Function json_parse 

pub fn json_parse(input: &str) -> Result<Value, String>

Parse a JSON string into a CJC Value.

Mapping:

• JSON null → Value::Void
• JSON bool → Value::Bool
• JSON number → Value::Float (or Value::Int if integer-valued)
• JSON string → Value::String
• JSON array → Value::Array
• JSON object → Value::Struct { name: "Json", fields } with sorted keys