// a sketch of what the new API might look like #include "yaml-cpp/yaml.h" #include int main() { { // test.yaml // - foo // - primes: [2, 3, 5, 7, 11] // odds: [1, 3, 5, 7, 9, 11] // - [x, y] // move-like semantics YAML::Value root = YAML::Parse("test.yaml"); std::cout << root[0].as(); // "foo" std::cout << str(root[0]); // "foo", shorthand? std::cout << root[1]["primes"][3].as(); // "7" std::cout << root[1]["odds"][6].as(); // throws? root[2].push_back(5); root[3] = "Hello, World"; root[0].reset(); root[0]["key"] = "value"; std::cout << root; // # not sure about formatting // - {key: value} // - primes: [2, 3, 5, 7, 11] // odds: [1, 3, 5, 7, 9, 11] // - [x, y, 5] // - Hello, World } { // for all copy-like commands, think of python's "name/value" semantics YAML::Value root = "Hello"; // Hello root = YAML::Sequence(); // [] root[0] = 0; // [0] root[2] = "two"; // [0, ~, two] # forces root[1] to be initialized to null YAML::Value other = root; // both point to the same thing other[0] = 5; // now root[0] is 0 also other.push_back(root); // &1 [5, ~, two, *1] other[3][0] = 0; // &1 [0, ~, two, *1] # since it's a true alias other.push_back(Copy(root)); // &1 [0, ~, two, *1, &2 [0, ~, two, *2]] other[4][0] = 5; // &1 [0, ~, two, *1, &2 [5, ~, two, *2]] # they're really different } { YAML::Value node; // ~ node[0] = 1; // [1] # auto-construct a sequence node["key"] = 5; // {0: 1, key: 5} # auto-turn it into a map node.push_back(10); // error, can't turn a map into a sequence node.erase("key"); // {0: 1} # still a map, even if we remove the key that caused the problem node = "Hello"; // Hello # assignment overwrites everything, so it's now just a plain scalar } { YAML::Value map; // ~ map[3] = 1; // {3: 1} # auto-constructs a map, *not* a sequence YAML::Value seq; // ~ seq = YAML::Sequence(); // [] seq[3] = 1; // [~, ~, ~, 1] } { YAML::Value node; // ~ node[0] = node; // &1 [*1] # fun stuff } { YAML::Value node; YAML::Value subnode = node["key"]; // 'subnode' is not instantiated ('node' is still null) subnode = "value"; // {key: value} # now it is YAML::Value subnode2 = node["key2"]; node["key3"] = subnode2; // subnode2 is still not instantiated, but node["key3"] is "pseudo" aliased to it subnode2 = "monkey"; // {key: value, key2: &1 monkey, key3: *1} # bam! it instantiates both } { YAML::Value seq = YAML::Sequence(); seq[0] = "zero"; // [zero] seq[1] = seq[0]; // [&1 zero, *1] seq[0] = seq[1]; // [&1 zero, *1] # no-op (they both alias the same thing, so setting them equal is nothing) Is(seq[0], seq[1]); // true seq[1] = "one"; // [&1 one, *1] UnAlias(seq[1]); // [one, one] Is(seq[0], seq[1]); // false } { YAML::Value root; root.push_back("zero"); root.push_back("one"); root.push_back("two"); YAML::Value two = root[2]; root = "scalar"; // 'two' is still "two", even though 'root' is "scalar" (the sequence effectively no longer exists) // Note: in all likelihood, the memory for nodes "zero" and "one" is still allocated. How can it go away? Weak pointers? } { YAML::Value root; // ~ root[0] = root; // &1 [*1] root[0] = 5; // [5] } { YAML::Value root; YAML::Value key; key["key"] = "value"; root[key] = key; // &1 {key: value}: *1 } { YAML::Value root; root[0] = "hi"; root[1][0] = "bye"; root[1][1] = root; // &1 [hi, [bye, *1]] # root YAML::Value sub = root[1]; // &1 [bye, [hi, *1]] # sub root = "gone"; // [bye, gone] # sub } return 0; }