# zcl User Functions Extension

This zcl extension allows a calling application to support user-defined
functions.

Functions are defined via a specific block type, like this:

```zcl
function "add" {
  params = ["a", "b"]
  result = a + b
}
```

The extension is implemented as a pre-processor for `cty.Body` objects. Given
a body that may contain functions, the `DecodeUserFunctions` function searches
for blocks that define functions and returns a functions map suitable for
inclusion in a `hcl.EvalContext`. It also returns a new `cty.Body` that
contains the remainder of the content from the given body, allowing for
further processing of remaining content.

For more information, see [the godoc reference](http://godoc.org/github.com/zclconf/go-zcl/ext/userfunc).