api.cpp

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// a sketch of what the new API might look like

#include "yaml-cpp-pm/yaml.h"
#include <iostream>

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<std::string>(); // "foo"
                std::cout << str(root[0]); // "foo", shorthand?
                std::cout << root[1]["primes"][3].as<int>(); // "7"
                std::cout << root[1]["odds"][6].as<int>(); // 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;
}