[boost] property tree find no match for 'operator=='

Subject: [boost] property tree find no match for 'operator=='
From: Bernd Prager (bernd_at_[hidden])
Date: 2011-09-30 13:17:33

All,

This is likely to be a silly question.
I am trying to check for the existence of a value in a property tree.

Reading the docs I assumed the easiest way would be:

namespace pt = boost::property_tree;
static pt::ptree pt;

bool has(const std::string key) {
    if (pt.find(key) == pt.end()) return false;    // (1)
    return true;
}

The compiler complains about "error: no match for 'operator=='" in line
(1) though.
What am I missing?

Thank you for any help,
-- Bernd