[Heaps] Compiler error: ‘optional’ was not declared in this scope

Subject: [Heaps] Compiler error: ‘optional’ was not declared in this scope
From: Phil Endecott (spam_from_boost_dev_at_[hidden])
Date: 2011-06-07 14:51:11

Dear All,

I'm trying to do some simple tests with the proposed Heaps library, but 
I get a mountain of compiler errors that start like this:

./boost_heap-HEAD-449f378/boost/heap/priority_queue.hpp:32: error: 
‘optional’ was not declared in this scope
./boost_heap-HEAD-449f378/boost/heap/priority_queue.hpp:32: error: 
template argument 1 is invalid
./boost_heap-HEAD-449f378/boost/heap/priority_queue.hpp:32: error: 
expected unqualified-id before ‘,’ token

I thought this was probably due to me having a too-old boost 
installation, but I believe I'm now compiling with 1.46.1 and I get the 
same error (though I need to verify that my paths are all set 
correctly).  Any ideas anyone?

(I've arrived late to this review having been away, but I'd like to do 
some quick benchmarks if I have time.)

Thanks,  Phil.