Anatomy of a Function

The following are all the predicates that you can specify when creating a function.

Predicate	Type	Description
name	string	Function name
params	(multi) string	List of parameters this function supports.
code	string	Actual ledger code
doc	string	A docstring for this function.
language	string	Programming language used (not yet implemented, currently only Clojure supported)
spec	JSON	(not yet implemented) Optional spec for parameters. Spec should be structured as a map, parameter names are keys and the respective spec is the value.

In the next lesson, we'll be talking a lot more about _fn/code, but for now take a look at an example function, which subtracts 3 from a value:

[
  {
    "_id": "_fn",
    "name": "minus3",
    "params": ["a"],
    "code": "(- a 3)",
    "doc": "Subtracts 3 from a value, a"
  }
]

As you can see above, our code takes a parameter, a. We declare a in _fn/params, and we can therefore use it in our code.