    Walker is my name
    and I am the same.
    Riddley Walker.
    Walking my riddels
    where ever theyve took me
    and walking them now
    on this paper the same.

from [Riddley Walker](http://en.wikipedia.org/wiki/Riddley_Walker) by Russell Hoban

---

Code may be data, but only some of that data is executable.  If we want to perform a pervasive code transformation, using something like `clojure.walk` presents a few problems:

* binding forms are treated the same as actual expressions
* `clojure.walk/macroexpand-all` will pass in a nil `&env` to all macros
* macroexpansion doesn't expand inlined functions

This means that transforms that we intend to apply to expressions may have unintended consequences on a `fn`, `let`, or `case` form.  It also means that any macro which relies on `&env` will not compose with our transformation.  Finally, if inlined functions aren't expanded, this can break certain transformations.

### usage

[![Build Status](https://travis-ci.org/ztellman/riddley.png?branch=master)](https://travis-ci.org/ztellman/riddley)

```clj
[riddley "0.1.12"]
```

Riddley provides a correct `riddley.walk/macroexpand-all`, which preserves the binding information in `&env` and expands inlined functions, and `riddley.walk/walk-exprs`, which is a general mechanism for code walking and transformation.

`walk-exprs` takes two arguments, a `predicate` for whether it should transform the sub-form, and a `handler` for doing the transformation.

```clj
riddley.walk> (walk-exprs number? inc '(let [n 1] (+ n 1)))
(let* [n 2] (. clojure.lang.Numbers (add n 2)))
```

Notice that `walk-exprs` implicitly macroexpands the form, including the inline form for `+`.  Unlike `clojure.walk`, if `handler` is called, sub-forms will not be walked.  The handler function is responsible for recursively calling `walk-exprs` on the form it's handed.

Access to `&env` is available via `(riddley.compiler/locals)` if you need it as part of your transformation.

Full documentation can be found [here](http://ideolalia.com/riddley/).

### license

Copyright © 2013 Zachary Tellman

Distributed under the MIT License.
