From: Jaakko Jarvi (jarvi_at_[hidden])
Date: 2006-03-08 16:47:48
On Mar 8, 2006, at 3:21 PM, Scott Meyers wrote:
> Consider this (working) code using Boost.FileSystem:
>
> fs::directory_iterator di(dir);
> fs::directory_iterator end;
> while (di != end) {
> if (is_directory(*di)) cout << "D\n";
> else cout << "~D\n";
> ++di;
> }
>
> This looks like it should be lambda-able. Here's my attempt:
>
> for_each(fs::directory_iterator(dir), fs::directory_iterator(),
> if_then_else(bind(&fs::is_directory, _1),
> cout << "D\n",
> cout << "~D\n"));
>
> VC7.1 doesn't like this -- the diagnostics are below. Any idea how
> I can make
> this work?
>
I can spot one thing at least:
Arguments to if_then_else must be lambda functions:
> if_then_else(bind(&fs::is_directory, _1),
> var(cout) << "D\n",
> var(cout) << "~D\n"));
This delays the evaluation of the branches (which would otherwise
just print D or ~D once,
when the lambda function is created, rather than during every
iteration of for_each
Best, Jaakko