oct 31, 2008 at 10:08 AM, David A. Black <dblack / rubypal.com> wrote: > On Sat, 1 Nov 2008, Jacob Fugal wrote: > > Thinking about it more, I realize that would make the ary.inject(:foo) >> usage >> inconsistent, as :foo would be interpreted as "initial" rather than >> "block". >> The error is basically saying: "You didn't provide a block, so I was going >> to try using the first argument as a proc, but it wasn't a proc, nor was >> it >> a Symbol that I could convert into a proc." -- so it *was* complaining >> about >> a missing block parameter, but only implicitly. >> >> Perhaps rather than checking for a Symbol explicitly, just check for >> #responds_to?(:to_proc)? If it does, call it and use the result as the >> block. If not, the error message could say something like "TypeError: 0 >> cannot be converted to a Proc". >> > > I thought that the idiom was (&:sym), not just (:sym). I certainly > would expect a non-& argument to inject to be the initial value for > the accumulator and not magically converted to something else. If > there's no block I think I would expect this: > > obj.inject(other_object) > > to mean this: > > obj.enum_for(:inject, other_object) > > Special-casing symbols like that seems much too magic and restrictive > to me. I agree wholeheartedly. I was not previously aware of a obj.inject(:sym) usage, but that's the only sense I could make of the error. My original off-the-cuff hypothesis that the error stemmed from inside Symbol#to_proc makes absolutely no sense on second inspection, so it must be the inject method that's checking for a symbol. Sure enough, the rdoc at http://redmine.ruby-lang.org/repositories/entry/ruby-19/enum.c#L449indicates such special treatment for Symbols as the sole argument and the error raised stems from the call to rb_to_id that occurs at line 507. Jacob Fugal ------ art_37612_15120926.1225471974095 Content-Type: text/html; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Content-Disposition: inline On Fri, Oct 31, 2008 at 10:08 AM, David A. Black <span dir tr"><<a href ailto:dblack / rubypal.com">dblack / rubypal.com</a>></span> wrote:<br><div class mail_quote"><blockquote class mail_quote" style order-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;"> <div><div class j3C7c">On Sat, 1 Nov 2008, Jacob Fugal wrote:<br> <br> <blockquote class mail_quote" style order-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;"> Thinking about it more, I realize that would make the ary.inject(:foo) usage<br> inconsistent, as :foo would be interpreted as "initial" rather than "block".<br> The error is basically saying: "You didn't provide a block, so I was going<br> to try using the first argument as a proc, but it wasn't a proc, nor was it<br> a Symbol that I could convert into a proc." -- so it *was* complaining about<br> a missing block parameter, but only implicitly.<br> <br> Perhaps rather than checking for a Symbol explicitly, just check for<br> #responds_to?(:to_proc)? If it does, call it and use the result as the<br> block. If not, the error message could say something like "TypeError: 0<br> cannot be converted to a Proc".<br> </blockquote> <br></div></div> I thought that the idiom was (&:sym), not just (:sym). I certainly<br> would expect a non-& argument to inject to be the initial value for<br> the accumulator and not magically converted to something else. If<br> there's no block I think I would expect this:<br> <br> obj.inject(other_object)<br> <br> to mean this:<br> <br> obj.enum_for(:inject, other_object)<br> <br> Special-casing symbols like that seems much too magic and restrictive<br> to me.</blockquote></div><br>I agree wholeheartedly.<br><br>I was not previously aware of a obj.inject(:sym) usage, but that's the only sense I could make of the error. My original off-the-cuff hypothesis that the error stemmed from inside Symbol#to_proc makes absolutely no sense on second inspection, so it must be the inject method that's checking for a symbol. Sure enough, the rdoc at <a href ttp://redmine.ruby-lang.org/repositories/entry/ruby-19/enum.c#L449">http://redmine.ruby-lang.org/repositories/entry/ruby-19/enum.c#L449</a> indicates such special treatment for Symbols as the sole argument and the error raised stems from the call to rb_to_id that occurs at line 507.<br> <br>Jacob Fugal<br> ------ art_37612_15120926.1225471974095--