Created OnDemand logic (markdown)

OnDemand-logic.md

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+## object
+
+When searching for a key, if the key is found then we are left pointing at the colon, and we are one depth below the object itself.
+
+If the key is not found then we are left pointing at the either the start of the object or else a comma.
+
+
+## depth
+
+
+The depth is set in the following functions:
+1. reenter_child
+2. abandon (sets the depth to 0)
+
+The depth is incremented in these instances:
+1. when encountering a colon in field_value()
+2. in started_array() when it is not an empty array. Note that started_object does not similarly increment the depth.
+3. in has_next_element() when encountering a comma. Note that a comma in an object does not change the depth (see has_next_field())
+
+The depth is decremented in these instances:
+1. When an object is closed by } (in started_object(), in has_next_field())
+2. When an array is closed by ] (in started_array(), in has_next_element())
+3. In advance_start(), in advance_root_scalar(), in advance_non_root_scalar()
+
+
+Skip child will, as a first step, decrement the depth when encountering },] or an atom (anything that does not start with [,{,:, or the comma), and then scan the structural elements, incrementing on [,{ and decrementing on },].