While trying to build a set of higher-order search and 
match functions, I came across the "null at the front of 
the lambda name" refered to in bug #10721.

It would ne very neat if one could write:

function _not_($f) {
  return create_function('$x', "return !$f(\$x);");
}

and so on for _and_ and _or_(with two function args).  
Once a set of primitive match functions are defined you 
can then define complex criteria.  However, the parser 
rejects the names produced create_function.

The following works but it clearly yucky:

function f_not($f) {
  $f = substr($f, 1);
  return create_function('$x',
    "return !call_user_func(chr(0).'$f', \$x);");
}

For these lambdas to be true closures, they should be 
callable from other created functions.