Why can't we set vector type parameters from strings via Parameter, only ParameterApplicator?

[timsnyder]

in template<class ValueType> template<class T, class C1> inline std::enable_if<sparta::is_vector<C1>::value>::type sparta::Parameter<ValueType>::setValueFromString_(const std::__cxx11::string &str, bool poke = false)
at

map/sparta/sparta/simulation/Parameter.hpp

Lines 2317 to 2319 in ee08219

	throw ParameterException("Cannot set value from string on parameter \"")
	<< getName() << "\" which is a vector type \""
	<< getTypeName() << "\"";

Why throw?

Couldn't we just move the code from:

map/sparta/sparta/app/ConfigApplicators.hpp

Lines 331 to 355 in ee08219

	// Parse the string as YAML and assign it to this node
	ParameterTree ptree;
	sparta::ConfigParser::YAML::EventHandler handler("<command line>",
	{p},
	ptree,
	{},
	verbose);
	// These parameters will be in the unbound list first
	// and then applied later where it MUST match existing nodes
	handler.allowMissingNodes(false);
	std::stringstream input(value_);
	YP::Parser parser(input);
	while(parser.HandleNextDocument(*((YP::EventHandler*)&handler))) {}
	if(handler.getErrors().size() != 0){
	sparta::SpartaException ex("One or more errors detected while parsing "
	"command line parameter values.\n"
	"Attempting to intrerpret YAML value '");
	ex << value_ << "' at " << p->getLocation() << "\n";
	for(const std::string& es : handler.getErrors()){
	ex << es << '\n';
	}
	throw ex;
	}

into Parameter instead of throwing an exception and this would enable programmatically taking a string with a nested vector representation and setting a parameter with it just like we do via cmdline -p?

In other words, should the logic for YAML parsing the string and applying it to N-dimensional Vector move into Parameter and remove the if if(false == p->isVector()) from ParameterApplicator.

[timsnyder]

Well, the first reason I'm encountering is that simply moving the use of sparta::ConfigParser::YAML::EventHandler into Parameter.hpp creates a circular include because ConfigParserYAML.hpp includes Parameter.hpp because it was written to populate a ParameterTree
during the parsing. In the case of ParameterApplicator, the ptree passed into the handler is thrown away (because it doesn't really make sense to assign a full yaml tree to -p <some node path>.

It seems like sparta::ConfigParser::YAML::EventHandler would need to be reorganized a bit so that a specialization that only parses legal parameter values (but not keys or an entire tree) can be used from Parameter without causing the circular includes.